NMR spectroscopy applications in food analysis

A. Spyros

NMR Laboratory, Dept. of Chemistry, Univ. of Crete

Spectroscopy Solutions eConference, May 20, 2014

“Food” and “NMR or MRI”

articles in Scopus

(title, keywords or abstract)

Why has NMR become so successful

in food analysis ?

• NMR spectrometers are now more accessible to food scientists

• Sophisticated NMR hardware and user-friendly software has been developed

• 2D NMR spectroscopy has allowed easy metabolite identification

• Ease of use, minimal sample preparation

• Quantitative chemical composition information

• Multivariate statistical analysis tools has enabled food metabolomics and chemometrics

• Public awareness on food safety and quality issues

NMR spectroscopy in food analysis

• Fats and oils

• Beverages

• Fruits and vegetables

• Dairy products

• Meat products

• Whole foods

• Chemical

characterization

• Quality control

• Authentication

• Adulteration

• Genetic modification

• Protected

denomination of origin

L. Mannina et al., Progr. NMR Spectrosc. 66, 1 (2012)

NMR methodology scheme for food analysis -

metabolomics

Solid state NMR

Metabolomics

1H NMR spectrum of beer

Rich compositional information (metabolites)

• Brewing site

• Type (ale, lager)

• Barley or wheat malt

• Production date

• Storage effects

J. E. Rodrigues and A. M. Gil, Magn. Reson. Chem., 2011, 49, S37

Multivariate statistical analysis models-

Metabolomics One metabolite – one line

Many spectra, many metabolites ?

Too much information !

To visualize differences between samples

we need the data to be broken down to

a few components or factors

Metabolomics variants

• Targeted vs untargeted metabolomics

Concentrations of known metabolites vs pure spectra (buckets)

• Unsupervised (PCA, HCA) vs supervised

models (DA, PLS, OPLS-DA, NN, etc.)

The model does not know sample class vs the model knows the

classification already

• Wine

• Beer

• Spirits

• Coffee

• Tea

• Cocoa

• Fruit juices

• Vinegar

• Honey

• Olive oil

• Vegetable oils

Oils and beverages analysis by NMR spectroscopy

Dr Markus Link’s presentation later today

E. F. Boffo et al, LWT - Food Science and Technology, 2009, 42, 1455.

NMR-based metabolomics on teas and

herbal teas

A. Spyros, P. Dais. “NMR Spectroscopy in Food Analysis”, RSC, Cambridge UK, 2013.

Tea metabolomics

A. Ohno et al, J. Agric. Food Chem., 2011, 59, 5181.

Cultivar discrimination of wine : local Cretan

wine cultivars aged in barrels

A. Spyros et al, manuscript in preparation, 2014.

Red wine aging in barrels

A. Spyros et al, manuscript in preparation, 2014.

Quality control of spirits - Cretan raki

MeOH

Acetaldehyde Phenylethanol

Acetate

Ethyl acetate

Alcohols Ethyl lactate

Propanol

3-Me-butanol

2-Me-propanol

Public safety issues (mainly distributed hand in hand,

unbottled and without traceability information)

A. Spyros, unpublished results, 2014.

Controlled compounds in raki

So far no sample was found over the official limits

Methanol (g/100 Lt AA)

Official l imit = 1000

MeOH1

2

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22

0

50

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300

350

Acetaldehyde (g/100 Lt AA)

Official l imit = 500

Ace

1 3 5 8 10 12 14 16 18 20 22

0

2

4

6

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Methanol Acetaldehyde

A. Spyros, unpublished results, 2014.

• Quality Control of olive oil (composition, age)

• Geographical and varietal classification

• Year of production variations

• Detection of adulteration with vegetable oils and

low quality olive oils

NMR spectroscopy in olive oil analysis

Quality control in virgin olive oils

Diglycerides analysis by NMR

• Virgin oils contain 1-3% total DGs

• Fresh virgin oils contain mainly 1,2-DGs

D=1,2-DGs/DGs > 0.9

D is further reduced during storage, thus it is a good index of

aging

A. Spyros, A. Filippidis, P. Dais, J.Agric. Food. Chem., 52, 157 (2004)

Classification of 13 types of vegetable oils

-40 -20 0 20 40 60 80-20

-15

-10

-5

0

5

10

15

20

25

30

virgin olive

soybean

hazelnut

corn

sesame

groundnut

sunflower

almond

safflower

palm

coconut

walnut

rapeseed

Root 2

Root 1

G. Vigli, A. Filippidis, A. Spyros, P. Dais, J.Agric. Food. Chem., 51, 5715 (2003)

Adulteration of olive oil with vegetable oils

Root 1

Ro

ot

2

-15

-10

-5

0

5

10

15

20

25

-30 -20 -10 0 10 20 30

virgin olive

hazelnut

sunflower

soybean

corn

mhazelnut

msun

msoybean

mcorn

Adulteration of virgin olive oil with low

quality olive oils

G. Fragkaki, A. Spyros, G. Siragakis, A. Salivaras, P. Dais, J.Agric. Food. Chem., 53, 2810 (2005)

Lampante

Refined

Extra virgin

NMR analysis of solid and semisolid foods

• Solids foods, due to immobility, provide NMR spectra with broad lines

• Rotation of the sample at the magic angle (θ=54.7o) leading to narrow lines,

just like liquid NMR

• High Resolution Magic Angle Spinning (HR-MAS) is suitable for semisolid

foods

• Cross-Polarization Magic Angle Spinning (CP-MAS) is suitable for rigid

foods, like grains.

Solid state NMR spectroscopy

Normal magnet Special probe MAS rotors

•20-200 mg of sample

• Suitable pulse sequences allow 1D and 2D NMR spectral acquisition

High resolution MAS NMR in food science

• Fruits and vegetables (sweet pepper, mango pulp, apple, tomato), nuts

and grains (wheat, rice, almonds, barley beans, green coffee beans)

• Cheeses (Parmigiano reggiano, emmentaler), meat (dried beef, salmon)

1H HR-MAS study of

ripening of mango juice pulp

1 day

5

15

19

Ala Citric acid

Gil et al., J. Agric. Food Chem. 2000, 48, 1524-1536

1H HR-MAS NMR analysis of triterpenoids

in olive leaves

E. Manolopoulou et al., Magnetic Resonance in Food Science: Food for Thought,

Duynhoven, J. (Ed), RSC, Cambridge UK, 2013, pp. 164-170.

ppm

0.60.81.01.21.41.61.82.02.22.42.62.83.03.2 ppm

20

30

40

50

60

70

80

90

18

3

16 11

9

19a

27

23

30

29

19b

5

24

26

ppm

0.60.81.01.21.41.61.82.02.22.42.62.83.03.2 ppm

20

30

40

50

60

70

80

90

18

3

16 11

9

19a

27

23

30

29

19b

5

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NMR-based metabolomics on vegetables

Vegetable processing: soya beans thawing

MR imaging

Oil

4 min 24 min 44 min 64 min

M. Koizumi et al, Magnetic Resonance Imaging 2006, 24, 1111

NMR-based metabolomics on fruits

A. Spyros, P. Dais. “NMR Spectroscopy in Food Analysis”, RSC, Cambridge UK, 2013.

Post-harvest ripening of fruits by MRI

Distribution of sugars and

lycopene in tomato during ripening

Y. C. Cheng, T. T. Wang, J. H. Chen and T. T. Lin, Postharvest Biol. Tec., 2011, 62, 17.

mature green red ripe

Sugars

Lycopene

Quality evaluation of fruits by MRI

On-line seed detection in mandarins during sorting

N. Hernández-Sánchez, P. Barreiro and J. Ruiz-Cabello, Biosystems Engineering, 2006, 95, 529.

photos

MR images

Motion-corrected

MR images

Meat analysis by HR-MAS NMR

NMR spectra of a sample of Longissimus dorsi muscle of a Friesian Holstein bull

M. Ritota et al. Meat Science 2012 92,754.

NMR-based metabolomics on meat

Y. Jung et al, J. Agric. Food Chem., 2010, 58, 10458.

Discrimination of beef sirloin from

Australia, Korea, New Zealand

and the United States.

NMR-based metabolomics of dairy products

R. Lamanna, A. Braca, E. Di Paolo and G. Imparato, Magn. Reson. Chem., 2011, 49, S22

Discrimination between milk

of different animal origin

sheep

cow

Solid state Cross Polarization MAS 13C NMR spectroscopy

A. Mihhalevski et al. Journal of Agricultural and Food Chemistry 2012, 60, 8492

Whole foods: Rye bread storage

Whole foods: Sausage fermentation

Distribution of 1H T2 relaxation times during fermentation

S.M. Møller, A. Gunvig, and H.C. Bertram Meat Science 2010, 86, 462

Whole foods: Rice cooking

M. Kasai, A. Lewis, F. Marica, S. Ayabe, K. Hatae and C. A. Fyfe, Food Res. Int., 2005, 38, 403.

MRI images obtained at different stages

of rice (cooking time indicated in minutes)

White indicates high water concentration

Many thanks to the

organizers for their

kind invitation,

and

Thank you for your

attention!

aspyros@chemistry.uoc.gr

www.chemistry.uoc.gr/aspyros