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Characterisation of Pomegranate Juicesfrom Ten Cultivars Grown in TurkeyMustafa Cam a , Yasar Hisil b & Gokhan Durmaz ca Erciyes University, Department of Food Engineering, Kayseri,Turkeyb Ege University, Department of Food Engineering, Bornova, Izmir,Turkeyc Inonü University, Department of Food Engineering, Malatya, TurkeyPublished online: 26 Mar 2009.

To cite this article: Mustafa Cam , Yasar Hisil & Gokhan Durmaz (2009) Characterisation ofPomegranate Juices from Ten Cultivars Grown in Turkey, International Journal of Food Properties,12:2, 388-395, DOI: 10.1080/10942910701813917

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International Journal of Food Properties, 12: 388–395, 2009Copyright © Taylor & Francis Group, LLCISSN: 1094-2912 print / 1532-2386 onlineDOI: 10.1080/10942910701813917

388

CHARACTERISATION OF POMEGRANATE JUICES FROM TEN CULTIVARS GROWN IN TURKEY

Mustafa Cam1, Yasar Hisil2, and Gokhan Durmaz3

1Erciyes University, Department of Food Engineering, Kayseri, Turkey2Ege University, Department of Food Engineering, Bornova, Izmir, Turkey3Inonü University, Department of Food Engineering, Malatya, Turkey

Pomegranate juices obtained from ten pomegranate cultivars of Turkey were analysed fortheir sugars, organic acids and the other quality parameters including pH, total soluble solids,and titratable acidity. Statistically significant differences were determined among the culti-vars for parameters analysed. Citric acid was the predominant acid of all the cultivars studied.Cultivar “Zivzik,” one of the most popular cultivar in Turkey, showed best scores for totalsoluble solids (16.9 ± 0.06 ºBrix), glucose (84.18 ± 0.42 g/l) and fructose (83.34 ± 0.81 g/l).Pomegranate juices were classified into three groups according to principal componentanalysis and cluster analysis.

Keywords: Pomegranate, Punica granatum, Sugars, Organic acids, Principal componentanalysis, Cluster analysis.

INTRODUCTION

Pomegranate (Punica granatum L.) is considered one of the oldest known edible fruitand probably originated in northern Turkey.[1] Production of this fruit in 2003 was 73 000 tonsin Turkey [2] and its production amount is increasing sharply year by year. There is a grow-ing interest for this fruit not only because of its pleasant taste, but also having beneficialproperties in the human diet, as it contains several groups of substances that are useful indisease prevention.[3] Popularity of pomegranate based products is mainly due to the sci-entific evidences that suggest a protective role in prevention of oxidation of both low densitylipoprotein and high density lipoprotein,[4] blood pressure and atherosclerosis development.[5]

These beneficial effects of the pomegranate based products were attributed to the antioxi-dative properties of pomegranate polyphenols,[6] and sugar-containing polyphenolic tanninsand anthocyanins.[7]

The edible part of the fruit (arils) contains considerable amount of sugars, vitamins,polysaccharides, polyphenols and minerals.[8,9] Arils is consumed fresh or processed intojuice, jams, syrup, wine, and sauce. There is an increased concern in the fruit juice industryabout the availability of high juice yield pomegranate cultivars with suitable juice compo-sition.[10] Because of market demand, it has become increasingly important to characterize

Received 17 April 2007; accepted 19 November 2007.Address correspondence to Mustafa Cam, Erciyes University, Department of Food Engineering, 38039

Kayseri, Turkey. E-mail: mcam@erciyes.edu.tr

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CHARACTERISATION OF POMEGRANATE JUICES 389

the different varieties and clones to obtain a high quality product with economical interest.Since pomegranate consumption is driven by both fresh market and processing industry, itis crucial to acknowledge all fruit characteristics—not only classify varieties from abotanical point of view but also to meet current market demand for quality fruits.[3]

It is well known and widely accepted that the knowledge of the qualitative and quanti-tative distribution of sugars and acids in fruits, vegetables and several other natural matricesare of primary importance for a number of reasons.[11] Qualitative and quantitative composi-tion of organic acids and soluble sugars has been often regarded as indicator of fruit qualitytraits. In addition, these compounds are important to evaluate fruit maturity, ripeness, and stor-age conditions and could be used as chemical markers in distinguishing different cultivars.[12]

On the other hand, acid content contributes to the flavour and overall acceptability of fruitand high acid containing varieties are sometimes chosen due to their lower calories.

Individual sugars[8,13,14] and organic acids[10,13] of different cultivars of pomegranatehave been published in the literature. However, to the best of the authors’ knowledge,there is negligible data available on sugars and organic acids of these ten cultivars of Turkey.The objective of this study was the quantitative determination of sugars, organic acids andsome analytical properties of pomegranate juices (PJs) obtained from ten pomegranatecultivars grown in Turkey. Principal component analysis (PCA) and cluster analysis (CA)were applied to the data obtained in order to separate the PJs into homogeneous groups.

MATERIALS AND METHODS

Pomegranate Cultivars

Nine pomegranate cultivars of Izmir city were studied: Izmir 8 (I8), Izmir 10 (I10),Izmir 16 (I16), Izmir 23 (I23), Izmir 26 (I26), Izmir 1264 (I1264), Izmir 1479 (I1479),Izmir 1499 (I1499), Izmir 1513 (I1513). The cultivars were selected according to twomain criteria: popularity for fresh consumption, preferred by industry and representativemembers of their own class. I8, I10, I16, I23, I26, and I1479 are sweet cultivars; I1264,I1499, and I1513 are sour cultivars. These nine cultivars were harvested in October 2006when fully mature from the orchard of Aegean Agricultural Research Institute. One pome-granate cultivar namely Zivzik (ZZ), one of the most popular cultivar in Turkey, was sup-plied from Directorate of the Ministry of Agriculture (Siirt).

Approximately 7 kg of pomegranate fruit was sampled for each cultivar. Injured andsunburned fruits were discarded. The pomegranate fruits were peeled and the skins cover-ing seeds were removed manually. The juice of the seeds was extracted with a pilot plantpackaged-type press (Bucher, Switzerland). The juices were kept at – 40°C until analysis.

Analytical Determinations

The PJs were defrosted and then centrifuged at 4000 rpm for 15 min at 4°C in orderto remove water insoluble particles. The pH measurements were performed using a NELpH 821 model pH meter at 20°C. Titratable acidty (TA) was determined potentiometri-cally and expressed as g citric acid per 100 g juice. Total soluble solids (TSS) in ºBrix wasdetermined by using a Bellingham+Stanley RFM 330 refractometer. Maturity index wascalculated by dividing TSS to TA.

Organic acids were analyzed with Hewlett-Packard 1050 series pumping system, aWaters 486 UV-detector. Reversed phase separations were carried out with a 250 × 4 mm

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390 CAM, HISIL, AND DURMAZ

i.d., 5 mm HiChrom C18 column. Extraction and analysis conditions of PJs were describedextensively elsewhere.[10]

Sugars were analyzed with the same HPLC equipment using refractive index detector.PJs were filtered through a Sep-Pak C18 cartridge to remove interferences.[13] Separationsof sugars were performed on a 250 × 4.6 mm i.d., 5 mm, Zorbax NH2 analytical column at25°C. Elution was carried out using 75% aqueous acetonitrile at a flow rate of 1.5 ml/minas the mobile phase. Organic acids and sugars were identified by comparison of theirretention times with those of authentic standards and spiking tests. Quantification of com-ponents was based on external standard method.

Data Processing

Analysis of variance (ANOVA) was applied to the data. Means corresponding ofeach cultivar were compared using Duncan’s multiple range test (P < 0.05). Principalcomponent analysis (PCA) and cluster analysis (CA) were carried out using the SPSS10.0.1 statistical software package for Windows (SPSS Inc., Chicago, USA).

RESULTS AND DISCUSSION

Physical and Physicochemical Parameters

One of the most important parameters from an industrial point of view is the juice contentof the seeds. The juice yield of ten pomegranate cultivars was found within 65.0–81.6 g/100 gseed. The highest juice yield was in Izmir 23 (81.6 g/100 g seed) and the lowest in Izmir1264 (65.0 g/100 g). The juice content of pomegranate fruits accounts for about 45-65 g/100 g whole fruit or 75–85 g/100 g arils.[10] Table 1 presents the description of cultivarsand the values of some analytical properties affecting the pomegranate’s quality includingpH, TA, TSS and maturity index. Maturity index (TSS/TA) was used by some authors toclassify the pomegranate varieties.[3,15] The following classification has been establishedfor Spanish varieties: maturity index (MI) = 5–7 for sour, MI = 17–24 for sour-sweet andMI = 31–98 for sweet varieties. Taking into consideration this simple rule, the following

Table 1 Some analytical properties of pomegranate juices.a,b

Cultivars pH TA (g/100 g juice) TSS (ºBrix) MI (TSS/TA) Description

I8 3.24 ± 0.01c 0.45 ± 0.02e 16.3 ± 0.06c 35.95 ± 1.90c SweetI10 3.17 ± 0.02d 0.44 ± 0.01e 16.8 ± 0.01a 38.47 ± 0.56c SweetI16 3.21 ± 0.05cd 0.43 ± 0.01e 16.1 ± 0.11c 37.53 ± 0.65c SweetI23 3.85 ± 0.02a 0.25 ± 0.03f 15.6 ± 0.06d 63.03 ± 8.30b SweetI26 3.81 ± 0.06a 0.23 ± 0.01f 15.6 ± 0.01d 68.84 ± 1.41a SweetI1264 2.89 ± 0.07e 2.06 ± 0.14c 16.1 ± 0.11c 7.85 ± 0.58e SourI1479 3.84 ± 0.02a 0.23 ± 0.01f 15.5 ± 0.06d 66.31 ± 1.51ab SweetI1499 2.82 ± 0.03f 2.58 ± 0.03a 16.6 ± 0.06b 6.42 ± 0.11e SourI1513 2.84 ± 0.06ef 2.40 ± 0.01b 16.8 ± 0.06a 6.99 ± 3.01e SourZZ 3.75 ± 0.02b 0.60 ± 0.01d 16.9 ± 0.06a 27.96 ± 0.44d Sour-sweet

aData are the means ± S.D of three replications. bValues corresponding to the different pomegranate juices inthe same column followed by different superscript letters are significantly different according to Duncan’s test(P < 0.05).

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classification of cultivars can be concluded: I8, I10, I16, I23, I26, I1479 as sweet; I1264,I1499, I1513 as sour and ZZ as sour-sweet.

On average, the lowest pH value was obtained for I1499 (pH 2.82) and the highestfor I23 (pH 3.85). The lowest TA was found for I26 and I1479 (TA = 0.23 g/100 g juice)and the highest for I1499 (TA = 2.58 g/100 g juice). Significant differences among somecultivars were determined for TSS and sugars, the two mostly used parameters to deter-mine the quality of fruit juices. The highest TSS content was found 16.9 °Brix for ZZ andthe lowest was found 15.5 °Brix for I1479.

TA, pH, and TSS values have been reported for 13 pomegranate varieties from Turkeyas 0.46–1.73 g/100 g juice, 3.29–3.93 and 16.0–19.0 °Brix,[10] 10 varieties from Iran as0.40–2.45 g/100 g juice, 2.90–4.21, and 10.0–16.5 °Brix,[8], 31 varieties from Tunisia as0.25-3.17 g/100 g juice, 2.93–4.60, and 13.3–16.9 °Brix.[16] Sum of individual acids of 40varieties from Spain have been reported as 0.22–2.92 g/100 g juice.[13]

Sugars and Organic Acids

The composition of PJs showed significant differences (p < 0.05) among the culti-vars in terms of glucose, fructose, citric acid, oxalic acid and malic acid content (Table 2).Three organic acids were determined and quantified in PJs. Citric acid was found as mainorganic acids of all the juices. The concentration of citric acid ranged between 1.35–22.94g/l. Among the cultivars, the highest citric acid level was found for I1513 (22.94 g/l) andthe lowest for I26 (1.35 g/l). Oxalic acid was found the second dominant acid for the culti-vars of I8 (1.75 g/l), I10 (1.77 g/l) and I16 (1.66 g/l). On the other hand, malic acid wasfound the second dominant acids of the other cultivars. Its concentration ranged between0.51 and 0.94 g/l.

In the present study, three organic acids including citric, malic and oxalic weredetermined in ten pomegranate cultivars. Citric, malic and oxalic acid levels agree withthe range in the literature values. However, in addition to these acids, tartaric, quinic,[10,13]

lactic, succinic, acetic, and fumaric acids[13] were determined in some pomegranate cultivars atminor or trace amounts.

Glucose and fructose were detected and quantified in all PJs. Glucose was found asmain sugar of four cultivars namely I26, I1479, I1513, and ZZ while fructose was main

Table 2 Sugars and organic acids of pomegranate juicesa,b, (g/l).

Cultivars Glucose Fructose Citric acid Oxalic acid Malic acid

I8 77.93 ± 1.50c 80.39 ± 1.93c 1.95 ± 0.05e 1.75 ± 0.05b 0.81 ± 0.02c

I10 78.71 ± 3.79b 81.33 ± 3.27b 1.84 ± 0.03f 1.77 ± 0.01a 0.73 ± 0.01d

I16 77.99 ± 0.50c 78.84 ± 1.44e 1.76 ± 0.01g 1.66 ± 0.01c 0.94 ± 0.04a

I23 77.22 ± 0.77d 79.48 ± 0.65d 1.49 ± 0.03h 0.22 ± 0.01g 0.74 ± 0.01d

I26 78.53 ± 0.72b 77.50 ± 2.58f 1.35 ± 0.05i 0.25 ± 0.01e 0.81 ± 0.01c

I1264 70.96 ± 0.29g 71.23 ± 0.89i 19.94 ± 0.53c 0.05 ± 0.01j 0.54 ± 0.02e

I1479 78.63 ± 2.20b 78.50 ± 2.14e 1.78 ± 0.13fg 0.26 ± 0.01d 0.80 ± 0.06c

I1499 73.96 ± 0.19f 74.62 ± 1.93g 22.57 ± 0.39b 0.24 ± 0.01f 0.88 ± 0.14b

I1513 75.02 ± 1.71e 74.07 ± 1.40h 22.94 ± 0.05a 0.16 ± 0.01h 0.55 ± 0.03e

ZZ 84.18 ± 0.42a 83.34 ± 0.81a 5.34 ± 0.06d 0.13 ± 0.01i 0.51 ± 0.01f

aData are the means ± S.D of three replications. bValues corresponding to the different pomegranate juices inthe same column followed by different superscript letters are significantly different according to Duncan’s test(P < 0.05).

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sugar of the rest of the cultivars. The highest glucose (84.18 g/l) and fructose (83.34 g/l)levels was determined in ZZ while the lowest levels of glucose (70.96 g/l) and fructose(71.23 g/l) was observed in I1264.

Generally, sweet varieties have higher glucose and fructose levels than sour varieties.Glucose and fructose level of sour cultivars (I1264, I1499, I1513) were lower than theother cultivars. The range of glucose and fructose contents cultivars in the present studyagrees with literature values[8,13,17] except ZZ, which has higher glucose and fructose levelsthan literature values. Sucrose and maltose were not detected in all cultivars studied, how-ever, they were found in some Spanish cultivars minor or trace amounts.[13] This maybedue to the differences among cultivars, growing seasons, other agricultural practices, andanalytical methods used to determine the individual sugars.

Principal Component Analysis (PCA)

PCA, an unsupervised clustering method, can be used as a form of variable reduc-tion, reducing the large original dataset to a much smaller more manageable dataset (e.g.,consisting of three principal components) which can be interpreted more easily, while pre-serving most of the variance within it.[18,19] In addition, PCA helps to find out in whatrespect one sample is different from another and which variables contribute most to thisdifference.[20]

Factor analysis using PCA as method for the extraction of factors was applied to the10 PJs. By using Kaiser’s rule, three principal components were extracted from the data.The loadings, eigenvalues, and percent of cumulative variance obtained from the PCAanalysis are shown in Table 3. Loading values higher than 0.7 are marked throughoutTable 3 in boldface type. After PCA, the dimensionality of data was reduced from 10 par-tially correlated variables to three uncorrelated PCs with almost 5.2% loss of variation.The PC1 correlates well with the original variables in decreasing order as TA, citric acid,MI, pH, fructose and glucose. PC2 correlates well with TSS. PC3 correlates well withmalic and oxalic acids.

PCA was then used to determine the similarities among PJs obtained from ten cultivars.The projection of the scores on the plane of PC1 and PC3 in Fig. 1 generated three maingroups. Down at center (I1264, I1499, I1513) are sour cultivars. At the upper center of Fig 1are sweet cultivars (I23, I26, I1479), which have higher MI values. At he upper right corner of

Table 3 Loadings, eigenvalues, and percent of cumulative variancefor the three principal components.

Variable PC1 PC2 PC3

pH 0.863 −0.276 −0.414TA −0.982 −0.02 −0.003TSS −0.474 0.857 −0.141MI 0.902 −0.391 −0.0007Citric acid -0.979 −0.006 −0.112Malic acid 0.383 −0.189 0.797Oxalic acid 0.338 0.558 0.716Fructose 0.810 0.544 −0.137Glucose 0.755 0.472 −0.373Eigenvalue 5.191 1.833 1.511% Cumulative 57.679 78.045 94.829

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CHARACTERISATION OF POMEGRANATE JUICES 393

Fig 1 are sweet cultivars (I8, I10, I16) which have lower MI values than the other sweetcultivars. At the upper left corner of Fig 1 is ZZ, which is a sour-sweet cultivar.

Cluster Analysis (CA)

CA is a multivariate procedure for classifying objects into groups. Numerous clus-tering algorithms can be found in the literature. The results obtained from hierarchical CAusing between groups linkage method are shown as a dendogram in Fig. 2. Three clusters werefound which corresponded to the 10 PJs from each cultivar (Rescaled distance cluster

Figure 1 Scatterplot of the scores of the PJs projected to the PC1 and PC3 plane.

–2.0 –1.0 0.0 1.0pc3

–1.5

–1.0

–0.5

0.0

0.5

pc1

810

1623 26

1264

1479

14991513

zz

Figure 2 Dendogram of cluster analysis of pomegranate juices.

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394 CAM, HISIL, AND DURMAZ

combine <2.5). The first cluster was composed of cultivars I26, I1479 and I23. The secondcluster grouped cultivars I8, I16, I10 and ZZ. The third cluster was composed of I1264,I1499 and I1513. CA results agreed with those obtained by PCA.

CONCLUSION

In this study, 10 pomegranate cultivars were analysed for sugars, organic acids, andother quality parameters including pH, TSS, TA, and MI. All cultivars studied displayedhigh TSS content, which is very important parameter for pomegranate juice production.Statistically significant differences were observed among the cultivars for analytical mea-surements. The type of cultivar affected the composition of the pomegranate juiceslargely. Results of this study could be useful to food technologists, horticulture researchersand nutritionists in order to determine the superior cultivars for production of PJs, classifythe cultivars according to their properties and select the proper cultivar(s) from a nutri-tional point of view. Other parameters such as phenolic compounds, vitamins, antioxidantactivities should be revealed by further studies.

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