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Seasonal and cultivar variations in antioxidant and sensory quality of pomegranate (Punica granatum L.) fruit
Journal of Food Composition and Analysis 22 (2009) 189–195
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Original Article
Seasonal and cultivar variations in antioxidant and sensory quality of pomegranate (Punica granatum L.) fruit Hamutal Borochov-Neori a,*, Sylvie Judeinstein a, Effi Tripler a, Moti Harari a, Amnon Greenberg a, Ilan Shomer b, Doron Holland c a b c
Southern Arava Research and Development, Hevel Eilot, 88820, Israel Agricultural Research Organization, Department of Food Science, The Volcani Center, P.O. Box 6, Bet Dagan, 50250, Israel Agricultural Research Organization, Department of Horticulture, Newe Ya’ar Research Center, P.O. Box 1021, Ramat Yishay, 30095, Israel
A R T I C L E I N F O
A B S T R A C T
Article history: Received 14 August 2007 Received in revised form 5 October 2008 Accepted 27 October 2008
Fruits of diverse pomegranate (Punica granatum L.) cultivars were analyzed for soluble phenolics content, antioxidant activity, soluble solid concentration, acidity and internal red color intensity. Analysis was carried out at various dates throughout the harvest season, corresponding to different climatic conditions during fruit ripening. Values obtained varied with cultivar and ripening date. In three cultivars of different sensory properties and harvest season, comparison between late- and earlyripening fruit revealed that arils of fruit ripening later in the season contained more soluble phenolics (1.21–1.71 compared to 0.22–0.88 pyrogallol equivalents, g L1) and exhibited a higher antioxidant activity, as measured by the ferric reducing ability (FRAP) assay (1.22–2.37 compared to 0.86–1.95 vitamin C equivalents, g L1). The red color intensity of the arils inversely related (R2 = 0.89–0.94) to the sum of heat units accumulated during fruit ripening. Multiple linear regression analysis on fruit characteristics in 11 diverse cultivars indicated that juice antioxidative capacity linearly correlated with soluble phenolics content (R2 = 0.98), but not with the red color intensity of the arils (R2 = 0.38). Also, no significant correlation was established between aril color and either juice pH or total soluble phenolics content. The results imply that pomegranate fruit antioxidant and sensory quality traits can be enhanced by the choice of cultivar and controlled-climate cultivation management. ß 2009 Elsevier Inc. All rights reserved.
Keywords: Pomegranate Punica granatum L. Anthocyanins Antioxidants Antioxidative capacity Cultivar Climatic conditions Fruit quality Phenolics Biodiversity and nutrition Food analysis Food composition
1. Introduction The pomegranate (Punica granatum L.) fruit is highly valued for its health-promoting effects in reducing the risk of cardiovascular and other chronic disorders. This claim is supported by the results of an increasing number of clinical studies in both humans and animals (Lee and Watson, 1998; Aviram et al., 2000, 2004; Aviram and Dornfeld, 2001; Kaplan et al., 2001; de Nigris et al., 2005) and in vitro experiments in tumor and macrophage cell cultures (KimNamDeuk et al., 2002; de Nigris et al., 2005; Fuhrman et al., 2005; Seeram et al., 2005). The beneficial health qualities have been attributed to the exceptionally high antioxidative capacity (AOC) of the fruit juice (Gil et al., 2000; Akay et al., 2001), seemingly the result of the remarkably high content and unique composition of soluble phenolic compounds (Gil et al., 2000; Poyrazoglu et al., 2002; Seeram et al., 2005). Phenolic concentration and composition in the pomegranate fruit are cultivar-dependent; the most
* Corresponding author. Tel.: +972 8 6355747; fax: +972 8 6355730. E-mail address: [email protected] (H. Borochov-Neori). 0889-1575/$ – see front matter ß 2009 Elsevier Inc. All rights reserved. doi:10.1016/j.jfca.2008.10.011
abundant components are anthocyanins, catechins, ellagic tannins, gallic and ellagic acids (El-Nemr et al., 1990; de Pascual-Teresa et al., 2000; Gil et al., 2000; Poyrazoglu et al., 2002). The in vivo and in vitro studies described in the scientific literature were conducted with pomegranate juice prepared from fruit of the more popular cultivars (CVs), typified by an intense internal red color. Thus, a special significance was proposed for the anthocyanins (Noda et al., 2002), the molecular red color origin of the fruit juice (Gil et al., 1995; Hernandez et al., 1999). It appears, however, that anthocyanin bioavailability is lower than that of other soluble polyphenolics, such as phenolic acids, isoflavones and catechins (Scalbert and Williamson, 2000; Perez-Vincente et al., 2002; Manach et al., 2004, 2005). To date, no comparative studies were reported on the health-promoting effects of pomegranate juice from cultivars of a less intense internal red color. In addition, the physical and chemical properties of the fruit are highly dependent on the season of development and ripening (Ben-Arie et al., 1984; Badenes et al., 1998; Borochov-Neori and Shomer, 2001; Dumas et al., 2003; Toor et al., 2006; Raffo et al., 2006). The reported in vivo and in vitro studies employed pomegranate juice prepared from commercial harvests, where
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cultivar, level of ripening, agricultural practices and harvest date reflect grower and producer preferences that do not necessarily match health-promoting objectives. To accurately assess the health value in pomegranate fruit and juice consumption, it is important to examine cultivar and seasonal variations in antioxidant content and activity. The present study aimed to develop knowledge on cultivar and seasonal differences in pomegranate fruit antioxidant and sensory quality traits. To achieve this objective, a diverse collection of pomegranate cultivars differing in fruit internal color (from white to deep red), taste (from sour to sweet) and ripening season (from early summer to late autumn) was examined on several ripening dates throughout the harvest season (mid-July to end of October); aril dimension and color as well as juice content, soluble phenolics concentration, antioxidative capacity, pH and total soluble solid (TSS) content were measured. The results were used to test for correlations between fruit antioxidant and sensory-related parameters and explore the role of climate factors. 2. Materials and methods Fresh ripe pomegranate (P. granatum L.) fruits were analyzed. The fruit were sampled from the pomegranate orchard at the Experimental Farm of the southern Arava R&D situated in the Israeli southern Arava Valley (latitude 298530 N; longitude 35830 E), which is characterized by desert climate (Fig. 1) and inferior water quality (electrical conductivity of 3.5 dS m1). The pomegranate plot accommodates trees of 11 cultivars originally from the collection of Assaf et al., Newe Ya’ar Research Center, ARO [registered in the Israel Gene Bank for Agricultural Crops (IGB, web site: http://igb.agri.gov.il)]. The manuscript summarizes studies conducted during 14 August–25 October 2002 and 12 July–25 October in 2004 and 2005, respectively. On each sampling date newly ripened fruit were selected by external criteria according to customary grower practices; the latter include external color, size and shape. The fruit were cooled and studied within 24 h. Each measurement was repeated on five fruits of a similar size from different trees and locations in the orchard, i.e. five replicates. Analytical assays were carried out in triplicates. Intact arils were separated from the pith and carpellary membranes by hand and ripeness was further assessed by tasting; only non-astringent, edible fruit were analyzed. The separated arils
were counted and weighed. Surface color measurements were performed on uniform 3-cm-thick layers of separated arils using a chromameter equipped with a glass light projection tube (CR-300 and CR-A33e, Minolta, Japan). The color was expressed in CIELAB coordinates, where positive ‘‘a*’’ and ‘‘b*’’ represent the red and yellow components, respectively, and ‘‘L*’’ conveys the luminosity dimension, ranging from 0 (pure black) to 100 (white, calibrated against the white reference plate provided with the chromameter). Juice was prepared from isolated arils by a solid fruit juice extractor (Juice Extractor, Model Le Duo, Magimix, France); it was then weighed and immediately analyzed. pH was measured using a specialized food electrode (pH 211 microprocessor pH meter and FC 200B food electrode, Hanna Instruments, Romania). TSS concentration in % was evaluated with a hand refractometer (ATAGO, ATC-1E, Brix 0–32%, Japan). Pomegranate juice was extracted (1:3, v/v) with 80% methanol supplemented with 2 mM NaF, centrifuged (10,000 rpm for 10 min at 4 8C, Sorvall Instruments RC5C) and the supernatant diluted 10-fold with double distilled water (DDW). Concentration of total soluble phenolics was measured colorimetrically with Folin-Ciocalteau 2N phenol reagent (SIGMA Chemical Co, USA) according to Singleton and Rossi (1965). Aliquots of 100 mL were added to 900 mL reaction solution consisting of 200 mL freshly prepared 10-fold diluted Folin-Ciocalteau reagent, 100 mL Na2CO3 and 600 mL DDW. Pyrogallol (SIGMA Chemical Co, USA) was used for the calibration curve (0–100 mg mL1). The absorbance at 765 nm was measured with a spectrophotometer (SHIMADZU Corporation, UV-1650PC, Kyoto, Japan) after 1-h incubation, and the results were expressed in pyrogallol equivalents. AOC was measured by the colorimetric test originally developed to assess the ferric reducing ability of plasma (FRAP) (Benzie and Straino, 1996); the assay was shown to be appropriate for AOC estimation in pomegranate juice (Gil et al., 2000). Clear methanolic extract was prepared as described earlier and diluted 10- to 20-fold with DDW. Fifty microliters were added to 950 mL freshly prepared FRAP working solution [50 mL 300 mM acetate buffer + 5 mL 10 mM 2,4,6-tripyridyl-s-triazine (TPTZ) + 5 mL 20 mM ferric chloride] in a 37 8C water bath. Absorbance at 593 nm was measured with a spectrophotometer (SHIMADZU Corporation, UV-1650PC, Kyoto, Japan) after 4 min. Vitamin C (Fluka, Switzerland) was used for the calibration curve (0–100 mg mL1), and the results were expressed in terms of vitamin C equivalents.
Fig. 1. Climatic data for the Israeli southern Arava Valley (latitude 298530 N; longitude 35830 E). The values are the long-term averages obtained from the local meteorological station during the years 1995–2005. (A) Maximal and minimal air temperature. (B) Maximal and minimal relative humidity (RH). (C) Daily evaporation. (D) Rainfall.
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Fruit physical parameters (juice content, weight and number of arils, and internal red color intensity) and aril juice TSS were determined during three harvest seasons (2002, 2004 and 2005). AOC, total soluble phenolics and pH measurements were conducted during the harvest seasons of 2004 and 2005. The experimental values for each sampling date are the average and standard deviation of measurements performed on five fruits from different trees and repeated for two or three harvest seasons. 3. Results 3.1. Fruit analysis throughout the harvest season Ripe pomegranate fruit of three CVs were studied on several dates throughout the harvest season in the years 2002, 2004 and 2005 (Figs. 2–5). The cultivars, identified here by Newe Ya’ar code system (IGB, web site: http://igb.agri.gov.il), represent three distinct types of the crop: P.G. 128-29 – internally red, sweet, early-ripening (early-CV); P.G. 119-20 – internally pink, sweet, early to mid-season ripening (mid-CV); P.G. 101-2 – internally red, sweet and sour, late-ripening (late-CV). The early-CV started yielding ripe fruits on July 12, the first sampling date. Fruits of the mid- and late-CVs reached ripeness approximately 1 and 2 months later, respectively. Once ripening began, newly ripened fruit were available on the selected sampling dates throughout the study period. In the early-CV, fruit juice content (Fig. 2) was considerably lower in early July and October compared to end of July to end of September. Also, with the progression in harvest season aril weight increased; concomitantly, the number of arils per fruit decreased.
Fig. 3. Aril color measurements throughout the harvest season in ripe fruit of three pomegranate CVs. (A) Late-CV (P.G. 101-2). (B) Mid-CV (P.G. 119-20). (C) Early-CV (P.G. 128-29). ‘‘L*’’, luminosity; ‘‘a*’’, red component; ‘‘b*’’, yellow component.
Unlike the early-CV, in the mid- and late-CVs, fruit juice content as well as aril weight and number (Fig. 2) did not significantly change during the entire sampling period. Fruit aril color varied throughout the season (Fig. 3). Red color intensity (a*) of arils from the early-CV decreased from July to September and increased
Fig. 2. Physical parameters throughout the harvest season of the edible portion of ripe pomegranate fruit in three CVs: P.G. 128-29 (early-CV, *), P.G. 119-20 (midCV, &), P.G. 101-2 (late-CV, D). (A) Number of arils per fruit. (B) Weight of a single aril. (C) Weight fraction of aril juice.
Fig. 4. Correlation analysis between red color intensity of the aril, ‘‘a*’’, and the sum of heat units accumulated during the last 6 weeks of fruit development and ripening. Lines are the best-fit curves obtained by linear (early-CV, P.G. 128-29) and reciprocal (late-CV, P.G. 101-2) regression analyses.
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Fig. 5. Chemical parameters throughout the harvest season of freshly extracted aril juice from ripe fruit of three pomegranate CVs: early-CV (P.G. 128-29, *), mid-CV (P.G. 119-20, &), late-CV (P.G. 101-2, D). (A) TSS; (B) pH; (C) Total soluble phenolics content; (D) AOC. The total soluble phenolics content and AOC are in g L1 pyrogallol and vitamin C equivalents, respectively.
on later sampling dates; the luminosity (L*) declined concurrently. Arils of the mid-CV were initially white and gradually changed to pink during October as reflected by the small increase in ‘‘a*’’ and decrease in ‘‘L*’’. In arils of the late-CV, ‘‘a*’’ developed slowly in September and more quickly in October, with ‘‘L*’’ decreasing concomitantly. The extent of internal red color development in relation to the local temperatures during fruit development and ripening was examined in the early- and late-CVs (Fig. 4). In ripe fruit arils, ‘‘a*’’ inversely related to the sum of heat units (Wang, 1960) accumulated during 6 weeks prior to harvest. In calculating the accumulated heat, daily heat units were defined as the difference, in Celsius degrees, between the daily average temperature and 25 8C. A heat unit value of zero was assigned when the average daily temperature was less than 25 8C. Regression analysis of the data gave best fit to inverse linear (R2 = 0.89) and reciprocal (R2 = 0.94) correlations for the early- and late-CV, respectively. Similar inverse correlations were obtained when shorter periods of heat accumulation were considered (Table 1). The chemical parameters of fresh juice extracted from the separated arils changed throughout the sampling season (Fig. 5). TSS (Fig. 5A) increased with the advancement in ripening date, reaching approximately 15.5% in the three CVs. Juice pH increased from 3.8 to 4.2 between July and August in the early-CV; in all three CVs the pH (Fig. 5B) was constant in fruit that ripened during August and September and decreased in fruit ripening in October. Highest and lowest pH values were measured in the early- and late-CVs, 3.8–4.2 and 3.2–3.4, respectively. The content of total soluble phenolics (Fig. 5C) slightly decreased in the early-CV between mid-July and mid-August (from 0.44 to 0.39 pyrogallol Table 1 Correlation analysis between red color intensity of arils, ‘‘a*’’, and heat unit accumulation during fruit development and ripening. Correlation coefficients (R2) derived from linear [early-CV (P.G. 128-29)] and reciprocal [late-CV (P.G. 101-2)] regression analyses are presented. Period of heat unit accumulation (weeks prior to harvest) 2 4 6
Correlation coefficient (R2) P.G. 128-29
P.G. 101-2
0.84 0.89 0.89
0.78 0.91 0.94
equivalents, g L1) and was significantly higher in fruits of all three CVs that ripened on later dates, reaching values in the range of 1.2–1.7 pyrogallol equivalents, g L1, depending on the CV. The antioxidative capacity (Fig. 5D) followed a similar trend with a decrease in the early-CV from mid-July to mid-August (from 1.95 to 1.54 vitamin C equivalents, g L1) and an increase later in the season for all three CVs, reaching values in the range of 1.2–2.4 vitamin C equivalents, g L1, depending on the CV. Both parameters (total phenolics and antioxidative capacity) were lower in the mid-CV compared to both the early- and late-CVs. 3.2. Interrelations between aril color and chemical parameters Eleven pomegranate CVs representing an extensive assortment of color and taste qualities as well as ripening season were studied (Table 2). Color measurements on separated arils and chemical analysis of the extracted juice were performed on freshly ripened fruit collected on the same date, i.e. exposed to similar climatic conditions during ripening. Each CV had a characteristic set of color and chemical values (Table 2). Every pair of parameters was tested by regression analysis for potential interrelationship (Fig. 6). The antioxidative capacity and total soluble phenolics content were linearly correlated (Fig. 6A; y = 1.52x 0.27, R2 = 0.98). Poor linear correlation was found for the antioxidative capacity as a function of the internal red color intensity (Fig. 6B; y = 0.05x + 1.09, R2 = 0.38). The intensity of the red color of the arils did not correlate with either the total soluble phenolics concentration (Fig. 6C) or the pH (Fig. 6D). 4. Discussion The growing number of scientific reports on the health benefits of the pomegranate fruits (Lee and Watson, 1998; Aviram et al., 2000, 2004; Aviram and Dornfeld, 2001; Kaplan et al., 2001; de Nigris et al., 2005) has generated a significant increase in consumer interest in and, consequently, agricultural production of the crop. To assure consumer satisfaction and producer profitability, it is particularly important to ensure both high content of health-promoting nutrients and fruit attractiveness for either fruit or juice consumption. In this context, the present study demonstrates that pomegranate antioxidant and sensory quality depend on cultivar and climatic conditions during fruit maturation and ripening.
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Table 2 Properties of ripe pomegranate fruit from 11 CVs grown in the Israeli southern Arava Valley. The values are the average standard deviation of measurements during two harvest seasons. CV (Newe Ya’ar code no.)
Ripening season
Aril taste
Aril color
Red color intensity (a*)
TSS (%)
pH
Total soluble phenolics (pyrogallol equivalents, g L1)
Antioxidative capacity (vitamin C equivalents, g L1)
P.G. P.G. P.G. P.G. P.G. P.G. P.G. P.G. P.G. P.G. P.G.
Mid Early Late Late Mid Mid Early Late Mid Mid Mid
Sweet Sweet Sour Sweet Sour Sour Sweet Sour Sweet Sweet Sweet
Light pink Dark red Bright red Pink Light pink Light pink Red Red Dark pink Pink Light pink
9.2 0.5 34.1 1.1 19.4 1.7 13.5 0.5 9.9 0.5 10.4 0.5 24.8 1.5 24.5 1.0 16.9 1.0 12.3 0.5 10.4 0.5
14.6 0.3 15.2 0.1 15.9 0.5 13.5 0.3 14.3 0.3 14.7 0.5 14.2 0.4 15.2 0.3 15.0 0.3 15.0 0.2 13.1 0.2
3.7 0.1 4.0 0.1 3.4 0.1 3.9 0.1 3.9 0.1 3.7 0.1 3.8 0.1 3.0 0.1 3.6 0.1 3.7 0.1 4.5 0.1
1.21 0.09 1.53 0.01 1.71 0.13 1.37 0.05 1.06 0.05 1.58 0.08 1.60 0.07 2.26 0.08 1.04 0.05 0.99 0.04 1.09 0.04
1.46 0.04 2.18 0.02 2.21 0.19 1.90 0.05 1.30 0.07 2.16 0.10 2.09 0.08 3.16 0.11 1.34 0.04 1.25 0.06 1.33 0.05
119-20 128-29 101-2 127-28 118-19 104-5 130-31 116-17 114-15 105-6 106-7
Fig. 6. Tests for correlations between pairs of ripe pomegranate fruit parameters: (A) antioxidative capacity (AOC) vs. total soluble phenolics content; (B) AOC vs. ‘‘a*’’ (aril red color intensity); (C) ‘‘a*’’ vs. total soluble phenolics content; (D) ‘‘a*’’ vs. juice pH. Each point in each figure presents 1 of 11 pomegranate CVs. AOC and total soluble phenolics content are in g L1 vitamin C and pyrogallol equivalents, respectively.
The different ripening dates examined throughout the harvest season signify distinct regimes of climatic conditions during fruit development and ripening. In three pomegranate cultivars differing in sensory qualities and ripening season, aril color as well as the pH, TSS, total soluble phenolics content and antioxidative capacity of the extracted juice varied with ripening date in a similar fashion and on a comparable time scale (when applicable) despite cultivar diversity. The results are in agreement with numerous reports on the major effect of abiotic conditions during development, maturation and ripening on fruit quality and chemistry (Crisosto et al., 1997; Ben-Arie et al., 1984; Badenes et al., 1998; Borochov-Neori and Shomer, 2001; Dumas et al., 2003; Toor et al., 2006; Raffo et al., 2006). The higher red color intensity of the arils at the beginning (early July) and the end (October) of the sampling period, compared to late-July through September, probably reflects the detrimental effect of high temperatures on anthocyanin accumulation (OrenShamir and Nissim-Levi, 1999); the extreme temperatures during
July and August in the southern Arava Valley (Fig. 1) may decrease anthocyanin content by slowing down synthesis (Shvarts et al., 1977) and accelerating degradation (Shaked-Sachary et al., 2002). Indeed, the intensity of the red color of the arils was found to be inversely related to the sum of heat units accumulated during fruit development and ripening (Fig. 4 and Table 1). Moreover, in preliminary experiments that employed shade nets to reduce air temperature in fruit vicinity during ripening, the red color intensity of the aril was enhanced in fruit of the early-CV that ripened during July and August (Tripler and Borochov-Neori, unpublished results). A comparable climate effect on the red color intensity of pomegranate fruit juice was demonstrated for the CV ‘Wonderful’ grown in two distinctly different climatic regions in Israel (Ben-Arie et al., 1984). A general trend of increase in aril TSS, soluble phenolics content and antioxidative capacity with the progression throughout the harvest season was established between August and the end of October. Taken together with the seasonal variations in aril red
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color intensity, pomegranate fruit from later harvest dates were of superior sensory and antioxidant value in the three CVs. Ripe pomegranate fruit of each of the 11 studied CVs had a distinct set of values of red color intensity of arils and juice TSS, pH, soluble phenolic concentration and antioxidative capacity (Table 2). The 11 sets of values enabled testing for correlations between the individual parameters (Fig. 6). The antioxidative capacity related linearly to the concentration of soluble phenolics (Fig. 6A), supporting the view that the latter are the major contributors to the high antioxidant activity measured in pomegranate juice (Gil et al., 2000; Poyrazoglu et al., 2002; Seeram et al., 2005; Li et al., 2006). The apparent specific antioxidant activity of the soluble phenolics in the juice was calculated from the slope of the linear regression curve (Fig. 6A) to be equivalent to 0.36 mole vitamin C per mole phenolic hydroxyl. Aril red color intensity did not relate to the pH of the extracted juice (Fig. 6D), indicating that the highly pH-sensitive anthocyanins remained segregated (Small and Pecket, 1982) in the separated arils. Thus, ‘‘a*’’ values in this study could serve as a valid estimate for anthocyanin concentration when comparing the different CVs. The disparity between the juice antioxidative capacity and aril red color intensity (Fig. 6B) indicates that the anthocyanins in the pomegranate juice are not major contributors to the overall antioxidative capacity exhibited by the juice. The result is consistent with the values reported by Gil et al. (2000) for the antioxidant activities of individual soluble phenolic compounds present in the pomegranate juice, including anthocyanins. Hence, the assumption that anthocyanins in pomegranate juice are of a uniquely high antioxidative power (Noda et al., 2002) requires further elucidation. 5. Conclusions The pomegranate fruit is highly valued for its health-promoting benefits. However, the carpometric characteristics of the fruit also play an important role in its consumption. While the healthrelated quality, i.e. antioxidative capacity, is mainly dependent on the soluble phenolics content, fruit attractiveness is primarily related to color and taste parameters of the arils and their juice. Consumer satisfaction and producer profitability require that the fruit excels in both aspects. The findings of this study that the health and attractiveness factors in the pomegranate fruit (1) are not directly correlated with one another and (2) vary with cultivar and season of fruit development and ripening, would be important to the current efforts to upgrade pomegranate fruit quality by breeding and agricultural practices. Cultivation approaches that influence the season of fruit production and include climate management during fruit development and ripening will enable growers to improve fruit sensory qualities and antioxidant value of preferred pomegranate cultivars. Acknowledgments The study was supported by the Jewish National Fund (KKL) and the Chief Scientist of the Israeli Ministry of Agriculture (Grant No. 650-0275-05). References Akay, F., Yildiz, F., Pfannhauser, W., Fenwick, G.R., Khokhar, S., 2001. Estimation of total antioxidant capacity of pomegranate, apricot, caper, eggplant and oils. Biologically active phytochemicals in food: analysis, metabolism, bioavailability and function. In: Pfannhauser, W., Fenwick, G.R. (Eds.), Proceedings of the EUROFOODCHEM XI Meeting, Norwich, UK, 26–28 September, pp. 368–370. Aviram, M., Dornfeld, L., 2001. Pomegranate juice consumption inhibits serum angiotensin converting enzyme activity and reduces systolic blood pressure. Atherosclerosis 158, 195–198.
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Evaluation of antioxidant properties of pomegranate peel extract in comparison with pomegranate pulp extract. Food Chem. 96, 254–260. Manach, C., Scalbert, A., Morand, C., Re´me´sy, C., Jime´nez, L., 2004. Polyphenols: food sources and bioavailability. Am. J. Clin. Nutr. 79, 727–747. Manach, C., Williamson, G., Morand, C., Scalbert, A., Re´me´sy, C., 2005. Bioavailability and bioefficacy of polyphenols in humans. I. Review of 97 bioavailability studies. Am. J. Clin. Nutr 81, 230S–242S. Noda, Y., Kaneyuki, T., Mori, A., Packer, L., 2002. Antioxidant activities of pomegranate fruit extract and its anthocyanidins: delphinidin, cyanidin, and pelargonidin. J. Agric. Food Chem. 50, 166–171. Oren-Shamir, M., Nissim-Levi, A., 1999. Temperature and gibberellin effect on growth and anthocyanins pigmentation in Photinia leaves. J. Hort. Sci. 74, 355–360. Perez-Vincente, A., Gil-Izquierdo, A., Garcia-Viguera, C., 2002. In vitro gastro-intestinal digestion study of pomegranate juice phenolic compounds, anthocyanins, and vitamin C. J. Agric. Food Chem. 50, 2308–2312. Poyrazoglu, E., Gokmen, V., Artik, N., 2002. Organic acids and phenolic compounds in pomegranates (Punica granatum L.) grown in Turkey. J. Food Comp. Anal. 15, 567–575. Raffo, A., La Malfa, G., Fogliano, V., Madani, G., Quaglia, G., 2006. Seasonal variations in antioxidant components of cherry tomatoes (Lycopersicon esculentum cv. Naomi F1). J. Food Comp. Anal. 19, 11–19. Scalbert, A., Williamson, G., 2000. Dietary intake and bioavailability of polyphenols. J. Nutr. 130, 2073s–2085s. Seeram, N.P., Adams, L.S., Henning, S.M., Niu, Y., Zhang, Y., Nair, M.G., Heber, D., 2005. In vitro antiproliferative, apoptotic and antioxidant activities of punicalagin, ellagic acid and total pomegranate tannin extract are enhanced in
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Contents lists available at ScienceDirect
Journal of Food Composition and Analysis journal homepage: www.elsevier.com/locate/jfca
Original Article
Seasonal and cultivar variations in antioxidant and sensory quality of pomegranate (Punica granatum L.) fruit Hamutal Borochov-Neori a,*, Sylvie Judeinstein a, Effi Tripler a, Moti Harari a, Amnon Greenberg a, Ilan Shomer b, Doron Holland c a b c
Southern Arava Research and Development, Hevel Eilot, 88820, Israel Agricultural Research Organization, Department of Food Science, The Volcani Center, P.O. Box 6, Bet Dagan, 50250, Israel Agricultural Research Organization, Department of Horticulture, Newe Ya’ar Research Center, P.O. Box 1021, Ramat Yishay, 30095, Israel
A R T I C L E I N F O
A B S T R A C T
Article history: Received 14 August 2007 Received in revised form 5 October 2008 Accepted 27 October 2008
Fruits of diverse pomegranate (Punica granatum L.) cultivars were analyzed for soluble phenolics content, antioxidant activity, soluble solid concentration, acidity and internal red color intensity. Analysis was carried out at various dates throughout the harvest season, corresponding to different climatic conditions during fruit ripening. Values obtained varied with cultivar and ripening date. In three cultivars of different sensory properties and harvest season, comparison between late- and earlyripening fruit revealed that arils of fruit ripening later in the season contained more soluble phenolics (1.21–1.71 compared to 0.22–0.88 pyrogallol equivalents, g L1) and exhibited a higher antioxidant activity, as measured by the ferric reducing ability (FRAP) assay (1.22–2.37 compared to 0.86–1.95 vitamin C equivalents, g L1). The red color intensity of the arils inversely related (R2 = 0.89–0.94) to the sum of heat units accumulated during fruit ripening. Multiple linear regression analysis on fruit characteristics in 11 diverse cultivars indicated that juice antioxidative capacity linearly correlated with soluble phenolics content (R2 = 0.98), but not with the red color intensity of the arils (R2 = 0.38). Also, no significant correlation was established between aril color and either juice pH or total soluble phenolics content. The results imply that pomegranate fruit antioxidant and sensory quality traits can be enhanced by the choice of cultivar and controlled-climate cultivation management. ß 2009 Elsevier Inc. All rights reserved.
Keywords: Pomegranate Punica granatum L. Anthocyanins Antioxidants Antioxidative capacity Cultivar Climatic conditions Fruit quality Phenolics Biodiversity and nutrition Food analysis Food composition
1. Introduction The pomegranate (Punica granatum L.) fruit is highly valued for its health-promoting effects in reducing the risk of cardiovascular and other chronic disorders. This claim is supported by the results of an increasing number of clinical studies in both humans and animals (Lee and Watson, 1998; Aviram et al., 2000, 2004; Aviram and Dornfeld, 2001; Kaplan et al., 2001; de Nigris et al., 2005) and in vitro experiments in tumor and macrophage cell cultures (KimNamDeuk et al., 2002; de Nigris et al., 2005; Fuhrman et al., 2005; Seeram et al., 2005). The beneficial health qualities have been attributed to the exceptionally high antioxidative capacity (AOC) of the fruit juice (Gil et al., 2000; Akay et al., 2001), seemingly the result of the remarkably high content and unique composition of soluble phenolic compounds (Gil et al., 2000; Poyrazoglu et al., 2002; Seeram et al., 2005). Phenolic concentration and composition in the pomegranate fruit are cultivar-dependent; the most
* Corresponding author. Tel.: +972 8 6355747; fax: +972 8 6355730. E-mail address: [email protected] (H. Borochov-Neori). 0889-1575/$ – see front matter ß 2009 Elsevier Inc. All rights reserved. doi:10.1016/j.jfca.2008.10.011
abundant components are anthocyanins, catechins, ellagic tannins, gallic and ellagic acids (El-Nemr et al., 1990; de Pascual-Teresa et al., 2000; Gil et al., 2000; Poyrazoglu et al., 2002). The in vivo and in vitro studies described in the scientific literature were conducted with pomegranate juice prepared from fruit of the more popular cultivars (CVs), typified by an intense internal red color. Thus, a special significance was proposed for the anthocyanins (Noda et al., 2002), the molecular red color origin of the fruit juice (Gil et al., 1995; Hernandez et al., 1999). It appears, however, that anthocyanin bioavailability is lower than that of other soluble polyphenolics, such as phenolic acids, isoflavones and catechins (Scalbert and Williamson, 2000; Perez-Vincente et al., 2002; Manach et al., 2004, 2005). To date, no comparative studies were reported on the health-promoting effects of pomegranate juice from cultivars of a less intense internal red color. In addition, the physical and chemical properties of the fruit are highly dependent on the season of development and ripening (Ben-Arie et al., 1984; Badenes et al., 1998; Borochov-Neori and Shomer, 2001; Dumas et al., 2003; Toor et al., 2006; Raffo et al., 2006). The reported in vivo and in vitro studies employed pomegranate juice prepared from commercial harvests, where
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cultivar, level of ripening, agricultural practices and harvest date reflect grower and producer preferences that do not necessarily match health-promoting objectives. To accurately assess the health value in pomegranate fruit and juice consumption, it is important to examine cultivar and seasonal variations in antioxidant content and activity. The present study aimed to develop knowledge on cultivar and seasonal differences in pomegranate fruit antioxidant and sensory quality traits. To achieve this objective, a diverse collection of pomegranate cultivars differing in fruit internal color (from white to deep red), taste (from sour to sweet) and ripening season (from early summer to late autumn) was examined on several ripening dates throughout the harvest season (mid-July to end of October); aril dimension and color as well as juice content, soluble phenolics concentration, antioxidative capacity, pH and total soluble solid (TSS) content were measured. The results were used to test for correlations between fruit antioxidant and sensory-related parameters and explore the role of climate factors. 2. Materials and methods Fresh ripe pomegranate (P. granatum L.) fruits were analyzed. The fruit were sampled from the pomegranate orchard at the Experimental Farm of the southern Arava R&D situated in the Israeli southern Arava Valley (latitude 298530 N; longitude 35830 E), which is characterized by desert climate (Fig. 1) and inferior water quality (electrical conductivity of 3.5 dS m1). The pomegranate plot accommodates trees of 11 cultivars originally from the collection of Assaf et al., Newe Ya’ar Research Center, ARO [registered in the Israel Gene Bank for Agricultural Crops (IGB, web site: http://igb.agri.gov.il)]. The manuscript summarizes studies conducted during 14 August–25 October 2002 and 12 July–25 October in 2004 and 2005, respectively. On each sampling date newly ripened fruit were selected by external criteria according to customary grower practices; the latter include external color, size and shape. The fruit were cooled and studied within 24 h. Each measurement was repeated on five fruits of a similar size from different trees and locations in the orchard, i.e. five replicates. Analytical assays were carried out in triplicates. Intact arils were separated from the pith and carpellary membranes by hand and ripeness was further assessed by tasting; only non-astringent, edible fruit were analyzed. The separated arils
were counted and weighed. Surface color measurements were performed on uniform 3-cm-thick layers of separated arils using a chromameter equipped with a glass light projection tube (CR-300 and CR-A33e, Minolta, Japan). The color was expressed in CIELAB coordinates, where positive ‘‘a*’’ and ‘‘b*’’ represent the red and yellow components, respectively, and ‘‘L*’’ conveys the luminosity dimension, ranging from 0 (pure black) to 100 (white, calibrated against the white reference plate provided with the chromameter). Juice was prepared from isolated arils by a solid fruit juice extractor (Juice Extractor, Model Le Duo, Magimix, France); it was then weighed and immediately analyzed. pH was measured using a specialized food electrode (pH 211 microprocessor pH meter and FC 200B food electrode, Hanna Instruments, Romania). TSS concentration in % was evaluated with a hand refractometer (ATAGO, ATC-1E, Brix 0–32%, Japan). Pomegranate juice was extracted (1:3, v/v) with 80% methanol supplemented with 2 mM NaF, centrifuged (10,000 rpm for 10 min at 4 8C, Sorvall Instruments RC5C) and the supernatant diluted 10-fold with double distilled water (DDW). Concentration of total soluble phenolics was measured colorimetrically with Folin-Ciocalteau 2N phenol reagent (SIGMA Chemical Co, USA) according to Singleton and Rossi (1965). Aliquots of 100 mL were added to 900 mL reaction solution consisting of 200 mL freshly prepared 10-fold diluted Folin-Ciocalteau reagent, 100 mL Na2CO3 and 600 mL DDW. Pyrogallol (SIGMA Chemical Co, USA) was used for the calibration curve (0–100 mg mL1). The absorbance at 765 nm was measured with a spectrophotometer (SHIMADZU Corporation, UV-1650PC, Kyoto, Japan) after 1-h incubation, and the results were expressed in pyrogallol equivalents. AOC was measured by the colorimetric test originally developed to assess the ferric reducing ability of plasma (FRAP) (Benzie and Straino, 1996); the assay was shown to be appropriate for AOC estimation in pomegranate juice (Gil et al., 2000). Clear methanolic extract was prepared as described earlier and diluted 10- to 20-fold with DDW. Fifty microliters were added to 950 mL freshly prepared FRAP working solution [50 mL 300 mM acetate buffer + 5 mL 10 mM 2,4,6-tripyridyl-s-triazine (TPTZ) + 5 mL 20 mM ferric chloride] in a 37 8C water bath. Absorbance at 593 nm was measured with a spectrophotometer (SHIMADZU Corporation, UV-1650PC, Kyoto, Japan) after 4 min. Vitamin C (Fluka, Switzerland) was used for the calibration curve (0–100 mg mL1), and the results were expressed in terms of vitamin C equivalents.
Fig. 1. Climatic data for the Israeli southern Arava Valley (latitude 298530 N; longitude 35830 E). The values are the long-term averages obtained from the local meteorological station during the years 1995–2005. (A) Maximal and minimal air temperature. (B) Maximal and minimal relative humidity (RH). (C) Daily evaporation. (D) Rainfall.
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Fruit physical parameters (juice content, weight and number of arils, and internal red color intensity) and aril juice TSS were determined during three harvest seasons (2002, 2004 and 2005). AOC, total soluble phenolics and pH measurements were conducted during the harvest seasons of 2004 and 2005. The experimental values for each sampling date are the average and standard deviation of measurements performed on five fruits from different trees and repeated for two or three harvest seasons. 3. Results 3.1. Fruit analysis throughout the harvest season Ripe pomegranate fruit of three CVs were studied on several dates throughout the harvest season in the years 2002, 2004 and 2005 (Figs. 2–5). The cultivars, identified here by Newe Ya’ar code system (IGB, web site: http://igb.agri.gov.il), represent three distinct types of the crop: P.G. 128-29 – internally red, sweet, early-ripening (early-CV); P.G. 119-20 – internally pink, sweet, early to mid-season ripening (mid-CV); P.G. 101-2 – internally red, sweet and sour, late-ripening (late-CV). The early-CV started yielding ripe fruits on July 12, the first sampling date. Fruits of the mid- and late-CVs reached ripeness approximately 1 and 2 months later, respectively. Once ripening began, newly ripened fruit were available on the selected sampling dates throughout the study period. In the early-CV, fruit juice content (Fig. 2) was considerably lower in early July and October compared to end of July to end of September. Also, with the progression in harvest season aril weight increased; concomitantly, the number of arils per fruit decreased.
Fig. 3. Aril color measurements throughout the harvest season in ripe fruit of three pomegranate CVs. (A) Late-CV (P.G. 101-2). (B) Mid-CV (P.G. 119-20). (C) Early-CV (P.G. 128-29). ‘‘L*’’, luminosity; ‘‘a*’’, red component; ‘‘b*’’, yellow component.
Unlike the early-CV, in the mid- and late-CVs, fruit juice content as well as aril weight and number (Fig. 2) did not significantly change during the entire sampling period. Fruit aril color varied throughout the season (Fig. 3). Red color intensity (a*) of arils from the early-CV decreased from July to September and increased
Fig. 2. Physical parameters throughout the harvest season of the edible portion of ripe pomegranate fruit in three CVs: P.G. 128-29 (early-CV, *), P.G. 119-20 (midCV, &), P.G. 101-2 (late-CV, D). (A) Number of arils per fruit. (B) Weight of a single aril. (C) Weight fraction of aril juice.
Fig. 4. Correlation analysis between red color intensity of the aril, ‘‘a*’’, and the sum of heat units accumulated during the last 6 weeks of fruit development and ripening. Lines are the best-fit curves obtained by linear (early-CV, P.G. 128-29) and reciprocal (late-CV, P.G. 101-2) regression analyses.
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Fig. 5. Chemical parameters throughout the harvest season of freshly extracted aril juice from ripe fruit of three pomegranate CVs: early-CV (P.G. 128-29, *), mid-CV (P.G. 119-20, &), late-CV (P.G. 101-2, D). (A) TSS; (B) pH; (C) Total soluble phenolics content; (D) AOC. The total soluble phenolics content and AOC are in g L1 pyrogallol and vitamin C equivalents, respectively.
on later sampling dates; the luminosity (L*) declined concurrently. Arils of the mid-CV were initially white and gradually changed to pink during October as reflected by the small increase in ‘‘a*’’ and decrease in ‘‘L*’’. In arils of the late-CV, ‘‘a*’’ developed slowly in September and more quickly in October, with ‘‘L*’’ decreasing concomitantly. The extent of internal red color development in relation to the local temperatures during fruit development and ripening was examined in the early- and late-CVs (Fig. 4). In ripe fruit arils, ‘‘a*’’ inversely related to the sum of heat units (Wang, 1960) accumulated during 6 weeks prior to harvest. In calculating the accumulated heat, daily heat units were defined as the difference, in Celsius degrees, between the daily average temperature and 25 8C. A heat unit value of zero was assigned when the average daily temperature was less than 25 8C. Regression analysis of the data gave best fit to inverse linear (R2 = 0.89) and reciprocal (R2 = 0.94) correlations for the early- and late-CV, respectively. Similar inverse correlations were obtained when shorter periods of heat accumulation were considered (Table 1). The chemical parameters of fresh juice extracted from the separated arils changed throughout the sampling season (Fig. 5). TSS (Fig. 5A) increased with the advancement in ripening date, reaching approximately 15.5% in the three CVs. Juice pH increased from 3.8 to 4.2 between July and August in the early-CV; in all three CVs the pH (Fig. 5B) was constant in fruit that ripened during August and September and decreased in fruit ripening in October. Highest and lowest pH values were measured in the early- and late-CVs, 3.8–4.2 and 3.2–3.4, respectively. The content of total soluble phenolics (Fig. 5C) slightly decreased in the early-CV between mid-July and mid-August (from 0.44 to 0.39 pyrogallol Table 1 Correlation analysis between red color intensity of arils, ‘‘a*’’, and heat unit accumulation during fruit development and ripening. Correlation coefficients (R2) derived from linear [early-CV (P.G. 128-29)] and reciprocal [late-CV (P.G. 101-2)] regression analyses are presented. Period of heat unit accumulation (weeks prior to harvest) 2 4 6
Correlation coefficient (R2) P.G. 128-29
P.G. 101-2
0.84 0.89 0.89
0.78 0.91 0.94
equivalents, g L1) and was significantly higher in fruits of all three CVs that ripened on later dates, reaching values in the range of 1.2–1.7 pyrogallol equivalents, g L1, depending on the CV. The antioxidative capacity (Fig. 5D) followed a similar trend with a decrease in the early-CV from mid-July to mid-August (from 1.95 to 1.54 vitamin C equivalents, g L1) and an increase later in the season for all three CVs, reaching values in the range of 1.2–2.4 vitamin C equivalents, g L1, depending on the CV. Both parameters (total phenolics and antioxidative capacity) were lower in the mid-CV compared to both the early- and late-CVs. 3.2. Interrelations between aril color and chemical parameters Eleven pomegranate CVs representing an extensive assortment of color and taste qualities as well as ripening season were studied (Table 2). Color measurements on separated arils and chemical analysis of the extracted juice were performed on freshly ripened fruit collected on the same date, i.e. exposed to similar climatic conditions during ripening. Each CV had a characteristic set of color and chemical values (Table 2). Every pair of parameters was tested by regression analysis for potential interrelationship (Fig. 6). The antioxidative capacity and total soluble phenolics content were linearly correlated (Fig. 6A; y = 1.52x 0.27, R2 = 0.98). Poor linear correlation was found for the antioxidative capacity as a function of the internal red color intensity (Fig. 6B; y = 0.05x + 1.09, R2 = 0.38). The intensity of the red color of the arils did not correlate with either the total soluble phenolics concentration (Fig. 6C) or the pH (Fig. 6D). 4. Discussion The growing number of scientific reports on the health benefits of the pomegranate fruits (Lee and Watson, 1998; Aviram et al., 2000, 2004; Aviram and Dornfeld, 2001; Kaplan et al., 2001; de Nigris et al., 2005) has generated a significant increase in consumer interest in and, consequently, agricultural production of the crop. To assure consumer satisfaction and producer profitability, it is particularly important to ensure both high content of health-promoting nutrients and fruit attractiveness for either fruit or juice consumption. In this context, the present study demonstrates that pomegranate antioxidant and sensory quality depend on cultivar and climatic conditions during fruit maturation and ripening.
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Table 2 Properties of ripe pomegranate fruit from 11 CVs grown in the Israeli southern Arava Valley. The values are the average standard deviation of measurements during two harvest seasons. CV (Newe Ya’ar code no.)
Ripening season
Aril taste
Aril color
Red color intensity (a*)
TSS (%)
pH
Total soluble phenolics (pyrogallol equivalents, g L1)
Antioxidative capacity (vitamin C equivalents, g L1)
P.G. P.G. P.G. P.G. P.G. P.G. P.G. P.G. P.G. P.G. P.G.
Mid Early Late Late Mid Mid Early Late Mid Mid Mid
Sweet Sweet Sour Sweet Sour Sour Sweet Sour Sweet Sweet Sweet
Light pink Dark red Bright red Pink Light pink Light pink Red Red Dark pink Pink Light pink
9.2 0.5 34.1 1.1 19.4 1.7 13.5 0.5 9.9 0.5 10.4 0.5 24.8 1.5 24.5 1.0 16.9 1.0 12.3 0.5 10.4 0.5
14.6 0.3 15.2 0.1 15.9 0.5 13.5 0.3 14.3 0.3 14.7 0.5 14.2 0.4 15.2 0.3 15.0 0.3 15.0 0.2 13.1 0.2
3.7 0.1 4.0 0.1 3.4 0.1 3.9 0.1 3.9 0.1 3.7 0.1 3.8 0.1 3.0 0.1 3.6 0.1 3.7 0.1 4.5 0.1
1.21 0.09 1.53 0.01 1.71 0.13 1.37 0.05 1.06 0.05 1.58 0.08 1.60 0.07 2.26 0.08 1.04 0.05 0.99 0.04 1.09 0.04
1.46 0.04 2.18 0.02 2.21 0.19 1.90 0.05 1.30 0.07 2.16 0.10 2.09 0.08 3.16 0.11 1.34 0.04 1.25 0.06 1.33 0.05
119-20 128-29 101-2 127-28 118-19 104-5 130-31 116-17 114-15 105-6 106-7
Fig. 6. Tests for correlations between pairs of ripe pomegranate fruit parameters: (A) antioxidative capacity (AOC) vs. total soluble phenolics content; (B) AOC vs. ‘‘a*’’ (aril red color intensity); (C) ‘‘a*’’ vs. total soluble phenolics content; (D) ‘‘a*’’ vs. juice pH. Each point in each figure presents 1 of 11 pomegranate CVs. AOC and total soluble phenolics content are in g L1 vitamin C and pyrogallol equivalents, respectively.
The different ripening dates examined throughout the harvest season signify distinct regimes of climatic conditions during fruit development and ripening. In three pomegranate cultivars differing in sensory qualities and ripening season, aril color as well as the pH, TSS, total soluble phenolics content and antioxidative capacity of the extracted juice varied with ripening date in a similar fashion and on a comparable time scale (when applicable) despite cultivar diversity. The results are in agreement with numerous reports on the major effect of abiotic conditions during development, maturation and ripening on fruit quality and chemistry (Crisosto et al., 1997; Ben-Arie et al., 1984; Badenes et al., 1998; Borochov-Neori and Shomer, 2001; Dumas et al., 2003; Toor et al., 2006; Raffo et al., 2006). The higher red color intensity of the arils at the beginning (early July) and the end (October) of the sampling period, compared to late-July through September, probably reflects the detrimental effect of high temperatures on anthocyanin accumulation (OrenShamir and Nissim-Levi, 1999); the extreme temperatures during
July and August in the southern Arava Valley (Fig. 1) may decrease anthocyanin content by slowing down synthesis (Shvarts et al., 1977) and accelerating degradation (Shaked-Sachary et al., 2002). Indeed, the intensity of the red color of the arils was found to be inversely related to the sum of heat units accumulated during fruit development and ripening (Fig. 4 and Table 1). Moreover, in preliminary experiments that employed shade nets to reduce air temperature in fruit vicinity during ripening, the red color intensity of the aril was enhanced in fruit of the early-CV that ripened during July and August (Tripler and Borochov-Neori, unpublished results). A comparable climate effect on the red color intensity of pomegranate fruit juice was demonstrated for the CV ‘Wonderful’ grown in two distinctly different climatic regions in Israel (Ben-Arie et al., 1984). A general trend of increase in aril TSS, soluble phenolics content and antioxidative capacity with the progression throughout the harvest season was established between August and the end of October. Taken together with the seasonal variations in aril red
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color intensity, pomegranate fruit from later harvest dates were of superior sensory and antioxidant value in the three CVs. Ripe pomegranate fruit of each of the 11 studied CVs had a distinct set of values of red color intensity of arils and juice TSS, pH, soluble phenolic concentration and antioxidative capacity (Table 2). The 11 sets of values enabled testing for correlations between the individual parameters (Fig. 6). The antioxidative capacity related linearly to the concentration of soluble phenolics (Fig. 6A), supporting the view that the latter are the major contributors to the high antioxidant activity measured in pomegranate juice (Gil et al., 2000; Poyrazoglu et al., 2002; Seeram et al., 2005; Li et al., 2006). The apparent specific antioxidant activity of the soluble phenolics in the juice was calculated from the slope of the linear regression curve (Fig. 6A) to be equivalent to 0.36 mole vitamin C per mole phenolic hydroxyl. Aril red color intensity did not relate to the pH of the extracted juice (Fig. 6D), indicating that the highly pH-sensitive anthocyanins remained segregated (Small and Pecket, 1982) in the separated arils. Thus, ‘‘a*’’ values in this study could serve as a valid estimate for anthocyanin concentration when comparing the different CVs. The disparity between the juice antioxidative capacity and aril red color intensity (Fig. 6B) indicates that the anthocyanins in the pomegranate juice are not major contributors to the overall antioxidative capacity exhibited by the juice. The result is consistent with the values reported by Gil et al. (2000) for the antioxidant activities of individual soluble phenolic compounds present in the pomegranate juice, including anthocyanins. Hence, the assumption that anthocyanins in pomegranate juice are of a uniquely high antioxidative power (Noda et al., 2002) requires further elucidation. 5. Conclusions The pomegranate fruit is highly valued for its health-promoting benefits. However, the carpometric characteristics of the fruit also play an important role in its consumption. While the healthrelated quality, i.e. antioxidative capacity, is mainly dependent on the soluble phenolics content, fruit attractiveness is primarily related to color and taste parameters of the arils and their juice. Consumer satisfaction and producer profitability require that the fruit excels in both aspects. The findings of this study that the health and attractiveness factors in the pomegranate fruit (1) are not directly correlated with one another and (2) vary with cultivar and season of fruit development and ripening, would be important to the current efforts to upgrade pomegranate fruit quality by breeding and agricultural practices. Cultivation approaches that influence the season of fruit production and include climate management during fruit development and ripening will enable growers to improve fruit sensory qualities and antioxidant value of preferred pomegranate cultivars. Acknowledgments The study was supported by the Jewish National Fund (KKL) and the Chief Scientist of the Israeli Ministry of Agriculture (Grant No. 650-0275-05). References Akay, F., Yildiz, F., Pfannhauser, W., Fenwick, G.R., Khokhar, S., 2001. Estimation of total antioxidant capacity of pomegranate, apricot, caper, eggplant and oils. Biologically active phytochemicals in food: analysis, metabolism, bioavailability and function. In: Pfannhauser, W., Fenwick, G.R. (Eds.), Proceedings of the EUROFOODCHEM XI Meeting, Norwich, UK, 26–28 September, pp. 368–370. Aviram, M., Dornfeld, L., 2001. Pomegranate juice consumption inhibits serum angiotensin converting enzyme activity and reduces systolic blood pressure. Atherosclerosis 158, 195–198.
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