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Food Research International 51 (2013) 729–747

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Food Research International

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Review

Diverse food-based applications of nuclear magnetic resonance (NMR) technology

Massimo F. Marcone a,⁎, Sunan Wang a, William Albabish a, Shaoping Nie b, Dinesh Somnarain a, Art Hill a

a Department of Food Science, University of Guelph, 50 Stone Road East, Guelph, Ontario, Canada N1G 2W1b State Key Laboratory of Food Science and Technology, Nanchang University, 235 Nanjing East Road, Nanchang, Jiangxi Province, 330047, China

⁎ Corresponding author. Tel.: +1 519 824 4120x5833E-mail addresses: [email protected] (M.F. Ma

0963-9969/$ – see front matter © 2013 Elsevier Ltd. Allhttp://dx.doi.org/10.1016/j.foodres.2012.12.046

a b s t r a c t
a r t i c l e i n f o
Article history:Received 15 December 2011Accepted 21 December 2012

Keywords:Nuclear magnetic resonance (NMR)Magnetic resonance imaging (MRI)Foods

Nuclear magnetic resonance (NMR) spectroscopy is one of the most common investigative techniques usedby both chemists and biochemists to identify molecular structures as well as to study the progress of chem-ical reactions. Magnetic resonance imaging (MRI), another type of NMR technology, has extensively beenused in medical radiology to obtain soft tissue images for diagnostic purposes in medicine. Food scientistshave also explored the use of both NMR and MRI and continue to develop a wide range of applications forfood analysis and food processing. This review begins with a brief introduction to NMR and then focuseson current diverse NMR applications in food research and manufacturing. Topics covered include chemicalcompositional analysis and structural identification of functional components in foods, determination ofcomposition and formulation of packaging materials, detection of food authentication, optimization of foodprocessing parameters, and inspection of microbiological, physical and chemical quality of foods. This reviewalso emphasizes the pros and cons of specific NMR applications in the analysis of representative foods such aswine, cheese, fruits, vegetables, meat, fish, beverages (i.e. tomato juice and pulp, green tea, coffee) and edibleoils, as well as discussing both the challenges and future opportunities in NMR applications in food science.

© 2013 Elsevier Ltd. All rights reserved.

Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7302. Potential applications of NMR/MRI for compositional analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 730

2.1. Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7302.2. Fat and fatty acids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7322.3. Protein/amino acids (AAs) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 733

3. Potential applications of NMR/MRI for structural analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7334. Potential applications of NMR/MRI for inspection of microbiological, physical and chemical quality of foods . . . . . . . . . . . . . . . . . 7345. Application of NMR in food packaging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7356. Potential application of NMR/MRI in food authentication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 735

6.1. Honey . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7356.2. Salmon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7356.3. Olive oil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7366.4. Beverages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 736

7. Potential applications of NMR/MRI for on-line monitoring of food processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7368. Specific NMR/MRI applications to some representative foods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 737

8.1. Wine and beer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7378.2. Fruit and vegetable juice and pulp, green tea, and coffee . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7378.3. Edible oils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7428.4. Cheese . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7428.5. Fruits and vegetables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7428.6. Meat and fish . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 743

9. Conclusion and future research . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 743References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 744

4; fax: +1 519 824 6631.rcone), [email protected] (S. Wang).

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730 M.F. Marcone et al. / Food Research International 51 (2013) 729–747

1. Introduction

Nuclear magnetic resonance (NMR) can be applied to a widerange of liquid and solid matrices without altering the sample or pro-ducing hazardous wastes. Although the sensitivity and detectionlimits of NMR still need to be improved, NMR still has several advan-tages relative to other common analytical tools such as high pressureliquid chromatography (HPLC), gas chromatography (GC) and massspectrometry (MS).

NMR technology was initially used in the late 1940s to elucidate thestructure of molecules in organic chemistry (Gutowsky, Kistiakowsky,Pake, & Purcell, 1949). However the diverse applications of NMR spec-troscopy in food science were delayed until the 1980s, primarily dueto lack of scientific expertise, high cost of equipment, and the absenceof NMR parts designed specifically for food purposes, although pulsedNMR had been applied to foods and related materials earlier than this.With the development of NMR instrumentation and improved pro-grams to collect and analyze the data, NMR's applicability has recentlyrapidly expanded in the field of food science and technology. A widerange of NMR food-related research has covered various fields of foodscience, including food microbiology, food Chemistry, food engineeringand food packaging (as shown in Table 1) (Belton, Engelsen, & Jakobsen,2005; Chen et al., 2010; Nestor et al., 2010; Vilen et al., 2010). As illus-trated in Fig. 1, the numbers of these studies are dramatically increasedin recent years.

A solid background with regards to NMR principles has been welldocumented (Belton, Gil, Webb, & Rutledge, 2003; Belton et al., 2005;Engelsen, Belton, & Jakobsen, 2005; Farhat, Belton, & Webb, 2007;Gudjonsdottir, Belton, & Webb, 2009; Hills, 1998; Renou, Belton, &Webb, 2011; Webb, Belton, Gil, & Delgadillo, 2001). Nowadays, NMRanalysis is often based on the behavior (relaxation) ofNMR active nuclei(i.e. 1H, 13C which are the most widely used for food applications) in amagnetic field and a pulsed Radio Frequency (RF) irradiation. Relaxa-tion describes a complex process of the nuclei from excitation [due tosplitting of the nuclear spin levels (Zeeman effect) by applied magneticfield] to equilibrium (Novoa-Carballal, Fernandez-Megia, Jimenez, &Riguera, 2011).

Based on the principle of NMR, magnetic resonance imaging (MRI)further permits visual observation of the interior of foods. MRI offersnot only information about the chemical composition and internalstructure of certain foods, but also permits monitoring of internalcompositional and structural modification of foods when they experi-ence different agricultural practices (i.e. harvest, postharvest) andindustrial possessing. The former would automatically expand the

Table 1Example of NMR spectroscopy applications in specific topics of food science.

Selected application Representative Examples

Quantitative analysis Water/moisturecontents

Soybean

Lipid (fatty acid) Arctic charHeifers meatBeef, chicken and porkMilkMustard seeds and rapeseeds

Protein (amino acid) Orange and grapefruits juiceMustard seeds and spring rape

Conformational analysis Polysaccharides Carrageenan gumNutritional or functional aspects Metabolites Green tea

Isoflavones Methanolic soybean extractPackaging materials Irradiation PolymerQuality Control Authenticity Virgin olive oil

Food additives Banned dyes–Sudan dyesProcess control Rheology Wheat doughs

Salting and storing Wild and farmed Atlantic cod(Gadus morhua)

capability of currently available on-line food quality sorting method-ologies, which have typically only been used to monitor externalproperties such as color, size, shape or externally visible defects(Chayaprasert & Stroshine, 2005). The latter would provide a betterunderstanding of the impacts of these external factors on thephysiochemical properties (Herrero et al., 2007; Renou, Foucat, &Bonny, 2003).

The progress in research of NMR use on foods has been addressedin several recent reviews with a limited scope focusing on NMRapplications either in particular foods, such as wine (Ogrinc, Kosir,Spangenberg, & Kidric, 2003); dairy foods (Mariette, 2009) or specificapplications, such as identification of food authenticity (Mannina &Segre, 2002) and investigation into the correlations between waterdistribution and mobility, water holding capacity and meat quality(Pearce, Rosenvold, Andersen, & Hopkins, 2011), or assessment orinspection of the quality parameters of fruits (Butz, Hofmann, &Tauscher, 2005). Due to the importance and versatility of NMR/MRIapplications in food science and technology, a comprehensive reviewwould help to identify future trends of NMR application in foodscience.

This review provides a comprehensive summary of diverse applica-tions of NMR in both food research andmanufacturing, followed by de-tailed information on the use of NMR in certain foods (i.e. wine, cheese,fruit, vegetable, meat, fish, tomato juice, pulp, green tea, coffee, oil).

2. Potential applications of NMR/MRI for compositional analysis

Due to the fact that many foods are proton-rich, with protons origi-nating, e.g., from water, fat, carbohydrates, and proteins; proton NMRbecomes the most common type of NMR to determine these abundantfood components. The components are essential for human nutritionand also influence the intrinsic properties of food during processing,storage, and transportation.

2.1. Water

In NMR spectroscopy, the signal of water in food samples has beenfrequently investigated for the determination of water content andwater distribution in foods (Butz et al., 2005; Ciampa, Dell'Abate,Masetti, Valentini, & Sequi, 2010; Otero & Préstamo, 2009; Pearce etal., 2011; Sequi, Dell'Abate, & Valentini, 2007). In fact, magnetic reso-nance imaging (MRI) permits visual observations of the spatial andmolecular distribution of water with its food matrix environment.For example, MRI offers visualized bi-dimensional and partial image

States of food Reference

Liquid Solid

X Chen et al. (2010)

X Nestor et al. (2010)X Ballerini et al. (2002)X Keeton et al. (2003)

X Hu, Furihata, Kato, and Tanokura (2007)X Pedersen, Munck, and Engelsen (2000)

X Belton et al. (1996)seeds Pedersen et al. (2000)

X Vilen, Lundqvist, Jouanneau, Helbert, and Sandstrom (2010)X Lee et al. (2010)X Caligiani, Palla, Maietti, Cirlini, and Brandolini (2010)

X Pentimalli et al. (2000)X Alonso-Salces et al. (2010)X Di Anibal, Callao, and Ruisánchez (2011)

X Lopes-da-Silva, Santos, Freitas, Brites, and Gil (2007)X Gudjonsdottir et al. (2010)

Fig. 1. The distribution of scientific publication regarding the applications of NMR in the field of food science and Technology in ISI web of science during 1971–2011 (adapted datefrom citations).

731M.F. Marcone et al. / Food Research International 51 (2013) 729–747

on internal morphological organization of certain foods (such as highwater content foods). The intensity of the signal in the various zonesof the sample may be directly proportional to water molecule con-tent. Specifically, darker areas in an image may mean that there areless water/protons. The area could contain a high concentration ofions and or contrast agent, etc. which enhances relaxation, causingthe area to become darker (Butz et al., 2005).

The use of MRI also permits the quantification of water contentand water distribution by magnetic resonance parameters (i.e., T1and T2), which provide information about physical (distribution,compartmentalization) and chemical (mobility, interactions withmacromolecules) water properties. By repetitive measures of thesame samples, MRI can detect variations in the water concentration,as well as changes in water interaction with cellular tissues of thesefoods. This variation may associate with maturity, damage, decay, orother quality related factors of fruits and vegetables (Butz et al.,2005). Variations may also be caused by various factors, such as envi-ronmental and climate conditions in which the raw materials wereproduced, and the processing of these raw materials into food prod-ucts (Butz et al., 2005; Ciampa et al., 2010; Otero & Préstamo, 2009;Pearce et al., 2011; Sequi et al., 2007).

Most recently, MRI results illustrated the importance of changesoccurring in water content among cherry tomatoes according to theseason (i.e. winter, spring and summer) (Ciampa et al., 2010), all ofwhich impact their shelf life and storage conditions. MRI providedinformation about water content and its spatial organization in thedifferent zones of cherry tomatoes. NMR parameters (T2 and T1)were measured in the cellular tissues (i.e. pericarp and endocarp) ofPachino cherry tomato fruits. Variations of T1 and T2 representedthe change of water molecular motion and its distribution withinthe fruit, caused by seasonal variations (summer, spring and winter)(Ciampa et al., 2010). On the basis of the information regardingwater content and its distributions within the product, geographicalplace of cultivation could be distinguished among 70 cherrytomatoes (Sequi et al., 2007). In yet another study, different impacts

of pressure processing (i.e. pressures of 100 and 200 MPa) on thequality of strawberry products were also found (Otero & Préstamo,2009).

In order to determine the accuracy and precision of NMR-basedwater content determination techniques, comparative studies havebeen carried out. Keeton et al. (2003) compared the moisture con-tents obtained by NMR analysis for meat products, including beef,deboned chicken with skin, pork, and all-beef hot dogs, with thoseobtained using the AOAC officially described analytical methodswhich consisted of forced air oven drying. The NMR results for mois-ture in beef, chicken, and pork were 40.42%, 74.37%, and 73.75%, re-spectively, being in good agreement with those obtained usingAOAC Official Methods (i.e. 40.39%, 74.57%, and 73.94%, respectively)(Keeton et al., 2003).

2D MRI was also used successfully to monitor moisture transpor-tation in two different multicomponent food systems: one had alow water activity contrast that results in a slow moisture transport(hours), another one had a high water activity contrast that resultsin a fast moisture transport (days) (Ramos-Cabrer, Van Duynhoven,Timmer, & Nicolay, 2006).

It should be noted that the signal through the MRI studies of thewater content of food samples comes directly from the water signalof the sample, except in those samples that have a high content infatty acids. However, if the component of interest has much lowerconcentration in the foods, the water must be presaturated, sincethe strong water signal overlaps the signal of other interesting com-ponents. Presaturation is one of the widely used ways to eliminate astrong solvent signal (i.e. water signal), in which a long low-powerpulse is applied on the solvent (water) resonance as part of thepulse. After saturating the solvent (water) resonance at the transmitterfrequency, a non-selective pulse with a wide excitation profile) is thenapplied to place all remaining spins in the transverse plane fordetection. It should also be noted that due to the complexity of foodstuff, research regarding foodwater interactions have been heavily con-centrated inmodel systems, such as using protein hydration as a model


for foodstuffs, which have been well summarized in a recent review byBelton (2011).

2.2. Fat and fatty acids

The capability of NMR spectroscopy for fat analysis of differentfoods includes not only for determining total fat contents but alsofor identifying fatty acid composition of the fat. Up to date, NMR hasbeen dedicated to fat and oil quantification in a variety of agri-foodproducts (i.e. animal and vegetable oil and fat). Colnago, Azeredo,Marchi Netto, Andrade, and Venâncio (2011) well demonstrated rel-evant theories and concepts.

1H NMR with a presaturation method to suppress the signal ofH2O has successfully determined the fat contents in their milk sampleto be 3.6±0.1% (Hu et al., 2007). The value obtained by NMR was ingood agreement with that determined by the Rose–Gottlieb method,which determines fat content by gravimetric analysis after fat extrac-tion with diethyl ether (ethoxyethane) (Hu et al., 2007).

In order to quantify more compounds in milk, quantitative 2DNMR experiments, were further performed, since the 1H NMR spec-trum of milk was very crowded, and many signals overlapped. 10%D2O was added to milk to adjust the NMR lock and shim systemand to obtain good 1H–13C HSQC (heteronuclear single quantum co-herence) spectra. The resulting spectrum is two-dimensional (2D)with one axis for 1H and the other for 13C. This 2D NMR permits quan-tification of milk compounds, which may be overlapping, or weak sig-nals in the 1H NMR spectra. Considering the addition of D2O to milk,concentrations of milk compounds were compensated during thedata processing. 1H–13C HSQC 2D NMR spectra revealed unsaturatedfatty acids (0.9 mMmonounsaturated fatty acids and 0.3 mM polyun-saturated fatty acid) as well as 24.0 mM saturated fatty acid. The fattyacid content determined by 1H–13C 2D NMR seemed higher than thatobtained by gas chromatography which could be due to the losses inthe sample pre-treatment for GC analysis.

Gas chromatography (GC) has traditionally been used as a recog-nized analytical technique for fatty acid analysis and thus has been fre-quently used to validate NMR analysis results. Miyake, Yokomizo, andMatsuzaki (1998) compared the results from 13C-NMR (300 MHz)and GC for the n−6 polyunsaturated fatty acid composition in palm,olive, safflower and corn oils. NMR analysis revealed that the variousoils contained 11.2%, 14.3%, 43.7% and 60.2%, respectively, while GCyielded results of 13.5%, 15.5%, 44.9% and 60.6% respectively, whichare in a very close agreement (Miyake et al., 1998).

Igarashi (2000) also reported that a good correlation existed be-tween 1H-NMR (500 MHz) data and those obtained by GC in the de-termination of the n−3 fatty acid content in unrefined bonito andtuna oils produced in Japan, and also in salmon oil produced inNorway. They observed that a good correlation (R2=0.994, relativeerror b5%) existed between the 1H-NMR data and the GC data, withregard to the molar proportions of DHA to DHA quantification withethylene glycol dimethyl ether (EGDM) (an internal standard). Onceagain, the use of NMR appears to be a very promising tool for fattyacid analysis of foods (Igarashi, 2000).

Besides GC, fat content analysis by NMR/MRI was also very compa-rable to other analytical assays. Fat content in eight heifer longissimusdorsi muscle slices (2 mm thick) was determined with MRI byBallerini et al. (2002). By improving image by a segmentation methodand selected median filters in their study, MRI was successful inmeasuring the fat percentage and its distribution in the sample, withthe mean fat content determined by MRI having a good correlationwith the results obtained by chemical analysis. Although the re-searchers did not specify what kind of chemical analysis was used intheir paper, they successfully employedMRI for quantitative evaluationof fat percentage in a visual, fast and non-destructive manner (Balleriniet al., 2002).

Additionally, NMR results for the fat content in beef, chicken andpork were 46.00%, 7.15%, and 3.88%, respectively, these results beingin agreement with those obtained by Soxhlet ether extractionmethods, namely 45.84%, 7.24%, and 3.74% respectively (AOAC OfficialMethod 960.39) (Keeton et al., 2003). This observation proved thatfat content analysis from NMR was also very comparable to theabove mentioned AOAC methods (Keeton et al., 2003). In anotherstudy, Ruan, Chang, Chen, Fulcher, and Bastian (1998) reported thatthe MRI derived moisture content of cheese slices was 39.9%±0.5%,which corresponded closely to the results (39.8%±0.3%) obtainedby the official oven-drying method for cheese slices (Ruan et al.,1998). It has also been found that fat content of minced pork samplesby NMR agreed with results by Fosslet fat analyzer (AOAC OfficialMethod 976.21) (Sorland, Larsen, Lundby, Anthonsen, & Foss, 2005).

Measurements from three non-destructive methods (NIR, NMRand Fatmeter) were used to determined lipid contents of herring(Clupea harengus L) from both a Danish research vessel and commer-cial catches. Specifically, Fatmeter measurements were conducted inthe frequency range of microwave radiation (i.e. 2 GHz–720 MHz).NIR spectra were measured with an InfraProver, II Fourier transformspectrometer at region from 4500 to 9996 cm−1. NMR measure-ments were performed on a Maran Benchtop Pulsed NMR analyzerat 23.2 MHz. After comparing results from the three above methods(i.e. NIR, NMR, and Fatmeter), researchers concluded that Fatmeterappeared to have the lowest cost per analysis and can be operatedafter basic training, but is not suited for measurements of whole her-ring. NMR appeared to be the most expensive technique, yet MRI wasthe most suitable for measurements of whole herring with thehighest precision therefore holding the highest potential as a produc-tion line measurement for sorting the rawmaterial into more homog-enous batches of foods (Nielsen, Hyldig, Nielsen, & Nielsen, 2005).Conversely, NIR was found to lie in between the two methods men-tioned above in terms of cost and applicability (Nielsen et al., 2005).

Since no particular method is perfect, the combination of NMRwith other analytical methods may give better analytical results.Keeping this in mind, NMR has been combined with micro-oven dry-ing methods for the rapid determination of moisture and fat in bothraw and processed products, including five primary meat categories(such as beef, chicken, pork, ham, and turkey). Researchers furtherquantified the performance of such combinations. NMR results werecompared with results obtained by AOAC moisture determinationMethods 950.46 (Forced Air Oven Drying) and AOAC fat determina-tion Method 960.39 (Soxhlet Ether Extraction). NMR combined withmicro-oven drying methods yielded much more consistent resultswith these AOAC methods compared to each method performedalone (Leffler et al., 2008).

Since 1993, NMR has become an AOCS Official Method (AmericanOil Chemists' Society, 2004), to determine solid fat contents (SFC) offats and oils in the food industry, particularly in the bakery, confection-ery and margarine industries (Campos, Ollivon, & Marangoni, 2009;Marangoni & Rousseau, 1995; Timms, 2003; Vereecken, Foubert,Smith, Sassano, & Dewettinck, 2010). Solid fat content (SFC) refers toa solid/liquid ratio of lipid at various temperatures. Many properties offoods containing lipid, such as spreadability, firmness, mouthfeel, pro-cessability and stability of margarine and butter, are associated withSFC.

In some cases, SFC results lead to further information about theproperties of lipids, such as polymorphism and crystallization. In astudy on the graininess phenomenon, beef tallow (BT)-based short-ening was exposed to temperature fluctuation cycles of 5–20 °C to in-duce granular crystals. This leads to the graininess phenomenonreferring to an unexpected growth of granular crystals in such fatproducts as shortenings and margarines, which ultimately impairthe consistency and plasticity of these fat products and it is consid-ered as a structural defect of fat products. NMR analyzer was success-ful in determining SFC of BT-based shortening and further obtaining


the isothermal crystallization behavior of the surrounding materialsand granular crystals based on SFC. Such results not only demonstrat-ed the possibility of NMR to determine SFC, but also to monitor somestructural defects like the graininess phenomenon.

A combination of 1H NMR and 13C NMR was able to provide in-sights into triacylglycerol polymorphs, which include α, β′ and βpolymorphs, which in turn influence the quality of final products(Adam-Berret, Rondeau-Mouro, Riaublanc, & Mariette, 2008). 1HNMR provided discrimination between α and β polymorphs by mea-suring proton spin–lattice or spin–spin relaxation times, which wasfurther confirmed by high-field 13C NMR by obtaining relaxation in-formation on each triacylglycerol carbon site.

Additionally, 1H NMR holds a possibility for determining thequality of foods according to results based on fat compositionalanalysis. 1H NMR spectral data allowed visualizing the compositionalchange of virgin olive oil at room temperature while protected fromlight. The presence and intensity of 1H NMR signals of some targetedchemicals (i.e., hydroperoxide) permit a stability evaluation of thisvirgin olive oil. The presence of hydroperoxide (primary lipid oxida-tion products) indicated that oxidative degradation of virgin oliveoil occurred. Such an approach to investigate the oxidation processof edible oils or meat fat was reported by other investigators(Guillén & Ruiz, 2001, 2006; Stefanova, Vasilev, & Vassilev, 2011).On the other hand, NMR results can also provide stock breeding infor-mation. Genetic selection of chicken was based on NMR fat composi-tional analysis of abdominal fat and total body fat of chicken(Jaturasitha, Srikanchai, Kreuzer, &Wicke, 2008). 1H NMR spectral re-sults were also able to reveal the relationship between gamma-ray ir-radiation (at doses of 0.5, 2.5, 5.0, 7.5, 10.0, and 15.0 kGy) and fattyacid compositions of irradiated chicken meat, thereby permitting apossibility of NMR to monitor the irradiation processing via changesof fatty acid compositions in foods (Stefanova et al., 2011). All theabove studies using NMR for the characterization and quantitationof fat have served as ample evidence of the diversity, efficiency andspecificity of NMR for such determinations.

2.3. Protein/amino acids (AAs)

The amino acid profile is considered an important component af-fecting the characteristics of protein-based food. These characteristicsare nutrient values, thermal stability and functional properties toname a few. 1H NMR holds out the possibility of investigating thetotal quantity of protein in foods as well. For instance, Pedersen etal. (2000) found that the mean of protein contents in 17 wintermustard seeds and 20 spring rapeseeds were 28.02% and 20.80%, re-spectively, by means of low-field 1H nuclear magnetic resonance(LF-NMR) (Pedersen et al., 2000). NMR can also be used to furtherlook at the amino acid composition of food. For example, Consonni,Cagliani, Guantieri, and Simonato (2011) found that several aminoacids have distinct 1H NMR spectral peaks when testing Amaronewine, including leucine at 0.88, 1.44, and 3.37 ppm, threonine at1.42 and 4.38 ppm, alanine at 1.45 and 3.65 ppm, proline at 2.01,2.08, 2.35, 3.38, and 4.11 ppm and choline at 3.20 ppm (Consonni etal., 2011). This data permits the use of NMR to investigate vintageand aging effects on foods based on the changes of those compoundsand others (i.e. sugars, and aromatic compounds).

In another comparison study, Belton et al. (1996) applied NMR toinvestigate the amino acid profiles in a variety of fruit juices and vin-egar. The mean ratio of alanine to arginine in grape varieties was 1.8which is similar to published data obtained from other methods, withsimilar results also found in orange juice and grapefruit juice. Theonly exception is that c-aminobutyric acid was around half theexpected value than that from the published data. Again, NMR cansuccessfully provide rapid measurements when dealing with largesample sizes (Belton et al., 1996).

3. Potential applications of NMR/MRI for structural analysis

The use of NMR relaxation time not only permits compositionalanalysis of foods, but also insights into food structure. In MRI, theNMR relaxation time allows for quantification of the image contrast,therefore enabling visualized monitoring of structural changes infoods during processing and storage. Information obtained from thisdata often lead to the determination of the desired structures,which could impact the final physical and mechanical properties offood. Two major subjects studied by NMR/MRI include 1) structuralelucidation of specific food compounds; 2) quantification of micro-structural changes occurring in foods.

Several reviews have collectively well-documented primaryresearch on the first subject (i.e. structural elucidation of specific foodcompounds). A variety of foods have been targeted in these reviews,including carbohydrates (i.e., carrageen from Gigartina lanceataand G. chapmanii (Falshaw & Furneaux, 1998) or from bacteriaSolieria chordalis, Cystoclonium purpureum, Calliblepharis jubata andCalliblepharis ciliat (Deslandes, Bodeaubellion, Floch, & Penot, 1990).These reviews also covered chitin and chitosan (Kumirska et al.,2010), food colloids (Mariette, 2009), annatto food coloring (E160b)(Scotter, 2009), betanidin (a aglycon of the red-violet beet pigmentbetanin) (Mabry, 2001), and cellulose and its derivatives (Kono et al.,2002). In another study, diterpene phenols and other phenolic com-pounds from spices, such as rosemary and sage (Ho, Wang, Wei,Huang, & Huang, 2000), were reported. Until now, NMR techniquescontinue to garner scientific interest in the identification and structuredetermination of food compounds in a variety of foods. Some represen-tative examples of structural studied food compounds includefructooligosaccharides from roots and leaves of Stevia rebaudiana(Bert.) Bertoni (de Oliveira et al., 2011); Aminoreductone (AR) foundin heated Long-life (LL) milk and lactose–a-lactalbumin model system(Shimamura, Kurogi, Katsuno, Kashiwagi, & Ukeda, 2011), chitosanand carboxymethyl starch tablets (Wang, Assaad, Ispas-Szabo,Mateescu, & Zhu, 2011). With the concept that the properties of foodsis from a network of different components rather than a single compo-nent, NMR has also been exploited for structural investigation of com-plex food components, such as tea polyphenols (TP) with oat β-glucan(Wu et al., 2011).

In terms of the second subject (i.e., quantification microstructuralchanges of foods), most recently, a review by Mariette (2009) welldocumented the possible applications of low field magnetic fieldspectrometers (frequencies b25 MHz) for investigating the composi-tion and microstructural changes in a variety of foods under differentprocessing or storage conditions (Mariette, 2009). Both NMR relaxa-tion (one, two and multidimensional NMR) and diffusometry arewell documented. The NMR relaxation behavior of components in-cludes solid, liquid-like relaxation, solid and liquid fat relaxation, icerelaxation, biopolymer relaxation, and water relaxation. In terms ofwater relaxation, if the diffusion coefficient is slow compared to therelaxation rate, water relaxation (i.e., T2) behavior (multi-exponen-tial) has been used as a probe of the microstructure or to quantifythe water holding capacity of foods. The microstructural changes di-rectly influence the final functionality of these foods and ultimatelytheir sensory properties (Mariette, 2009). On the other hand, insamples where the diffusion coefficient is fast compared to therelaxation rate, water relaxation behavior (average and a singlemono-exponential) has been extensively investigated in studies ofchanges in macromolecular food structure resulting from processingoperations (Mariette, 2009). Foods that have been reviewed includeice cream, cake, whipped creams, cheese, potato, bread, milk, eggs,and chocolate (Mariette, 2009).

Keeping these applications in mind, Oztop et al. (2010) selected awhey protein-based gel to serve as a delivery model system for foods,and NMR spectrometry was employed to monitor spatial distributionof water in whey protein-based gels during swelling at a pH of 2.5, 7,


and 10 solutions. MRI demonstrated a distinct spatial distribution ofwater in whey protein-based gels during swelling at the three differ-ent pHs. They found that the diffusion of water into gels causes moresignificant microstructural changes in the gel at lower pH of 2.5 thanthat at higher pH. These results prove MRI/NMR to be a potentialtechnique to monitor and improve the understanding of swelling ofwhey protein gels or other properties of other delivery systems(Oztop et al., 2010).

The study of the crystalline structures of starch is another applica-tion for NMR/MRI. Different crystalline structures that are found instarch from different food sources include A-type, B-type, C-type andV-type crystalline structures. Knowing the crystalline structure of starchallows for the identification of the botanical origins of the starch. A-typecrystalline structure is commonly derived from cereal starch likecorn, wheat or rice, with amylopectin having short lateral chains andbranching points close to each other; B-type crystalline structure is usu-ally derived from fruits and tuber starches with amylopectin havinglong side chains and distant branching points. Whereas C type starchis a crystalline structure of a mixture of A and B-type crystalline struc-tures and is usually found in legumes (i.e. pea). On the other hand,V-type starch crystalline structure is derived from modified starch orendosperm of some native starch granules. 13C CP/MAS NMR spectros-copy (75.46 MHz) has been reported to be able to distinguish thesecrystalline structures of starch, therefore demonstrating the possibili-ties of NMR spectroscopy in identifying the origins of starches, as wellas well as providing insights into the changes of these crystalline struc-tures under different processing conditions (Barsby, Donald, & Frazier,2001; Therien-Aubin & Zhu, 2009).

1H-NMR spectroscopy has also successfully directed the structuralcharacterization in the denatured states (A-state) of α-lactalbumin, amajor whey protein in cow milk (Alexandrescu, Evans, Pitkeathly,Baum, & Dobson, 1993). The NMR spectrum of α-lactalbumin in theA-state had intense chemical shift dispersions with random coil confor-mation indicating that most of the long-range tertiary structure of theA-state is more disordered and nonspecific. These results, however,disagreed with other publications (Dolgikh et al., 1981; Ewbank &Creighton, 1991; Semisotnov et al., 1991). This study demonstrated amechanism by which an unstructured polypeptide chain folds, specifi-cally tertiary interactions and non-native structure in the A-state. Thestructural information such as the mechanisms for protein folding isconsidered crucial to the onset of various diseases in cattle such asbovine spongiform encephalopathy (BSE) aka ‘mad cow disease’.

4. Potential applications of NMR/MRI for inspection ofmicrobiological, physical and chemical quality of foods

NMR/MRI has been used to monitor food quality in a variety ofstudies that assess microbiological, physical, and chemical propertiesin different foods (Gostan, Moreau, Juteau, Guichard, & Delsuc, 2004;Gudjónsdóttir, Jónsson, Bergsson, Arason, & Rustad, 2011; Pykett,2000; Zehl et al., 2011).

MRI has been intensively used to inspect the microbiologicalquality of fruits and vegetables (Pykett, 2000) as well as meats(Gudjónsdóttir et al., 2011). Traditionally, control of microbiologicalquality in food relies on microbiological testing of representativesamples at various stages of production and/or of the final products.Such approaches only provide a certain degree of assurance of foodsafety and quality, as these methods use representative samplesthat depend on the distribution of microorganisms in samples,whereas MRI provides full real time image of microorganisms infoods. MRI was able to rapidly distinguish cucumbers with fungus(Mycosphaerella sp.) infection from healthy cucumbers (Hall, Evans,& Nott, 1998). NMR was also capable of monitoring fish deteriorationbased on correlation between NMR parameters with total viablecounts (TVC) of H2S-producing bacteria (Gudjónsdóttir et al., 2011).

Physical properties such as texture are considered one of the maineconomically important quality indicators in foods (Bourne, 2002) forboth consumers and producers. NMR techniques, especially MRI, havethe potential for detecting various quality factors related textures ordefects in fruits, and vegetables (Chen, Mccarthy, & Kauten, 1989; Hallet al., 1998). Scientists indicate a correlation between MRI imagechanges and textural changes of certain fruits, and vegetables under dif-ferent conditions (harvest, postharvest, storage). When a defect or anabnormal condition occurs, it is observed quite clearly in the MRIimage. Based on this observation, MRI revealed textural changes of sev-eral fruits such as melons, peaches, and pineapples during bruising andripening (Hall et al., 1998). Specifically, gradient-echoMRI images wereused to differentiate between healthy yellowmelons frommelons withinternal necrosis. Spin-echo MRI distinguished healthy peaches frombruised peaches. Multi-echo MRI image also identified unripe pineap-ples from the ripe. Similarly, Chen et al. (1989) showed the feasibilityof NMR imaging to detect the textural changes of fruits and vegetablesunder various conditions such as dry regions, bruising, worm damage,stage of maturity, and presence of voids, seeds, and pits via displaychanges in intensities of the images (Chen et al., 1989). Butz et al.(2005) also reviewed the use of NMR/MRI to measure water statesand water-related properties of fruits, including apples, pears, peaches,kiwi fruits and oranges (Butz et al., 2005). This review gathers ample ev-idence of the applications of NMR/MRI for assessing or inspecting qual-ity parameters of a variety of fruits, such as ripeness, defects, and decay,as well as differentiating between unaffected tissue, brown tissue, andcavities during various conditions, such as postharvest, storage, andtransportations (Butz et al., 2005).

In addition to its ability to assess physical properties of certainfoods, NMR/MRI can also be used to investigate chemical attributesrelated to product quality. For instance, NMR is used to investigatethe diffusion of two aroma compounds, ethyl butanoate and linalool,in matrices of carrageenan at low concentration (1%) and in some dif-ferent gelling states (Gostan et al., 2004). The results of these studiesfurther help to explain the impacts of structural and textural changeson aroma and taste perception of foods.

A recent study by Zehl et al. (2011) demonstrated the potential ofNMR with regard to quality control of medicinal herbal products (Zehlet al., 2011) by monitoring their unique bioactive compounds. Re-searchers highlighted for the first time that LC-NMR and off-line NMRanalysis are capable of identifying flavonoids and ellagic acid deriva-tives (Drosera rotundifolia and D. anglica, 2′-O-galloylhyperoside, withmyricetin-3-O-β-glucopyranoside and kaempferol-3-O-(2″-O-galloyl)-β-galactopyranoside in four Drosera species (D. anglica, D. intermedia,D. madagascariensis, and D. rotundifolia), which are traditionally usedfor the treatment of respiratory tract diseases. Due to the successfullyobtained results of qualitative and quantitative investigation of flavo-noids and ellagic acid derivatives, Zehl et al. (2011) highly appreciatedNMR identification which boasts of simple sample preparation, lowcost, and simplicity of analysis system. They further provide a recom-mendation of NMR technique as it is well suited for quality control ofherbal medicinal products.

In a recent review, quantitative water analysis by NMR (MRI) alsobecame a tool to measure meat quality (Pearce et al., 2011). The topicscovered in this review included water distribution and mobility, waterholding capacity as they relate tomeat quality, such asmuscle structure,juiciness and tenderness of meat. In other studies, the applications ofNMR have been expanded to investigate a variety of factors influencingmeat quality related to water, including animal growth rate and age,slaughter procedure, pre-slaughter stress, cooling rate of carcasses,aging, and storage temperature on the final meat products (Honikel,2004; Honikel, Kim, Hamm, & Roncales, 1986; Ruiz-Cabrera, Foucat,Bonny, Renou, & Daudin, 2005). All these studies amply displayed thepotential of NMR methodology for quantifying overall organolepticproperties of meat as well as providing information on how to optimizeprocessing conditions to obtain desired organoleptic properties.


Similar approaches have been applied to study the impact of differ-ent moisture levels (12%–45%) on the relaxation properties of wheatflour dough, which in turn becomes a good indicator of the elastic prop-erties of dough (Ruan et al., 1999; Yi & Kerr, 2009). It should be notedthat elastic properties can be measured directly using Magnetic Reso-nance Elastography (MRE) (Gruwel, Latta, Matwiy, & Tomanek, 2010).MRE is a phase-contrast MRI technique, which is used to map spatialdisplacement patterns corresponding to harmonic shear waves initiat-ed by the mechanical oscillations of a specially designed actuatorattached to the object (Gruwel et al., 2010). MRE has been used to de-termine shear stress in pre-packaged fruit puddings (Gruwel et al.,2010).

Frias, Foucat, Bimbenet, and Bonazzi (2002) also used NMR/MRI toexamine drying profiles of rice during processing, whereas, Castell-Palou et al. (2011) established NMR methodology on how to profilethe drying of cheese as function of temperature and air rates. All this in-formation obtained from NMR/MRI has lead to the optimal processingof these particular products (Castell-Palou et al., 2011; Frias et al.,2002). Successful examples of usage of NMR techniques to optimizefish processing for quality improvements have been covered in a recentreview (Erikson, Standal, Aursand, Veliyulin, & Aursand, 2012).

NMR spectroscopy combined with statistical analysis techniques isone of the promising tools for food quality control. One of such com-binations is SGF profiling with NMR, which is fully automaticallyperformed sample transfer, measurement, data analysis and reportingfor quality control of fruit juices (Spraul et al., 2009). Having establisheda spectral database (>6000 reference juice including 1500 fully authen-tic samples, taken by SGF inspector), NMR allowed identification andqualification of 28 different compounds in a mixture simultaneously(Spraul et al., 2009). In fact, it also enabled the detection of fraudulentaddition of sugar, citric acid, lemon juice (e.g., apple juice), orgalacturonic acid (in indicator of exhaustive enzymatic treatment).This technique was also capable of distinguishing the extraction ofjuice from different parts (i.e. peels) and origins of fruit, as well as rip-ened or unripened fruits (Spraul et al., 2009).

5. Application of NMR in food packaging

The quality of the packaged food is also directly related to the char-acteristics of the packaging with the proper selection and optimizing ofpackaging providing better maintenance, storage and handling of foods.NMR holds the promise to be able to investigate packaging materialproperties and optimize food packaging materials. In one study,the effects of gamma irradiation (at a range of 1–100 kGy) on food pack-aging polymers (polystyrene, poly-butadiene, styrene–acrylonitrile,high impact polystyrene and acrylonitrile–butadiene–styrene) weredetermined by NMR (Pentimalli et al., 2000). Researchers found thatpolystyrene is an ideal polymer for packaging food thatmay undergo ir-radiation. In another study by Lamanna, Piscioneri, Romanelli, andSharma (2008), 1H NMR was used to monitor degradation of Robiolacheese in air (without package) and in a composite paper foil packageduring a 7 day period at room temperature (15 °C). The spectrum ofthe cheese aqueous extract showedmore variation in the concentrationof certain chemical compounds occurring in the cheese exposed to airduring the 7 day storage period, compared with those of cheeses storedin the package (Lamanna et al., 2008). All these findings proved NMR'sability to evaluate the performances of various kinds of packages withrespect to its ability to preserve food in different storage conditions, inaddition to it being a promising tool for selecting desired food packagematerials.

6. Potential application of NMR/MRI in food authentication

Food authentication is one of the major concerns in regard to foodquality. NMR/MRI techniques applied to detect authentication withindifferent foods has been reported extensively. (Bertelli et al., 2010;

Cuny et al., 2008; Ellis et al., 2012; Masoum et al., 2007; Rinke et al.,2007; Schievano, Peggion, & Mammi, 2010). The potential use ofNMR in food authentication has been applied to several foods andbeverages, such as milk and cheese (Brescia, Monfreda, Buccolieri, &Carrino, 2005), beef (Shintu, Caldarelli, & Franke, 2007), truffles(Mannina, Cristinzio, Sobolev, Ragni, & Segre, 2004), vanillin(Tenailleau, Lancelin, Robins, & Akoka, 2004), pistachios (Zur, Heier,Blaas, & Fauhl-Hassek, 2008), and saffron extracts (Yilmaz, Nyberg,Mølgaard, Asili, & Jaroszewski, 2010). The scope of NMR in food au-thentication will be extended as the instrumentation decreases inprice and becomes more widely accessible allowing more regulatoryagencies around the world to opt-in for using NMR as the analyticaltesting method of choice for their samples while allowing the sampleto remain intact if it should be required during legal prosecution orany other reasons. Some representative foods cited in the followingsection include honey, salmon, olive oil, tea and beer.

6.1. Honey

The use of NMR in honey authentication dates back to one of the ear-liest studies, in which citrus honey was investigated by deuteriumNMR (Lindner, Bermann, & Gamarnik, 1996). In 2007, site-specific nat-ural isotopic fractionation measured by nuclear magnetic resonance(SNIF-NMR)was used to investigate honey authentication. Theories be-hind SNIF-NMR have been well documented (Martin, Akoka, & Martin,2006). Specifically in the study of Cotte et al. (2007), SNIF-NMR enabledthe determination of (D/H) ratio in the three isotopomers of ethanol:CH2DCH2OH (I), CH3CHDOH (II) andCH3CH2OD (III). The isotope exam-ined in this study of honey is deuterium and the isotopic ratio is mea-sured in the ethanol obtained by fermenting honey sugars. The (D/H)IIand (D/H)III ratios were correlated with the climatic conditions of thebotanical species and the nature of water in the samples, while the(D/H)I ratio was related to photosynthetic sugar metabolism (Cotte etal., 2007). Analyzing (D/H)I ratios provide specific values for certain or-igins (Cotte et al., 2007).

In recent years, limited production of honey caused a rise in honeyprices, and in turn, a rise in honey adulteration by producers throughthe addition of different commercial sugar syrups. Lolli, Bertelli,Plessi, Sabatini, and Restani (2008) initially conducted a study using2D HR-NMR which allowed for the determination of the botanical or-igin of unifloral honey, obtaining both efficient and versatile results(Lolli et al., 2008). Later, 1D NMR proved to be a more effective, sim-pler, and faster technique than 2D NMR in detecting adulteration inhoney without using any sample pre-treatments, yielding resultsthat were comparable to those obtained using FTIR with a 92.5% cor-rect prediction rate (Bertelli et al., 2010). Schievano et al. (2010) used1H NMR to identify the botanical origin of unifloral and polyfloralhoney, with minimal preparation, yielding 100% correct sampleidentification.

6.2. Salmon

Farmed salmon practice has grown dramatically from 6% to 58%during 1985 to 2000, this increase in farmed salmon is attributed toits lower price and higher omega−3 FA content compared to thewild variety. Farmed salmon, however, poses a risk of much higherconcentrations of organocholorine compounds (polychlorinated bi-phenyl (PCBs), dioxans) and chlorinated pesticides (toxaphene anddieldrin, along with other contaminants (Hites, Foran, Carpenter, etal., 2004; Hites, Foran, Schwager, et al., 2004). Due to preference,price, and the risk involved with farmed salmon, mislabeling thetype of salmon as well as the origin is a common occurrence insome fish markets. 1H NMR with support of data processing usingsupport vector machine (SVMs) was capable of distinguishing be-tween wild and farmed salmon including their origins with a high ac-curacy based on their muscle lipid profiles (Masoum et al., 2007). The


previous technique was furthermore refined by the use of 13C NMR tolook at the lipids extracted from the muscle. 13C NMR spectra have alarger chemical shift scale than the 1H NMR spectra yielding a betterobservation of the peaks and eliminating any overlaps (Aursand et al.,2009).

6.3. Olive oil

Virgin olive oils (VOOs) have been produced for thousands ofyears in countries around the Mediterranean Sea, with their qualitybeing linked to their geographical origin as well as processingmethods. The European Union (EU) has very strict rules associatedwith the labeling, of VOOs in terms of the specific production regionand production method. Due to the high market prices of VOOs, thefraudulent act of mislabeling the origin of VOOs, and the adulterationof the VOOs occur very often. Although several analytical methods al-ready exist for the detection of VOO adulteration, NMR fingerprintingwas proven to be amuchmore effectivemethod in the authentication ofVOOs based on their geographical origin (Alonso-Salces, Moreno-Rojas,et al., 2010). For authentication purpose, several variables have beenstudied, including 1H, 13C, and/or 31P NMR analyses, unsaponifiablefraction of VOOs and phenolic compounds in the polar fraction ofVOOs (Alonso-Salces, Holland, et al., 2010; Christophoridou, Dais,Tseng, & Spraul, 2005).

6.4. Beverages

The use of NMR for food authentication also extends to beveragesas well. 1H NMR spectroscopy showed potential in the discriminationof green tea according to the country of origin or with respect to qual-ity (Le Gall, Colquhoun, & Defernez, 2004). 1H NMRwas able to detectsimultaneously the catechins, the amino, organic, phenolic, and fattyacids, and the sugars from a single green tea extract. It was also capa-ble of detecting catechins, caffeine, 5-galloyl quinic acid, and 2-O-(â-L-arabinopyranosyl)-myo-inositol, all of which are associated totea quality (Le Gall et al., 2004). Another application field for NMRspectroscopy is to examine the source of the raw material used formaking juices. 1H NMR has also been shown to be very accurate inthe determination of the origin or quality of juices (Cuny et al.,2008; Rinke et al., 2007).

NMR spectroscopy is also widely used in alcoholic beverages forauthentication purposes, as these beverages command higher pricesin the market place. Unfortunately, as with VOOs, this increases therisk of fraud by adulteration and deliberate mislabeling. Zivania, a tra-ditional Cypriot alcoholic beverage was tested with 1H NMR spectros-copy to determine the country of origin for authenticity purposes(Petrakis et al., 2005). The results obtained were slightly less accuratethan traditional methods but they were still deemed to be acceptable.

Beer, the third most popular drink in the world after water and tea(Nelson, 2005) is enjoyed and consumed in many cultures. Due to thehigh prices commanded by some beers, adulteration practices includ-ing mislabeling of the place of origin unfortunately also exist with thispopular alcoholic beverage. Initially beer was characterized chemical-ly by high resolution 1H NMR observing many distinct chemicalsbetween different beers as well as the potential of NMR (Duarte etal., 2002). Further experimentation explored the potential NMR spec-troscopy for quality control of beer (Duarte et al., 2004). The samegroup explored the potential of NMR spectroscopy to observe thecomposition of beer and relate it to the brewing site and date of produc-tion, showing the potential to use PCA/NMR to monitor and control thebeer production process (Almeida et al., 2006). The quality control ofbeer was explored a year earlier (Lachenmeier et al., 2005) with theresults obtained suggesting that NMR could be used for quality controland authentication of beer.

7. Potential applications of NMR/MRI for on-line monitoring offood processing

The use of traditional analytical methods for on-line process mon-itoring and process optimization is challenging, as these methods aretime consuming and sample-destructive. Numerous non-destructivemethods have been used to evaluate the quality of foods includinglight transmission, X-ray transmission, sonication and vibration.However, these approaches failed to provide information about mul-tiple (or complex) physical properties of some foodstuffs (Chen et al.,1989). The use of NMR/MRI for online monitoring of the process isone such promising alternative. NMR/MRI has been initially success-fully developed for online analysis of bio-processes in life science,this is due to its capability of shortening the time delay for offlinesample preparation and analyses (Kara, Mueller, & Liese, 2011). Re-cently, food scientists have also successfully extended the scope ofsuch usage to food on-line processes.

Gudjónsdóttir and his co-researchers, demonstrated the possibilityof using a low-field proton nuclear magnetic resonance (LF-NMR) ana-lyzer (at a frequency of 20 MHz) for on-line process control during pro-cessing of cold water shrimp (Pandalus borealis). Specifically, theyattempted to determine the impact of polyphosphate concentrationsand length of pre-brining and freezing on physicochemical propertiesof shrimp muscles. Prior to cooking the shrimp at 80 °C for 15 s, threespecific stepswere performed. LF-NMRwas capable of rapidly detectingphysicochemical property changes in shrimpmuscle after each of thesethree treatments. The changes include protein content, phosphatelevels, and moisture content as well as water-holding capacity (WHC).They also pointed out that further optimization is necessary in regardto measurement settings, number of sample replicates, the size of ana-lyzing surface as well as suitable probe selection. The same researchgroup also confirmed that LF-NMR can differentiate wild farmed codfrom farmed cod processed pre-rigor and post-rigor in terms of themuscular structure and physical properties (Gudjonsdottir et al.,2010). They highly recommended that LF-NMR can be considered avaluable on-line control tool to optimize the salting and sorting processof these types of cods that are slightly salted.

In addition, the use of an LF-MRI (5.55 MHz) sensor and conveyorsystem for online determination of the internal browning in wholeapples was reported by Chayaprasert and Stroshine (2005). Suchnon-destructive detection of internal defects makes it possible todistinguish healthy apples and apples with internal browning, andexpand the capability of currently available on-line quality sorting,which are typically used on to monitor external properties such ascolor, size, shape, or externally visible defects (Chayaprasert &Stroshine, 2005). Another researcher has also tried to employ a Maranbench top NMR spectrometer (15 MHz) for on-line determination ofthe gelatinization temperatures of corn starch, when combined withother food components, like sugar (i.e. glucose and sucrose) and variousgums (i.e., xanthan) (Gonera & Cornillon, 2002). This allowed for themonitoring of changes occurring in starchy foods on the addition ofother ingredients. NMR-spectroscopy also has potential for the analysisand determination of fine structures in carrageenan. Quantitative anal-ysis of carrageenan is important for ingredient suppliers and foodman-ufacturers. Specific applications of such analysis range from screeningtools and quality control to studying the processing parameters andstructural components. This approach helps understand the possiblecommercial or industrial value of raw extracts obtained from redseaweeds as well as the influence of processing parameters such astemperature and pHon the structure, which ultimately allows suppliersto develop and deliver a consistent consumer product (van de Velde,Knutsen, Usov, Rollema, & Cerezo, 2002). In a review by van de Veldeet al. (2002), both 1H NMR and 13C NMRwere documented in detail re-garding their potentials of qualitative and quantitative analysis of carra-geenan samples. 13C-NMRspectroscopy can be used for distinguishingthe polysaccharides of the agar and carrageenan groups. Since the pairs


of dyads G–D and G–L, as well as G–DA and G–LA, are diastereoisomericand give different spectra, such differences were noticeable for theanomeric carbon resonances. Quantification of different carrageenan ori-gins in a sample by 1H-NMR is based on the resonances of the a-anomericprotons in certain regions (van de Velde et al., 2002).

Another possible use of NMR is to resolve the diffusivity of aromacompounds within various food matrixes (Gostan et al., 2004;Juteau-Vigier et al., 2007; Savary, Moreau, & Cayot, 2010). Gostan etal. (2004) evaluated the effectiveness of NMR Diffusion Ordered Spec-troscopy (DOSY) investigating self-diffusion of small aroma solutes(ethyl butanoate and linalool) in natural polysaccharide polymers(iota-carrageenan matrix), thickeners in the food industry (Gostan etal., 2004). This approach worked well for estimating the diffusion andpartition properties of another aroma compound (ethyl hexanoate) incarrageenan matrices (Juteau-Vigier et al., 2007). Savary et al. (2010)formulated eight polysaccharide composite gels composed of sucrose(35%, w/w), starch (1.4%, w/w), carrageenan (0.05% (w/w), 0.33%(w/w), 0.80% (w/w)) with (Ci) or with pectin (P) at 0.40% (w/w)using different salts (K+, Na+ and/or Ca2+). These gels can be used toflavor commercial dairy products and can cause them to impart differ-ent textural properties. 1H pulsed-field gradient (PFG) NMR spectrasuccessfully recorded the diffusion of ethyl butyrate in all eight texturedgels (Savary et al., 2010). All these above experimental trials promote abetter understanding of the performance of aroma food deliverysystems, therefore leading the development of new food products.

8. Specific NMR/MRI applications to some representative foods

8.1. Wine and beer

Due to the fact that water, ethanol, and acetic acid comprise themajor proton containing components in the full bottle of spoiled wine,therefore measurement of the intensity of their peaks in the 1H NMRspectrum should able to determine the degree of wine spoilage(Weekley et al., 2003). Several researchers studied spoilage propertiesof bottled wines by measuring the acetic acid content down to thelevel of complex sugars, phenols, and trace elements in wine (Lopez-Rituerto et al., 2009; Sobieski et al., 2006; Weekley et al., 2003).

Currently, there are cases in which dissolved cocaine has beensmuggled illegally with the aid of wine bottles. Gambarota et al.(2011) have tackled this issue by detecting dissolved cocaine reso-nances in intact wine bottles. This was accomplished through a stan-dard clinical MR scanner, within a scan time of 1 min detectable atlevels of 5 mM (i.e. ~1.5 g/L). This technique can examine suspiciouscargo since it allowed non-destructive and rapid content characteri-zation (Gambarota et al., 2011). These studies emphasize the utiliza-tion of a full bottle NMR approach, being applicable to any type ofwine (Sobieski et al., 2006; Weekley et al., 2003).

This area of research extends to other alcoholic beverages as well(Table 2). The synergetic combination of 1H NMR with FTIR-attenuated total reflectance (ATR) can separate different beers basedon alcoholic content (Duarte et al., 2004). This provided rapid informa-tion regarding different types of beer fermentation, a crucial aspect inbeer production. Rodrigues et al. (2010) identified six useful organicacids; acetic, citric, lactic, malic, pyruvic, and succinic acids. Organicacids play an important role in beer, not only contributing to flavor,color, and aroma but they also are good indicators of fermentation per-formance. This established PLS-NMR method for organic acid quantifi-cation in beer, provides important information on the product'squality and history (Rodrigues et al., 2010).

8.2. Fruit and vegetable juice and pulp, green tea, and coffee

In addition towine and beer, research on other beverages such as to-mato juice with pulp, green tea, and coffee can also benefit from NMRand MRI technology. Methods comprising 1H HR-MAS NMR have

determined the chemical composition of tomato juices and total pulpfrom two tomato cultivars, i.e. Red Setter and Ciliegino (Sobolev et al.,2003) including a variety of aliphatic groups in amino acids and organicacids. The fluid section was measured with standard HR NMR andtomato pulps were analyzed by magic angle spinning (MAS) NMR. Inparticular, valine, isoleucine, threonine, alanine, glutamate, glutamine,aminobutyrate (4-aminobutanoate), asparagine, aspartate, citrate (2-hydroxypropane-1,2,3-tricarboxylate), acetate and malate were identi-fied. The comparison between the juice and pulp spectra reveals all thewater-soluble substances that are present in the pulp extracted fromthe juice. 1H HR-MAS NMR has advantages, allowing the study ofsemi-liquid or semi-solid samples without extraction (mostly food)and obtaining a spectral resolution as if the sample were liquid.

Coffee is a popular beverage containing the stimulant caffeine; theworlds' most widely consumed psychoactive substance. Many major orminor compounds in coffee have aroused scientific interest, including caf-feine, formic acid, trigonelline and 5-hydroxymethylfurfural (5-HMF).Among these compounds, caffeine and trigonelline are associatedwith bitter taste, formic acid determines the level of acidity of coffeeand hydroxymethylfurfural (5-HMF) serves as an indicator of qualitydeterioration during coffee roasting.

Signal assignment of many major constituents present in coffee(i.e. caffeine, formic acid and trigonelline) has been performed using1H NMR techniques. The sensitivity and precision of NMR for quantita-tively determining some major or minor compounds in coffee havebeen described in a recent study (del Campo et al., 2010). Specifically,1H NMR was used to quantitate the content of caffeine, formic acid,trigonelline, and 5-hydroxymethylfurfural (5-HMF) in their commer-cial soluble coffees at 30 °C. 1H NMR spectra of these coffees revealthat they contain 4.2% caffeine, 2.6% formic acid, 2.4% for trigonelline,and 7.3% for 5-HMF. Since previous studies only established the qualita-tive analysis of caffeine, formic acid, and trigonelline by 1HNMR (Bosco,Toffanin, De Palo, Zatti, & Segre, 1999). This study was considered thefirst to report the quantitative procedures of the NMR technique forchemical analysis of coffee (del Campo et al., 2010).

One study established a quantitative NMRmethodology for formicacid determination in apple juice (Berregi, del Campo, Caracena, &Miranda, 2007). Five varieties of Spanish Basque cider apples were se-lected in this study, including Moko, Patzuloa, Txalaka, Urtebi Haundiand Urtebi Txiki. The researchers optimized the 1H NMR acquisitionconditions to ensure that the signal for formic acid appears at8.2–8.4 ppm without overlapping with signals of other chemicals.They also successfully validated their technique by an enzymaticmethod, in which formic acid is quantitatively oxidized to bicarbon-ate by nicotinamide–adenine dinucleotide (NAD+) in the presenceof enzyme formate dehydrogenase (FDH). The amount of formicacid was determined by measuring the absorbance of NADH at340 nm to determine formic acids (Berregi et al., 2007).

Quality predictions for green tea are often performed by highlytrained tea tasters using a sensory testing. This process, however,can be rather inconsistent as it is somewhat subjective leadingTarachiwin et al. (2007) to introduce new methods involving meta-bolic profiling and finger printing using 1H NMR. In this study, driedground green tea leaves were mixed with D2O, incubated at 60 °C,centrifuged to separate the supernatant containing the hydrophilicmetabolites, which was then filtered and mixed with a buffer beforetesting. Subsequently, 1H NMR was able to identify the levels of chem-ical constituents in Japanese green tea in different frequency regions.More specifically, theanine (δ 1.10, 2.12, 2.39, 3.19 ppm) and quinicacid (δ 1.88, 1.97, 2.05 ppm) at δ 0.5–3.0 ppm, whereas caffeine(δ 3.27, 3.43, 3.89 ppm), arginine (δ 3.22, 3.47 ppm), myo-inositol(δ 3.30 ppm), chlorogenic acid (δ 3.89, 4.22 ppm), and quinic acid(δ 3.56 and 4.01 ppm)were observed at δ 3.0–4.5 ppm, after excludingsucrose and fructose signals, 2-O-β-L-arabinopyranosyl-myo-inositol(δ 5.19 ppm), p-coumaryl quinic acid and/or cinnamic acid (δ 7.51,7.75 ppm), EGCG (δ 6.61, 7.02, 7.14 ppm), and ECG (δ 6.91, 7.02 ppm)

Table 2Specific NMR/MRI applications to some representative foods.

Foods Sample information Research objective Type NMR Observations Reference

Wine Entire bottle-unopened Rioja redwine

To monitor the levels of importantmetabolites of wine during thealcoholic and malolacticfermentation processes

1H qNMR Quantitative nuclear magnetic resonance allowed simultaneous detection ofethanol, acetic, malic, lactic, and succinic acids, and the amino acids prolineand alanine, besides the ratio proline/arginine through grape fermentationcorresponding to the Tempranillo variety.

Lopez-Rituerto et al. (2009)

Entered bottle To estimate spoilage 1H NMR 1H NMR with optimized 1331 water suppression pulse sequencedetected ppm ethyl alcohol and 2.1 ppm oxidation products (acetic acid oracetaldehyde) in full bottles of wine.Oxidative change of a bottle of wine can be detected within 10 min

Sobieski, Mulvihill, Broz, andAugustine (2006)

Entire bottles of UC DavisCabernet Sauvignon (1950–1977)

To measure spoilage indicators(such as acetic acid).To detect complex sugars, phenols,and trace elements in full intactwine bottles

1H NMR and selectedbottles with 13C NMR

Lack of correlation was observed between acetic acid concentrations and wineage. The sensitivity of the acetic acid measurement is less than 0.1 g/LThe integrity of the cork and hence the quality of the bottle seal against oxygenleakage with time was found to be important factors to prevent acetic acidcontaminationEthanol concentration does not correlate well with year and varies between 10and 20%

Weekley, Bruins, Sisto, andAugustine (2003)

Entire bottles wine+phantoms ofwine+cocaine, or water+cocaine

To detect cocaine dissolved in winesusing a non-invasive and non de-structive method

Water suppressed 1H MRSusing a 3 T clinical scanner

Peaks of 3 main groups in the cocaine molecule (aliphatic ring, methyl, andaromatic proton) are observed

Gambarota et al. (2011)

Beer To determine the spectralparameters

FTIR-ATR and 1H NMR The separation of beers mainly according to their alcoholic content; twogroups characterized by the predominance of dextrin, one group ofalcohol-free beers characterized by the predominance of maltose, and onegroup where glucose were found to predominate

Duarte, Barros, Almeida, Spraul, andGil (2004)

10 ml beer sample dissolved insolution

To quantify the major organic acidsin beer, acetic, citric, lactic, malic,pyruvic and succinic acidsTo determine properties of beer andfermentation performance.

Partial least squares(PLS)-NMR spectroscopy1H NMR — neosypr1d pulsesequence (Bruker library)

PLS1-NMR proved to be an effective rapid method for analyzing the majororganic compounds in beerOut of the 6 compounds measured, compared to other analytical methods,malic and pyruvic acid was slightly overestimated, and there was apparentoverestimation for citric acid

Rodrigues et al. (2010)

Tomato Juiceand Pulp

Puree for pulp analysisPuree extracts containing 30% D2O,with DSS (3-trimethylsilyl-1-propanesulfonic acid, sodiumsalt), placed in a 5 mm NMR tubeTwo tomato cultivars, Red Setter andCiliegino

To obtain high resolution protonspectrum of tomato pulps andtomato juices.To identify, quantify, analyze andcompare the results between tomatopulps and juices.

1H High Resolution Magicangle spinning(HR-MAS)NMRfor tomato pulpsHigh-resolution inverse probe.Liquid state NMR for tomato juice

Detailed assignment of HR NMR spectra of Red Setter tomato juice wasobtained :

− In the high-field region of the proton spectrum, the resonances aremostly due to aliphatic groups of amino acids and organic acids ofthe tricarboxylic acid metabolic cycle.

− In the middle field region (from 3.2 to 5.3 ppm), the resonances aremostly due to saccharides and major components (D-glucose andD-fructose)

− In the low-field region (from 5.5 to resonances are mostly due tominor components of tomato juice such as aromatic amino acids,phenolic compounds and formateAll water-soluble substances present in both pulp and juice.Both liquid state NMR and HR-MAS NMR produced consistent re-sults, except HR-MAS NMR was also able to detect insoluble sub-stances such as lipids

Sobolev, Segre, and Lamanna (2003)

Green tea 53 Japanese dried first-crop greentea leaves or Ichiban cha600 μL solution contain 200 μL of0.2 M buffer solution containing3 mM DSS and 400 μL D2O water teaextract

To produce a Japanese green teaquality prediction method usingmetabolic profiling and fingerprinting of 1H NMR spectra.Allowing for consistent and accuratejudging between different teaqualities.

Non-targeted 1H NMR basedmetabolomics.Presaturation pulse sequence usedto suppress the residual water signal

Information on the quality evaluation of Japanese green tea was provided via1H NMRNMR offered higher reliability in results over the traditional method oftesting Japanese green tea quality. specifically to quantitative and qualitativeevaluate sensory quality of green tea is derived from the metabolites(e.g. caffeine, theanine, EGCG, ECG, EGC, and EC) in the matter of easiersample preparation and quicker resultsThe PLS regression model of green tea have correlation coefficient R2 (good-ness to fit): 0.987, correlation coefficient Q2 (goodness of prediction): 0.671,root mean squared error of estimation (rmsEE): 1.82, and root mean squarederror of prediction (rmsEP): 9.22

Tarachiwin, Ute, Kobayashi, andFukusaki (2007)

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Sampleinformation

Research objective Type NMR Observations Reference

Tea sample dissolved and placed in5 mm NMR tubeFresh green tea leaves fromHannam, Dosun and Seogwang areasin South Korea

To investigate the effects of climateconditions on green tea metabolites

1H NMR 500 MHz, NOESTPRESATpulse to suppress water signal.

differences were observed in the OPLS-DA score plots derived from the 1HNMR green tea spectra between the Hannam and Dosun areas, between theDosun and Seogwang areas, and between the Hannam and Seogwang areas(Pb0.05)Green tea metabolome have been found to be d influenced by climatic con-ditions (sun exposure time, precipitation, and temperature) in different area

Lee et al. (2010)

Coffee Commercial soluble coffees include:Baque Natural Eroski Tueste Natural,Fortaleza Natural Marcilla CremeExpress Natural, Nescafe Alta Rica,Nescafe Classic Natural, NescafeExpresso, Nescafe Solo and SparTueste Natural600 μL placed in a 5 mm outerdiameter NMR tube

To quantify caffeine, formic acid,trigonelline and 5 (hydroxymethyl)furfural (5-HMF) in soluble coffees

500 MHz 1H NMR Solvent suppres-sion using the Watergate pulsesequence

For 10 measurements by 1H NMR, the coefficients of variation obtained are4.2%, 2.6%, 2.4% and 7.3% for caffeine, formic acid, trigonelline and 5-HMF,respectively, throughout 5 daysResults from 1H NMR are in good agreement (P>0.05) with those from thereference methods (HPLC standard method determines caffeine, trigonellineand 5-HMF and commercial enzymatic method determines formic acid)

del Campo, Berregi, Caracena, andZuriarrain (2010)

Edible Oils 200 μL directly transferred to 5 mmNMR tubeEdible vegetable oils include soybean(6), canola (3), sunflower (5), corn(5), rice (2), and olive (8)

To develop an effective, simplemethod of analyzing fatty acidcontents in edible oils and comparethe method to official AOAC methodof gas chromatography

1H NMR Using 1H NMR provided similar results to gas chromatography results (atsignificance levels higher than 95%). However, unlike CG, 1H NMR proved tobe a rapid, simple, robust and sensitive.There was no need for sample pre-treatment such as extraction, allowing 1HNMR technique to be environmentally and economically friendly

Barison et al. (2010)

Olive oil sample in (20 μL) dissolvedin solution and placed into 5 mmNMR tubeOlive oil from the Adriatic district in theMolise region (southern central Italy)

To investigate the influence ofharvest period and method on thecomposition of olive oil

1H NMR Volatile compounds (hexanal, trans-2-hexenal, sn-1,3-diglycerides, andsqualene) significantly. decreased in concentration significantly during theripening period (Pb0.05)ΔK parameter and the amount of hexanal were much higher in olives thatwere obtained via a shaker, whereas olives that were obtained using a combhad lower levels

D'Imperio et al. (2010)

963Virgin olive oils (VOOs) fromItaly (661), Spain (144),Greece (97),France (39), Turkey (14), Cyprus (6),and Syria (2)40 μL of each samples dissolved into200 μL deuterated chloroform —

placed in a 2 mm NMR capillary

To determine authentication ofvirgin olive oil by identification ofgeographical origin at the national,regional and or protecteddesignation of origin (PDO) level.

1H NMR Partial least-squares discriminant analysis (PLS-DA) model recognized 94% ofGreek, 81% of Italian, and 75% of Spanish oils in the training-test sets andpredicted correctly 88% of Greek oils and 69% of the samples from Italy andSpain in the cross-validation and 81% of Greek, 79% of Spanish, and 66% ofItalian oils in the external validationPLS-DA correctly classified Greek and non-Greek VOOs (>90%)δ13C of olive oils could discriminate Greece, Spain, and Italy VOOs (the meanvalue of δ13C follows a order of ItalianbGreekbSpanish oils)

Alonso-Salces et al. (2010)

Olive, hazelnut and sunflower oils To perform a composition analysis 1H NMR spectroscopy Separation between these three oils of different botanical origin andpermitted the detection of their mixtures

Fauhl, Reniero, and Guillou (2000)

Lettuce Water soluble extract and lipidicfraction extract were prepared andplaced into 5-mm NMR tube

To identify and assign in details the1H NMR spectra of lyophilizedlettuce

1D and 2D 1H, 13C and 31P-NMR A large number of water soluble metabolites were identified, as well asmetabolites extracted in organic solvents were identified as well.

Sobolev, Brosio, Gianferri, and Segre(2005)

Supernatant from processed mixtureinto 5 mm NMR tube

To compare the water solublemetabolites between wild typelettuce and GM modified lettuce anddetect any differences.

1D 1H NMR, 600.13 MHz2D NMR, 1H–1H TOCSY, and 1H–13CHSQC

NMR results on their own did not derive any information; however after properstatistical analysis. different levels of metabolites were correlated with the GMlettuce and wild type lettuce. The highest impact was noted in the trend of glu-cose and fructose content which was inverted when compared to the wild type.

Sobolev et al. (2010)

Onions 2-cm thick equatorial slice of yellowtype onion bulbs 5×5 mm piece intoNMR tube2 control treatments:(1) raw onion, 0.1 MPa, 20 °C;(2) raw onion, vacuum packed(0 MPa)2 treatments:(1) high pressure (20–200 MPa,5 min)(2) thermal treatment (40 to 90 °C,30 min)

To study the effects of high pressureand thermal processing onmembrane permeability andintegrity in plant tissue using 1HNMRTo verify that 1H NMR is a useful re-liable tool to measure changes in cellmembrane permeabilityTo determine the range of pressurethat would induce changes in oniontissue membrane permeability

1H NMRCarr–Purcell–Meiboom–Gill (CPMG)pulse sequence

1H NMR proved to be an effective method to quantify cell membrane damagein plant tissue. It was possible to distinguish between different degrees ofmembrane damage.This method will allow for the selection of the best food processing methodbased on the impact on tissue integrityThe greatest percent of weight loss was observed in the frozen sample withan average of 16.7% . The weight losses increased along with increase intemperature during thermal treatments. For all the high pressure treatmentsbelow 200 MPa, the percentage of weight loss was insignificant.

Gonzalez et al. (2010)

Freeze dried sample to exert water,prepared solution of 700 μL into5 mm NMR tubes

To investigate the extractedmetabolites in raw onions andaqueous onion solution using a fasteffective method. To compare the

300 MHz (7.05 T)1D, 2D 1H (COSY sequence) NMRspectroscopy

3 main saccharides. 17 amino acids and 5 organic acids were detected withthe use of NMR spectroscopy. The results were similar to other methods.Using NMR spectroscopy proved to be a simultaneous and direct detectionmethod.

Tardieu, De Man, and This (2010)

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Table 2 (continued)

Foods Sample information Research objective Type NMR Observations Reference

results from H NMR tohigh-performance liquid chroma-tography (HPLC), mass spectroscopy(MS, MS/MS), and thin layer chro-matography (TLC and PLC)

Sweet pepper 253 Italian sweet peppers (Capsicumannum L.)101 peppers belonged to cv. “Corno”152 peppers belonged to cv. “Cuneo”.25 mg fresh sweet pepper for 1D andfreeze dried for 2D NMR.

To produce a detailed chemicalcharacterization of sweet pepper,and identify major compounds bymeans 1D and 2D NMR using a freshsweet pepper samples withoutsample preparation.

400 MHz 1H and 13C NMRHRMAS-NMR (high resolution magicangle spinning nuclear magneticresonance) H

Using HRMAS-NMR, metabolic profile of sweet pepper was observed andrecorded.With PLS-DA analysis, the 1H NMR spectra reveals that the metabolites mainlycontributing to the discrimination between the two cultivars considered weresugars and organic and fatty acids.PLS-DA analysis allowed for the determination of geographical origin of thepepper sample: For cv. “Corno”. an acceptable discriminationwas obtainedwithan overall non-error rate of 92.1%; For cv. “Cuneo”, an acceptable discriminationwas obtained with an overall non-error rate of 94.7%

Ritota, Marini, Sequi, and Valentini(2010)

Potatoes Five potato varieties (Sava, Berber,Ditta, Bintjemedio-dry-matter andBintje-high-dry-matter) stored at4 °C and 95% relative humidity fortwo and eight months,For cooked potatoes, whole potatoeswere peeled and boiled in water for20–25 min

To predict sensory texture qualityattributes of cooked potatoes,including hardness, cohesiveness,adhesiveness, mealiness, graininessand moistness.To investigate the correlationbetween advanced image analysisfeatures determined in differentregions of raw potatoes, and sensorytexture attributes of cookedpotatoes.

NMR-imaging (MRI) Potentially, MRI data from raw potatoes could used to predict sensory attri-butes is related to the texture of cooked potatoes.Compared with the MRI features from horizontal and vertical regions, thehighest prediction was obtained by the MRI features from the full regionwithin the potato, For hardness, 76% of the variation was predicted; for ad-hesiveness 54% and for moistness 50% of the variance was predicted,resulting in correlation coefficients of 0.86, 0.72 and 0.69, respectively. Formealiness and graininess, the variances were below 55%. the vertical regionseemed to predict y better (46%) than both the full and the horizontal regionsThe MR-image features predicted 70% of the variation in hardness of thecooked potato.

Thybo et al. (2004)

Apples Slices To perform texture analysis duringripening and storage

MRI A significant correlation was found between acidity and texture analysisparameters such as sum average, sum variance and sum entropy.The dynamics of Texture analysis parameters during the periods ofmaturation and storage were described by polynomial functions

Létal et al. (2003)

Mango Mango fruits (“Tommy Atkins”cultivar)

To study the composition of mangoduring ripening using solid state andliquid state NMR in an intact mangopulp and mango juice respectively.Prove HR-MAS NMR to be a non de-structive analytical tool for fruitanalysis.

Water suppression and 2D NMRHR-MAS NMR using 400 MHz 1Hand 100 MHz 13C for the intactmango pulpNMR spectra for the juice samplewas produced using a 600 MHz 1HNMR

Main sugars (glucose, fructose and sucrose) and approximately 40 metabolitesand were identified in mango samples at different ripening stagesIn mango pulps, sucrose predominates over fructose and glucose at mostripening stagesCitric acid is the most abundant organic acid in the unripe mango, decreasingdramatically through the ripening process.

Gil et al. (2000)

Rice Rice To analyze the water distributionand structural changes

1H NMR Internal hollows were observed in all examined cooked rice grains, and wepropose a mechanism to explain their formation. The origin of these hollowswas hypothesized to be cracks or fissures, and hollows resulted from sealingof such lacerations by gelatinized starch in the peripheral layer incombination with expansion of the grain during cooking.

Horigane et al. (1999)

Cocoa beans Fermented cocoa beans (Forastero,Criollo, and Trinitario) from differentcountries (Ecuador, Ghana, Grenada,and Trinidad)Dried fermented cocoa beans extractsre-dissolved in 1 mL of D2O/CD3OD(8:2 v/v) containing 0.1% of TSPDiluted samples, 5 mm NMR sampletube

To quantitatively and qualitativelyanalyze the composition offermented cocoa beans and todistinguish between varieties andgeographical region

1H NMR spectra of hydroalcoholicextracts

1H NMR successfully quantified amino acids, polyalcohols, organic acids,sugars, methylxanthines, catechins, and phenols in different varieties ofcocoa beans1H NMR analysis could be used as a rapid method for cocoa bean qualitycontrol by quantifying methylxanthines and catechins.

Caligiani, Acquotti, Cirlini, and Palla(2010a)

Maize Processed seeds in solution placed instandard 5 mm NMR tubeDry samples were dissolved in a D2Ophosphate buffer (100 mM, pH7.2)containing trimethylsilylpropionate(TSP, 1 mM) as internal standard.

To compare metabolites of maizeseeds from the transgenic maizevariety 33P67 to the traditionalvariety.

600 MHz Bruker 1H NMR and 2D1H–1H and 1H–13C

The 1H spectra from both seed lines turned out to be identical, howevertransgenic extracts, higher levels of ethanol, citric acid, glycine–betaine,trehalose, and an unknown compound were observed that allow for adistinction between the two varieties (transgenic and nontransgenic seedmaize samples).Several compounds (ethanol, lactic acid, citric acid, lysine, arginine, glycine–

Piccioni, Capitani, Zolla, andMannina (2009)

Onions

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Sampleinformation

Research objective Type NMR Observations Reference

betaine, raffinose, trehalose, R-galactose, and adenine) were identified for thefirst time in maize with 1H NMRApproximate 40 water-soluble metabolites in the maize seed extracts wereidentified.

Whey proteingels

Whey protein isolate (WPI)containing 95.6% proteinWPI gels — in 8 slices. 6.2 mmthickness of each slice

To quantify changes in geometryand water content of whey proteingels and detect swelling wheyprotein gels in solutions at 3different pHs.

1.03 T NMR spectrometer —proton NMR-MRI images — T1 andT2 times

MRI can be used to monitor the rate and extent of how whey protein-basedgel swell at different aqueous environmentsAt pH 7 and 10, mass uptake of WPI gel correlated with volume change ofWPI gels (R2=0.99)

Oztop, Rosenberg, Rosenberg,McCarthy, and McCarthy (2010)

Soybean 2 g of strip sample of Chinese Soyprotein isolate (SPI) placed in15 mm NMR tube

To observe the state of water intexture soybean protein (TSP) andthe changes of water states anddistribution in TSP when extruded atdifferent feed moisture contents andcooking temperatures.

1H Using low field nuclear magneticresonance (LF-NMR) 22.6 MHz, usedCarr–Purcell–Meiboom–Gill (CPMG)sequence to measure spin–spinrelaxation time (t2)

The results from both methods were consistent. It was found that waterspreads in a homogenous manner, and the intensity of water distributionincreased as total water content increased.Freezable and non-freezable water content determined by differential scan-ning calorimeter (DSC) were correlated to the results of spin–spin relaxationtime constants T22 and T21 from NMR at the correlation coefficients were 0.96(pb0.01) and 0.54 (p b0.05), respectively.

Chen, Wei, and Zhang (2010)

Methanolic extract of defattedsoybean — solution in 5 mm NMRtube

To investigate fingerprint soybeanextracts, such as amino acids,carbohydrates, organic acids,emphasizing on isoflavonesquantification

1H NMR, 14.1 T, 600 MHz. Usedselective water signal irradiation

1H NMR analysis provided accurate results, with the advantages of minimalsample preparation, and rapid acquisition time of data.

Caligiani, Palla, Maietti, Cirlini, andBrandolini (2010)

Cheese Cheese made from pasteurizedcow's milkCheese placed in drying chamber at1, 3, 6, 9, 13 and 26 days of drying

To investigate determine moistureprofiles of cheese during drying

A time-domain nuclear magneticresonance (TD-NMR)

A proposed diffusion model satisfied both the drying curve (mean relativeerror (MRE)=0.4% and percentage of explained variance (%var)=99.7%)and the moisture profiles (average MRE=4.4% and %var=94.5%)The predicted moisture content (TD-NMR method) is correlated withvacuum oven methods (according to the International Dairy Federation (IDF,1982) standard norm 4A0 (r2=0.999)

Castell-Palou, Rossello, Femenia,Bon, and Simal (2011)

Beef 600 μL of supernatant transferredinto 5 mm NMR tube

To evaluate the metabolite profile ofbeef post mortem, and monitor thechanges occurring during the agingof beef

1H NMR, 300 MHz Aging of sample was shown to effect metabolites, specifically theconcentration of amino acids due to an increase in proteolysis.

Graham et al. (2010)

40 authentic raw beef samples fromAustralia, Korea, New Zealand, andthe United StatesPrepared liquefied sample — 5 mmNMR tube

To identify metabolites in raw beefthat will enable geographicallocation of the beef origin to beidentified

1H NMR, 600 MHz, NOESY-PRESATpulse sequence to suppress residualwater signal

1H NMR proved to be effective in identifying metabolites in aqueous raw beef,which helped to identify the geographical origin of beef.Succinate and various amino acids such as isoleucine, leucine, methionine,tyrosine, and valine could potentially be used as markers to distinguish be-tween various raw beef samples

Jung et al. (2010)

Fish 8–10 mg of white muscle sampleSmoked Atlantic salmon (S. salar)

To detect and identify the maincomponents in smoked salmon.To identify what changes may occurin the metabolite profile of smokedAtlantic salmon during storage

1H-HRMAS NMR spectroscopy.500.13 MHz (11.7 T)

1H-HRMAS spectra of smoked salmon shows the presence of FAs,triacylglycerides and phospholipids, carbohydrates, nucleoside derivatives,osmolytes, amino acids, dipeptides, various organic acids (acetic acid,succinic acid, lactic acid, fumaric acid and formic acid), pyrimidine derivativeuracil as well as ethanol (a fermentative degradation product of sugars).This method proved to be a rapid non-destructive technique to identifyvaluable information in foods. Estimation of DHA and other polyunsaturatedFAs by direct analysis was achieved without chemically preparing the sampleand extract lipids as usually required by other methods.

Castejón et al. (2010)

Samples minced and placed in10 mm sample tubes (Atlantic cod)

To detect physical and chemicaldifferences between wild andfarmed cod (pre and post rigor) interms of effect of brine injection,brining, and freezing

A low-field Brukermq 20 BenchtopNMR analyzer with 20 MHz protonfrequency

Muscle structure information for the farmed and wild cod as well as the stateof the water in the muscle during brine injection, brining and during rigortension was attained — NMR can be used to optimize the salting and storingprocess of wild and farmed cod

Gudjonsdottir et al. (2010)

15 mg sample (Arctic char, CentralSweden)

To obtain nutritional value of fish,such as PUFA composition and majorsmall metabolites in intact muscle ofarctic char

1H HR-MAS NMR spectroscopy600 MHz

n−3 FA, EPA and DHA in fish oil were determined using 1H HR-MAS NMRspectroscopy in intact muscles. provide fatty acid profile and major metabo-lites of fish without hydrophilic and lipophilic extraction

Nestor et al. (2010)

Manuka honey Diluted samples To accurately and rapidly measurethe levels of methylglyoxal inManuka honey.

11.7 T Bruker Avance III 500 MHzNMR (1H resonances with watersuppression

qNMR method worked for quantifying methylglyoxal in Manuka honeywithout chromatographic separation or a derivatization procedureResult also showed that other methods may have overestimated [MGO]

Donarski, Roberts, and Charlton(2010)

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were also observed. The x-axis of the spectrum is the delta scale(δ) with units of ppm and the y-axis is an intensity scale. Theseabove-mentioned compounds were targeted in this study becausethey are all relevant in regard to the quality of green tea. Again,this 1H NMR based study proved the possibility of the use of NMR forquality evaluation of beverages by determining the quality relatedchemical constitutes in food with simple sample preparation andshort analysis time (Tarachiwin et al., 2007).

8.3. Edible oils

1H NMR spectroscopy provides a possible alternative to conven-tional chromatographic methods for determining the composition ofoils. Fauhl et al. (2000) separated olive oil, hazelnut and sunfloweroils based on geographic origin (Fauhl et al., 2000). In a more recentstudy, Alonso-Salces, Moreno-Rojas, et al. (2010) identified olive oilsamples from five different countries (Spain, Italy, Greece, Tunisia,Turkey, and Syria) and their corresponding unsaponifiable fractionsusing 1H NMR spectra(Alonso-Salces, Moreno-Rojas, et al., 2010).This study suggested that they contain complementary informationwhich would enhance the classification of olive oil according totheir geographical origin. Likewise, several studies have shown thatNMR spectroscopy is a powerful tool for characterizing olive oilsaccording to cultivar, geographical origin, quality, and genuineness(D'Imperio et al., 2010). Few studies, however, have used this tech-nique to investigate the effect of the harvesting method on olive oilcomposition. D'Imperio et al. (2010) focused on this area of research.Harvestingmethods such as the use of combs or shakers can influencethe composition of unsaturated fatty acid chains and volatile com-pounds in raw olives. This affects olive oil quality as it specifically in-creases in acidity and peroxide values while also causing a decrease intotal polyphenol content. In general, the mechanical harm to fruitsduring harvest can increase several autoxidative processes whichare detrimental to olive quality (D'Imperio et al., 2010).

8.4. Cheese

The potential of NMR to study cheese has been intensively reportedwith some specific topics, such as determining its geographic origin,molecular mobility of water, water holding capacity (Hinrichs et al.,2004; Karoui & De Baerdemaeker, 2007; Summer et al., 2003). Inaddition, Consonni and Cagliani (2008) analyzed Italian ParmigianoReggiano cheese for the identification of ripening and geographicaldiscrimination using NMR. During the ripening process, cheese compo-nents encountermodifications in their chemical, physical and enzymat-ic properties. Researchers realized that the amino acid content may beinfluenced by the ripening and production location showing a highcontent of leucine and isoleucine in the early ripening stages whilethe later ripening stages had high threonine content.When a ParmigianoReggiano cheese was compared with a Grana type cheese from EasternEurope, the latter was rich in lactate, butanoate, acetate, leucine andisoleucine whereas the former had large amounts of other compounds,such as, threonine. These free amino acids and fatty acids alsocontributed to distinctive taste features of those cheeses (Consonni &Cagliani, 2008). With NMR technology, other researchers were able todifferentiate Asiago cheese produced in alpine farms from the samecheese produced commercially in larger operations (Schievano, Pasini,Cozzi, & Mammi, 2008). Results indicated that the FA composition of al-pine farm cheeses had a higher unsaturated FA content (oleic, linoleic,linolenic, and conjugated linoleic acids) compared to the industriallyproduced cheese. Such differences in FA composition can be accountedfor due to the diet of cattle on high-concentrate diets, compared tocattle on Alpine farms where production consists of milk from cattlegrazing on natural pasture grasses at higher elevations. This furtherdemonstrates the importance of the cattle's diet which has the abilityto directly affect the quality of milk and milk products such as cheese.

In a review, several other applications of NMR for cheese analysishave been summarized, including the use of MRI to examine the grossmicrostructure of cheese and to identify the location of holes and slitswithin cheese for quality control purpose; the use of NMR to measuremoisture and fat content, as well as chemical compounds in Parmigia-no Reggiano cheese for investigation of ripening (Everett & Auty,2008). This review also introduced that the utility of NMR to evaluatewater mobility and to identify the more mobile bulk water trappedwithin the casein matrix and a less mobile water phase bound direct-ly to the casein in mozzarella cheese. In addition, NMR results has alsorevealed that ice crystals opened up the protein matrix for permittingthe development of water pockets during the freezing of Mozzarellacheese, as well as diffusion of water molecules and fat globules incheese (Everett & Auty, 2008).

8.5. Fruits and vegetables

By means of the quantification of certain NMR parameters (i.e. T1,T2, and diffusion coefficient (DC) to obtain information about severalprocesses and material properties (such as ice crystallization, andwater mobility), the use of NMR methods to identify compositionsand evaluate quality has also been popular amongst a wide-range offruits and vegetables (Brusewitz & Stone, 1987; Chen et al., 1989).

Studies have applied NMR to leafy vegetables, lettuce samples(Lactucasativa) with a large number of water soluble metabolites weredistinguished along with key organic solvents (Sobolev et al., 2005).“The safety testing of genetically modified organisms (GMOs) is ahigh priority for regulatory authorities, and there is a need for tech-niques capable of detecting any unintended effect following a geneticmodification” (Piccioni et al., 2009). With the increasing awareness ofgenetically modified (GM) foods, Sobolev et al. (2005) used NMR tostudy GM lettuce. This 2010 study compared levels of water solubleme-tabolites between GM lettuce and wild type lettuce resulting in differ-ences in both the glucose and fructose content. Piccioni et al. (2009)touched upon differences between transgenic and traditional maize.Transgenic maize revealed higher levels of certain compounds, includ-ing mainly ethanol, citric acid, glycine–betaine, and trehalose.

Kerr, Kauten, McCarthy, and Reid (1998) studied ice formation andfreezing properties in a variety of foods such as potatoes, carrots, peas,and chicken legs. Freezing is a very important tool in the food industry,allowing for the longer preservation of food. Being able to detectfreezing times, patterns, and time to completion is important for theimprovement of food quality. Using MRI, the freezing behavior charac-teristics were monitored noninvasively in the different foods, the iceformation correlated to the loss of NMR signal intensity, as well as thetime of ice formation to the time of the loss of signal. (Kerr et al., 1998).

NMR data regarding correlation of distribution during cookingcorrelated to texture attributes of potato have also successfully beendemonstrated (Mortensen, Thybo, Bertram, Andersen, & Engelsen,2005; Thybo et al., 2004). For example, in a study by Mortensen et al.(2005), a pulsed NMR analyzer was employed to determine dry matter(DM) content, and investigate water characteristics and water transi-tion between two bins (low DM and medium DM) of potatoes of theSava variety during cooking. DM content was of interest in the study,since DM content is relevant for potato texture and plays a role in themobility of the water (Mortensen et al., 2005). These studies not onlydemonstrated the sensitivity of MRI for determination of structuralchanges with respect to water association during processing and finaltexture of the potato, but also gave scientific support for the develop-ment of NMR methodology for the prediction of sensory texture attri-butes of other fruits and vegetables.

MRI texture analysis (TA) was used to study the effects of ripeningand storage of sliced apples. Here TA refers to a series of techniquesused for the quantification of spatial variation of gray tones in MR im-ages. Certain TA parameters were calculated from MR images of applevarieties during ripening and long-term storage. Different apple


varieties are found to have different dynamics of TA parameters formaturation and storage periods. These TA parameters of particular in-cluded skewness and kurtosis (among histogram-based parameters),and variance of absolute gradient (among gradient-based parameters).In addition, different gray level nonuniformities (among run lengthmatrix-based parameters) and especially some co-occurrencematrix-derived parameters such as correlation, sum average, sum vari-ance and sum entropy (within 1-, 3-, and 5-pixel neighborhoods) werealso found. These above mentioned TA parameters were associatedwith chemical and physical characteristics (firmness of fruits, bruising,soluble solids content (SSC), titratable acids) or three apple varieties(i.e. Topaz, Redspur and Idared) (Létal, Jirák, Šuderlová, & Hájek,2003). MRI texture analysis also applied to study other fruits, such aspears (Lammertyn et al., 2003; Zhou & Li, 2007).

HR NMR spectroscopy has been shown to be a valuable method forthe analysis of low molecular weight compounds in fruit juices whileallowing the simultaneous identification of several sugars, organicacids, amino acids and other minor components such as phenoliccompounds (Duarte et al., 2006). Gil et al. (2000) applied high resolu-tion 1H NMR to examine the composition of natural mango juices (Gilet al., 2000). The value of this study lies in the ability to identify spoil-age and microbial contamination (specifically Penicillium expansum)hence 1H NMR enables earlier detection of the juice compositionaldegradation.

Gonzalez et al. (2010) studied the effects of high pressure andthermal processing on onion cell membranes. In particular, mem-brane permeability and cell compartmentalization were the focussince they are an integral aspect of plant tissue texture (Gonzalez etal., 2010). 1H-NMR proved to be an effective method for the quantifi-cation of cell membrane damage in onions and allowed for the com-parison of the impact of different food processes based on tissueintegrity. These findings can be extended towards other samplessince the quality of fruits and vegetables are related to the degree oftissue integrity.

Researchers have been able to use 1H NMR to obtain informationon the composition of a variety of fermented cocoa beans (Caligiani,Acquotti, Cirlini, & Palla, 2010b). The study determined the aminoacids, polyalcohols, organic acids, sugars, methylxanthines, catechins,and phenols in cocoa beans from different countries (Ecuador, Ghana,Grenada, and Trinidad) demonstrating the method to be a rapidmethod for country identification and quantification of beans. Chenet al. (2010) used LF-NMR to observe the distribution and state ofwater in soybeans. The distribution of water was homogeneous, andthe intensity of distribution increased remarkably with total watercontent (Chen et al., 2010). This proves to be a useful approach to un-derstand the role of water (in different states) in the extrusioncooking process, which is a popular manufacturing process for pre-paring a variety of foods, such as cereals, and snacks.

8.6. Meat and fish

NMR technology continues to be explored in a wide range of dif-ferent meats (i.e. pork, beef and chicken). Several NMR parametershave been found associated with variations of water mobility as con-sequences of the mediations of water macromolecule interactionsand changes in tissue structure, including spin–lattice (T1) andspin–spin (T2) relaxation times, magnetization transfer ratio (MTR),and apparent diffusion coefficient (ADC).

The use of MRI permits the quantification of the above mentionedparameters, which has been used not only to determine chemicalcomposition, muscle structure, and quality of meat, but also tostudy carcass composition, adipose tissue distribution, connectivetissue, and muscle fiber type. These parameters have also been corre-lated with meat properties including pH, water-holding capacity,moisture, texture and sensory attributes (Bonny, Laurent, & Renou,2000; Cernadas, Carrion, Rodriguez, Muriel, & Antequera, 2005;

Graham et al., 2010; Herrero et al., 2007; Jung et al., 2010; Mitchell,Scholz, Wang, & Song, 2001; Renou et al., 2003; Ruiz-Cabrera, Gou,Foucat, Renou, & Daudin, 2004; Shaarani, Nott, & Hall, 2006).

Recent studies have quantified beef (Graham et al., 2010; Jung etal., 2010). The aim of the study by Graham et al. (2010) was to eval-uate the ability of 1H-NMR to characterize the changes in aminoacids, nucleotides, and sugars during post mortem aging. Significant-ly, this method required minimal sample preparation to analyze beefsamples and demonstrated that aging does affect the concentration ofdifferent metabolites. Their study revealed an increase in proteolysisthat ultimately affected the concentration of amino acids.

In order to obtain information regarding the correlations betweenMRI, texture, and physicochemical parameters, three model systems:fibrinogen–thrombin gels (FTG), meat emulsions (ME), and meatemulsion supplemented with fibrinogen–thrombin (ME-FT) wereused in a study. MRI parameters (T2, T1, and apparent diffusion coef-ficient) indicated that systems with fibrinogen and thrombin (FTGand ME-FT) presented a structure with many and large pores, bulkwater, and higher translational motion of water (Herrero et al., 2007).

The increasing awareness of BSE has caused both an interest in andconcern amongst individuals when trying to determine the geographi-cal origin of beef. Jung et al. (2010) used 1H NMR spectroscopy coupledwith multivariate statistical analyses to differentiate the geographicalorigin of beef samples. Samples were examined with the use of metab-olite profiling data. This identified potential marker candidates includ-ing amino acids and succinate which distinguish beef origin.

The main components of smoked salmon have also been identifiedusing NMR spectroscopy (Castejón et al., 2010). This includes the de-termination of docosahexaenoic acid (DHA) and other polyunsaturat-ed FAs along with carbohydrates, amino acids, dipeptides, andorganic acids. Their study created a novel possibility in the determi-nation of ω−3 FAs for fish and processed fish products. Consequent-ly, these methods avoided preparation (chemical pre-treatment) andextraction which are essentially required by other methods. Similarly,Nestor et al. (2010) targeted the avoidance of extractions and deter-mined the FA composition, the eicosapentaenoic acid (EPA) andDHA in Arctic char. This study achieved direct information regardingthe nutritional value of the fish, with a simple analytical technique(Nestor et al., 2010).

Further applications of NMR analysis to fish sample processingmethods were demonstrated with regards to salting (Gudjonsdottiret al., 2010). Salting fish has been a traditional preservation techniquefor centuries in many cultures. These methods involved in the pro-duction of salting cod can impact the distribution of water in codmuscle tissues as well as protein denaturation. By investigating thewater distribution, it indicated that salting and rehydration processesdid irreversibly change the cells. These analytical methods have prov-en to be rapid and non-destructive techniques that can produce valu-able information in an extensive amount of food samples.

9. Conclusion and future research

Research applications described above illustrate that NMR andMRI are valuable tools to study metabolic processes, composition,structural, and physical states of foods, as well as tools for food qualityand process control (Sobolev et al., 2005; Tarachiwin et al., 2007).Spyros and Dais (2009) envisioned that NMR in the future will “playan important role in this field that encompasses many potential appli-cations in food science and analysis” (Spyros & Dais, 2009).

Among many, one of those applications that will become increas-ingly important is to explore the connections between food andhealth sciences. For examples; Weissleder, Poss, Wilkinson, Zhou,and Bogdanov (1995) have made rehydration and dehydration pro-cesses for a food gel suitable for monitoring the controlled releaseand hydrogel volume erosion of an implant in vivo; and Marcianiet al. (2007) have used MRI to investigate the behavior of lipid


emulsions in the human stomach. Another type of application thatwill become more important is verification of labeling claims about:region or species or breed of origin, health properties of pronutrients;and production or processing systems such as organic or minimallyprocessed (Caligiani, Acquotti, Cirlini, & Palla, 2010b; Figueiredo etal., 2006; Marciani et al., 2007; Weissleder et al., 1995).

Modifications of NMR instruments are also needed to improvethe sensitivity to enable improved detection and quantification of foodcomponents. Researchers have made credible attempts; Haiduc, Trezza,van Dusschoten, Reszka, and van Duynhoven (2007) designed anNMR-Mouse that employs new magnet geometry, and Hollingsworthand Johns (2004) and Callaghan (2006) developed techniques to mea-sure non-NMR parameters such as flow and rheological properties, alsoknown as velocimetry MRI or Rheo-NMR (Callaghan, 2006; Haiduc etal., 2007; Hollingsworth & Johns, 2004). Improvements will also be real-ized using synergistic combinations of NMR/MRI and other tools, such asimpedance spectroscopy, ultrasound or laser scattering, and rheologicalmeasurements (Mariette, 2009). For examples, researchers have intro-duced a novel low-cost Halbach-array based NMR system whichfacilitates the simultaneous use of multi-sensor techniques on the samesample; and other workers proposed that low-field NMR technologiesalong with polarization techniques can contribute to the developmentof stable, robust and portable NMR devices (Adams et al., 2009;Trabesinger et al., 2004).

In another study, a site-specific natural isotope fractionation-nuclear magnetic resonance (SNIF-NMR) methodology has been de-veloped to detect added beet or cane sugar in maple syrup. Whenbeet sugar was added, the deuterium/hydrogen (D/H) value obtainedby SNIF-NMR is in good agreement with the values (AOAC OfficialMethod 995.17); however, when cane sugars, or blends of beet andcane sugars, or corn sweeteners were added, SNIF-NMR was unableto perform precise and accurate measurements as before, unlessAOAC Official Method 984.23 (Corn Syrup and Cane Sugar in MapleSyrup) was used with SNIF-NMR (Martin et al., 2001).

In food science, barriers to development of NMR spectroscopy in-struments are primarily due to high cost, the expertise involved, andsafety issues related to magnetic field maintenance. Low-field NMRand MRI are relatively more accessible to food researchers due tolower cost and easier maintenance, but their applications are still lim-ited. It should also be noted that all applications of NMR and/or MRIappears to be research oriented at the present time (Table 1).Extending the application of NMR techniques beyond research to in-dustrial process and quality control is still to come. In order to ensureproper data acquisition and analysis, more NMR-trained staff areneeded in the aspect of food application. Food researchers also facechallenge to establish standard operation procedures (SOPs) ofNMR/MRI analysis for specific categorized food products (i.e. wine,potatoes) due to the complex nature of foods. Once SOPs areestablished, researchers are able to compare their results of NMR/MRI for further improvements. On the other hand, NMR permits di-verse food-based application, but still has limitation. Integratingwith other analyses will provide a full picture of results.

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