- Email: [email protected]
Deconstructing a Fruit Serving: Comparing the Antioxidant Density of Select Whole Fruit and 100% Fruit Juices
RESEARCH Research and Professional Briefs
Deconstructing a Fruit Serving: Comparing the Antioxidant Density of Select Whole Fruit and 100% Fruit Juices Kristi Michele Crowe, PhD, RD, LD; Elizabeth Murray ARTICLE INFORMATION
ABSTRACT
Article history:
Research suggests phytonutrients, specifically phenolic compounds, within fruit may be responsible for the putatively positive antioxidant benefits derived from fruit. Given the prominence of fruit juice in the American diet, the purpose of this research was to assess the antioxidant density of fresh fruit and 100% fruit juice for five commonly consumed fruits and juices and to compare the adequacy of 100% juice as a dietary equivalent to whole fruit in providing beneficial antioxidants. Antioxidant density was measured using an oxygen radical absorbance capacity method on six samples assayed in triplicate for each fruit (grape, apple, orange, grapefruit, pineapple), name-brand 100% juice, and store-brand 100% juice. One-way analysis of variance and Tukey’s honestly significant difference or Student t test were used to assess significance (P<0.05). Antioxidant density (mmol TE/100 g) of apple, orange, and grapefruit was 23% to 54% higher than the mean antioxidant density of name-brand and store-brand juices for each fruit; however, only apple and grapefruit exhibited significantly greater (P<0.05) antioxidant density than either of their name-brand or store-brand juices. In contrast, the mean antioxidant density of name-brand grape and pineapple juice was higher than fresh grape or pineapple fruit; however, both fresh grapes and commercial grape juice contained significantly more (P<0.05) antioxidants than store-brand grape juice. Regardless of the convenience of fruit juice, results support the recommendations of the 2010 Dietary Guidelines for Americans for increasing fruit servings in the whole fruit form due to their provision of beneficial antioxidants and fiber with approximately 35% less sugar.
Accepted 22 April 2013 Available online 26 June 2013
Keywords: Fruit Juice Antioxidant density Phytonutrients Oxygen radical absorbance capacity (ORAC) Copyright ª 2013 by the Academy of Nutrition and Dietetics. 2212-2672/$36.00 http://dx.doi.org/10.1016/j.jand.2013.04.024
J Acad Nutr Diet. 2013;113:1354-1358.
I
NCREASED DIETARY INTAKE OF FRUITS AND vegetables is associated with a decreased risk of chronic diseases such as diabetes, cardiovascular disease, hypertension, obesity, and some cancers.1 Many of the health benefits of fruits and vegetables are attributed to the phytonutrients or bioactive compounds within plants that provide health benefits beyond that of traditional nutrients.2 For example, research suggests that ascorbic acid, the active form of vitamin C, may contribute far less to the overall antioxidant capacity of fruit than phenolic compounds, a prominent class of phytonutrients. 3 Among many beneficial properties, phytonutrients contribute direct and indirect bioactivity attributable to their free radical scavenging ability such that these compounds are effective antioxidants involved in reducing low-density lipoprotein oxidation, decreasing Alzheimer’s disease risk, enhancing memory, and decreasing cancer cell proliferation. 4,5 In addition, increased dietary intake of phytonutrients has been shown to decrease serum biomarkers of inflammation and oxidative stress while increasing serum antioxidant levels.6-8 Based on the growing body of evidence related to increased fruit and vegetable consumption and decreased risks for 1354
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various chronic diseases, the US Department of Agriculture 2010 Dietary Guidelines for Americans (DGA) recommend increasing the amount of whole fruits and vegetables eaten daily such that half the plate is composed of these plant foods.9,10 According to the DGA, a serving of fruit is defined as 1 cup fruit, 1 cup 100% fruit juice, or 1/2 cup dried fruit.10 Due to consumer demand for prepackaged, shelf-stable food products, fruit juice is a convenient serving alternative to whole fruit in the eyes of many consumers. As a result, readyto-drink beverages, including those with claims that it “contains a whole serving of fruit or vegetables” have become one of the fastest growing food categories on the market.11 Although increased consumption of fruit juice has been noted in many population groups during the past decade, this growth has been particularly evident among children. According to data collected as part of the National Health and Nutrition Examination Survey, beverage consumption in children up to age 5 years noted a rapid increase in juice consumption from 2001 to 2006 compared with National Health and Nutrition Examination Survey data before 1980.12 Among this population, fruit juice was an important contributor of daily vitamins and minerals. Despite the ª 2013 by the Academy of Nutrition and Dietetics.
RESEARCH convenience of juice, it contains an increased amount of sugar and, typically, no fiber. Beyond these known differences, minimal research has been conducted to evaluate the more subtle differences, specifically antioxidant density, between a single serving of whole fruit and 100% fruit juice that may result from changes in food form; that is, fruit to juice. Among the more likely factors, which would be expected to influence the antioxidant density between the two fruit serving forms, is the removal of fruit peel and pulp containing high levels of phytonutrients, particularly phenolic compounds.13 For example, in the processing of strawberries to a variety of different food products, significant reductions in the total phenolic content and the total anthocyanin content were observed as a result of fruit mashing and heat treatment.14 Additional factors that would be expected to affect the antioxidant density of the two serving forms of fruit include the environment in which fruits are grown, fruit cultivar or varietal consumed or used to produce fruit juice, the plant growth cycle or ripening stage in which fruits are harvested, as well as the plant part/s incorporated in the juicing process.15,16 For example, phytonutrients are found in varying amounts throughout the fruit body and have a richer presence in the peel of most fruits.16 Likewise, white grape juice processed without the heating of grape skins has a significantly lower phytonutrient profile than purple grape juice, which is processed with the skin.15 Lastly, the antioxidant density of a serving of fresh fruit or 100% juice would be expected to differ due to the fact that many antioxidant vitamins and phytonutrients such as phenolic compounds are particularly heat labile such that high temperatures can alter the molecular structure and the resulting functionality.17 At present, the primary processing method for ensuring the safety of ready-to-drink juice is heat pasteurization, which relies on temperatures ranging from 161 F to 302 F (71 F to 150 C) depending on the type of pasteurization technique employed. Given the prominence of fruit juice in the American diet, the purpose of this research was to assess the antioxidant density of a single serving of select whole fruit and its 100% juice form for five commonly consumed fruits and juices. The antioxidant density of fresh grapes, apples, oranges, pineapple, and grapefruit were evaluated along with commercially available 100% juices of each fruit.
MATERIALS AND METHODS Chemicals and Equipment 6-Hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox; Hoffman-La Roche) and fluorescein (FL) were obtained from Aldrich. Reagent grade methanol and 2,2-azobis (2-amidino-propane) dihydrochloride (AAPH) were purchased from VWR International, Inc. Antioxidant capacity testing was performed using the FLUOstar Optima plate reader (BMG Labtech) equipped with 96 well FLUOTRAC 200 black microplates (VWR International, Inc).
Fruit and Commercial Fruit Juice Samples Fresh fruit along with bottled, shelf-stable name-brand and store-brand 100% fruit juices were obtained during the summer months from two regional grocery chains and one October 2013 Volume 113 Number 10
national superstore chain located in Tuscaloosa, AL. Fresh fruit selected for inclusion in this study included black seedless grapes (Vitis vinifera), navel oranges (Citrus sinesis), pineapple (Ananus sativus), Golden Delicious and Red Delicious apples (Malus domistica), and pink grapefruit (Citrus paradisi).
Sample Preparation Six samples of each fruit were analyzed in triplicate for the assessment of antioxidant density. Samples weighing 5 g edible portion that included the peel and skin on apples and grapes only were homogenized in 15 mL 80% methanol for 2 minutes using a VDI25 Homogenizer (VWR International, Inc) equipped with a large bore dispersion tool. The homogenate was centrifuged at 4,000g for 10 minutes at 5 C. The supernatant was transferred to a flask and the pelletized pulp was further extracted in pure acetone (1:2 weight per volume) to extract amphiphilic antioxidants within fruit pulp.18 After centrifugation under the above conditions, the extracts were used in the oxygen radical absorbance capacity (ORACFL) assay after suitable dilution with phosphate buffer (75 mmol/L sodium phosphate, pH 7.0). To assess the antioxidant density of fruit juice, six samples of each name-brand and store-brand juice were analyzed in triplicate using the ORACFL assay. All samples were diluted directly without further sample preparation using phosphate buffer (75 mmol/L sodium phosphate, pH 7.0) before antioxidant analysis.
Automated ORACFL Assay The ORACFL assay was carried out using the FLUOstar Optima plate reader equipped with an incubator and two injection pumps according to a previously validated and published method by Prior and colleagues.19 AAPH was used as the peroxyl radical generator and Trolox, a water-soluble analogue of vitamin E, served as the standard. Calibration curves of the standard ranging from 6.25 to 50 mmol/L Trolox were prepared fresh for each assay run. The decrease in fluorescence of fluorescein was determined by measuring excitation at 535 nm and emission at 595 nm to exhibit a fluorescence decay curve based on the antioxidant content of the sample. The final ORACFL values were calculated as the area under the fluorescence decay curve (AUC) according to the following equation: (AUCsampleeAUCbuffer)/ (AUCTroloxeAUCbuffer)dilution factor of sampleinitial Trolox concentration (in millimoles). Antioxidant density results are expressed as millimoles Trolox equivalents (TE)/100 g or millimoles TE/serving.
Statistical Analysis Antioxidant density was reported on a wet weight basis as the meanstandard deviation of all samples analyzed in triplicate. Data for four of the five tested fruits and juices (apple, grape, orange, and grapefruit) were subjected to oneway analysis of variance and Tukey’s honestly significant difference procedure to assess significant differences (P<0.05) in antioxidant density among whole fruit, namebrand 100% juice, and store-brand 100% juice. Because store-brand 100% pineapple juice was not available in any of the retail outlets, data from pineapple fruit and name-brand JOURNAL OF THE ACADEMY OF NUTRITION AND DIETETICS
1355
RESEARCH pineapple juice were subjected to a Student t test to assess significant differences (P<0.05) in antioxidant density. Statistical analysis was performed using Systat Analytical Software, version 11.0 (2012, Cranes Software International Inc). Percent reductions in antioxidant density were calculated based on the antioxidant density of whole fruit and the mean antioxidant density of both name-brand and store-brand juices combined.
RESULTS AND DISCUSSION Significant differences (P<0.05) in antioxidant density were observed between fruit and fruit juices as well as between name-brand and store-brand 100% juices. Statistical results based on mean ORAC values (mmol TE/100 g) for fresh fruit and fruit juice are depicted in the Figure. The antioxidant density of fresh apple, orange, and grapefruit was 54%, 23%, and 52% higher, respectively, compared with the mean antioxidant density of both 100% juices for each fruit. Despite these antioxidant losses, only fresh apple and grapefruit exhibited a significantly greater (P<0.05) antioxidant content than either name-brand or store-brand juices. These differences may be attributable to steps required in the production of fruit juice, including specific steps aimed at removing certain phenolic compounds, mainly flavonoids, which commonly undergo browning reactions and contribute to haze formation in processed juice.17 As a result of these steps and the removal of fruit pulp and peel before juice processing, many juices exhibit lower antioxidant density than their whole fruit counterparts. The antioxidant density (mmol TE/100 g) of grapes and name-brand grape juice did not differ significantly (P<0.05), yet both were significantly higher (P¼0.004) than storebrand 100% grape juice. Similarly, ORAC values for 100% pineapple juice were 56% higher than for pineapple fruit. These quantitative differences may be the result of the
ascorbic acid that is added to juice blends for both increasing the nutrient content of the juice and providing shelf-life extension by delaying oxidation reactions. Likewise, differences in antioxidant density between name-brand and storebrand juices may be reflective of potential dissimilarities in processing techniques employed or in differing fruit cultivars or varietals used among juice processors. Per-serving differences in antioxidant density (mmol TE/serving) are reported in the Table for all fruits and juices. The calculations were based on the weight in grams of a serving of each fruit as reported in the US Department of Agriculture National Nutrient Database for Standard Reference Release 25.20 A serving of fresh apple and grapefruit provides approximately 50% more antioxidants than a serving of 100% juice from either fruit. On a per-serving basis, 100% grape juice is superior in its antioxidant provision to a serving of fresh grapes. This is likely attributable to the weight differential between a 1-cup serving of fresh grapes (92 g) and a 1-cup serving of 100% grape juice (240 g). Likewise, based on the serving weight differential between a serving of fresh pineapple (165 g) and a serving of pineapple juice (240 g), the antioxidant provision of pineapple juice is superior to a serving of the whole fruit. It should also be emphasized that both name-brand and storebrand juices of each fruit were processed to contain 120% Daily Value of vitamin C in one serving. As such, this may have also contributed to the greater antioxidant density of grape and pineapple juice compared with their fresh fruit forms. Overall, a serving of each fruit contains 90 kcal and between 35% and 61% less sugar than a juice serving, which provides approximately 110 kcal and 17 g sugar. Despite the inconclusive, yet controversial link between intake of sugar-sweetened beverages and the obesity epidemic, research continues to investigate the potential role of greater consumption of sugar-sweetened beverages and
Figure. Antioxidant density (mmol Trolox [Hoffman-LaRoche]/equivalents/100 g) of select whole fruit and 100% fruit juices. Columns sharing letters are not significantly different (P>0.05) based on one-way analysis of variance and Tukey’s honestly significant difference test. 1356
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October 2013 Volume 113 Number 10
RESEARCH Table. Per-serving differences in antioxidant density of select whole fruit and 100% fruit juices
Fruit Grape
Sample type
Orange
Grapefruit
Pineapple
Mean TEa (mmol/100 g–SDb)
Weight (g) of 1 c servingc
TE mmol/serving
Fruit
6
213.7327.13
92
194.64
Name-brand juice
3
225.3142.43
240
540.75
Store-brand juice Apple
No. of units tested
3
119.7520.60
240
287.40
12d
403.47144.76
125
504.34
Name-brand juice
3
96.2220.15
240
230.93
Store-brand juice
3
99.8532.47
240
239.65
Fruit
Fruit
6
357.87133.67
165
590.49
Name-brand juice
3
194.3881.99
240
466.52
Store-brand juice
3
186.6982.51
240
448.08
Fruit
6
536.80122.67
230
1234.65
Name-brand juice
3
224.3954.02
240
538.65
Store-brand juice
3
270.994.40
240
650.40
Fruit
6
81.8115.28
165
135.00
125.6383.26
240
301.52
Name-brand juice
6
e
a
TE¼Trolox (Hoffman-LaRoche) equivalents. SD¼standard deviation. c Serving size based on gram weight of 1 cup fresh, raw fruit and serving of 100% juice from Nutrient Database for Standard Reference Release 25.20 d Twelve samples composed of 2 common apple varieties used in juice production (6 samples of each). e Six name-brand juices tested due to lack of availability of store-brand juices. b
increases in body weight.21,22 In addition, although the liquid energy provided by juice is metabolized in the same manner as the energy from solid fruit, the medium (solid or liquid) by which the fruit is consumed has been shown to play a significant role in providing satiety cues.23 Taken collectively, a serving of whole fruit, in most cases, remains the most nutritionally superior form for acquiring beneficial nutrients and phytonutrient-based antioxidants while also providing strong appetitive and compensatory dietary cues. Research such as this assists in moving nutrition science forward by evaluating the antioxidant density of both serving forms of fruit using an assay that measures the total capacity of all antioxidants rather than single antioxidants in fruit. By measuring the overall capacity, the antioxidant density measurements quantitatively represent the synergistic interactions of chain-breaking antioxidants working in concert to quench free radicals and regenerate other antioxidants in food systems and in biological samples.24-26 As a result, these synergistic interactions often provide greater capacity for sustained antioxidant effect than individual antioxidants alone. It is through the use of biologically relevant, total capacity assays that the effect of antioxidants in food systems have been shown to positively influence serum/plasma antioxidant capacity.4,27,28 Nevertheless, it should be pointed out that most compounds with antioxidant functionality, whether vitamin- or phytonutrient-based, perform additional roles in human health beyond their free radicalscavenging ability. The most notable limitation of the study is the inability to determine whether the fruits evaluated were from the same October 2013 Volume 113 Number 10
growing region as fruits used in production of tested juices because environmental conditions during plant growth would be expected to modify the macronutrient, micronutrient, and phytonutrient profile of individual commodities. In addition, a combination of fruit cultivars or varietals may have been used to produce the tested juices, whereas individual whole fruit represents only a single fruit cultivar. In all but two fruits, the antioxidant density of a single fruit cultivar was superior to that of its 100% juice form. To effectively limit these potential confounders, a robust sampling of each fruit and each juice were purchased from two regional grocery chains and one national superstore chain and analyzed in triplicate. It should be stated that the study was conducted to evaluate the antioxidant density of the point-of-sale fruit forms available to consumers. Thus, results of the study reflect an accurate quantitative assessment of the antioxidant density of fruit servings available in consumer markets at any given time point.
CONCLUSIONS Although 100% fruit juice can be part of a nutritious diet, research such as this underscores the DGA, which recommend the majority of fruit intake come from whole fruits due to the inverse relationship between consumption of fruit and vegetables and risk of chronic disease.9 Based on these research findings and recommendations within the DGA, whole fruit remains the preferred form over fruit juice for delivering beneficial antioxidants and fiber while also providing significantly less sugar per serving. JOURNAL OF THE ACADEMY OF NUTRITION AND DIETETICS
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RESEARCH References
16.
Marinova D, Ribarova F, Atanassova M. Total phenolics and total flavanoids in Bulgarian fruit and vegetables. J Univ Chem Technol Metall. 2005;40(3):255-260.
17.
Manach C, Scalbert A, Morand C, Rémésy C, Jiménez L. Polyphenols: Food sources and bioavailability. Am J Clin Nutr. 2004;79(5):727-747.
18.
Gorenstein S, Zachwieja Z, Katrich E, et al. Comparison of the contents of the main antioxidant compounds and the antioxidant activity of white grapefruit and its new hybrid. LWT Food Sci Technol. 2004;37(3):337-343.
Scalzo J, Al Politi, Pellegrini N, et al. Plant genotype affects total antioxidant capacity and phenolic contents in fruit. Nutr. 2005;21(2): 207-213.
19.
Garcia Alonso J, Ros G, Vidal-Guevara ML, Periago MJ. Acute intake of phenolic-rich juice improves antioxidant status in healthy subjects. Nutr Res. 2006;26(7):330-339.
Prior RL, Hoang H, Gu L, et al. Assays for hydrophilic and lipophilic antioxidant capacity (oxygen radical absorbance capacity [ORACFL]) of plasma and other biological and food samples. J Agric Food Chem. 2003;51(11):3273-3279.
20.
US Department of Agriculture, Agricultural Research Service. USDA National Nutrient Database for Standard Reference, Release 25. http://www.ars.usda.gov/ba/bhnrc/ndl. Updated October 9, 2012. Accessed October 17, 2012.
21.
Mattes RD, Shikany JM, Kaiser KA, Allison DB. Nutritively sweetened beverage consumption and body weight: A systematic review and meta-analysis of randomized experiments. Obesity Rev. 2010;12(5): 346-365.
22.
Malik V, Shulze M, Hu F. Intake of sugar-sweetened beverages and weight gain: A systematic review. Am J Clin Nutr. 2006;84(2):274-288.
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Boeing H, Bechthold A, Bub A, et al. Critical review: Vegetables and fruit in the prevention of chronic diseases. Eur J Nutr. 2012;51(6): 637-663.
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Lee J, Koo N, Min DB. Reactive oxygen species, aging, and antioxidative nutraceuticals. Compr Rev Food Sci Food Saf. 2003;3(1): 21-33.
3.
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Jia N, Xiong Y, Kong B, Lui Q, Xia X. Radical scavenging activity of black currant (Ribes nigrum L.) extract and its inhibitory effect on gastric cancer cell proliferation via induction of apoptosis. J Funct Foods. 2012;4(1):382-390.
6.
King GL. The role of inflammatory cytokines in diabetes and its complications. J Periodontol. 2008;79(8):1527-1534.
7.
Calder PC, Albers R, Antoine JM, et al. Inflammatory disease processes and interactions with nutrition. Br J Nutr. 2009;101(suppl 1): S1-S45.
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8.
Nemzer BV, Rodriguez LC, Hammond L, Disilvestro R, Hunter JM, Pietrzkowski Z. Acute reduction of serum 8-iso-PGF2-alpha and advanced oxidation protein products in vivo by a polyphenol-rich beverage; a pilot clinical study with phytochemical and in vitro antioxidant characterization. Nutr J. 2011;10(1):67-75.
Mattes RD, Campbell WW. Effects of food form and timing of ingestion on appetite and energy intake in lean young adults and in young adults with obesity. J Am Diet Assoc. 2009;109(3):430-437.
24.
Kotikova Z, Lachman J, Al Hejtmankova, et al. Determination of antioxidant activity and antioxidant content in tomato varieties and evaluation of mutual interactions between antioxidants. LWT Food Sci Technol. 2011;44(8):1703-1710.
9.
Nutrition and Your Health: Dietary Guidelines for Americans, 2010. http://www.dietaryguidelines.gov. Accessed October 17, 2012.
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How to count fruit servings. http://www.choosemyplate.gov/foodgroups/fruits-counts.html. Accessed November 27, 2012.
Yeum K, Beretta G, Krinsky N, Aldini G. Synergistic interactions of antioxidant nutrients in a biological model system. Nutrition. 2009;25(7-8):839-846.
26.
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Sloan E. What, when, and where America eats. Food Technol. 2012;66(1):21-32.
Yeum K, Russell R, Krinsky N, et al. Biomarkers of antioxidant capacity in the hydrophilic and lipophilic compartments of human plasma. Arch Biochem Biophys. 2004;430(4):97-103.
12.
Fulgoni V, Quann E. National trends in beverage consumption in children from birth to 5 years: Analysis of NHANES across three decades. Nutr J. 2012;11(1):92.
27.
Di Renzo L, Di Pierro D, Bigioni M, et al. Is antioxidant plasma status in humans a consequence of the antioxidant food content influence? Eur Rev Med Pharm Sci. 2007;11(3):185-192.
13.
Manthey J, Perkins-Veazie P. Influences of harvest date and location on the levels of b-carotene, ascorbic acid, total phenols, the in vitro antioxidant capacity, and phenolic profiles of five commercial varieties of mango (Mangifera indica L.). J Agric Food Chem. 2009;57(22): 10825-10830.
28.
Gheldof N, Xiao-HongW Engeseth NJ. Buckwheat honey increases serum antioxidant capacity in humans. J Agric Food Chem. 2003;51(5):1500-1505.
14.
Klopotek Y, Otto K, Bohm V. Processing strawberries to different products alters contents of vitamin C, total phenolics, total anthocyanins, and antioxidant capacity. J Agric Food Chem. 2005;53(14): 5640-5646.
15.
Dani C, Oliboni L, Vanderlinde R, Bonatto D, Salvador M, Henriques J. Phenolic content and antioxidant activity of white and purple juices manufactured with organically or conventionally produced grapes. Food Chem Toxicol. 2007;45(12):2574-2580.
AUTHOR INFORMATION K. M. Crowe is an assistant professor and E. Murray is a master’s student, Department of Human Nutrition, University of Alabama, Tuscaloosa. Address correspondence to: Kristi Michele Crowe, PhD, RD, LD, Department of Human Nutrition, Russell Hall Box 870311, University of Alabama, Tuscaloosa, AL 35487. E-mail: [email protected]
STATEMENT OF POTENTIAL CONFLICT OF INTEREST No potential conflict of interest was reported by the authors.
FUNDING/SUPPORT Funding for research supplies utilized in this research was made possible by the University of Alabama Crenshaw Endowed Research Fund.
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JOURNAL OF THE ACADEMY OF NUTRITION AND DIETETICS
October 2013 Volume 113 Number 10
Deconstructing a Fruit Serving: Comparing the Antioxidant Density of Select Whole Fruit and 100% Fruit Juices Kristi Michele Crowe, PhD, RD, LD; Elizabeth Murray ARTICLE INFORMATION
ABSTRACT
Article history:
Research suggests phytonutrients, specifically phenolic compounds, within fruit may be responsible for the putatively positive antioxidant benefits derived from fruit. Given the prominence of fruit juice in the American diet, the purpose of this research was to assess the antioxidant density of fresh fruit and 100% fruit juice for five commonly consumed fruits and juices and to compare the adequacy of 100% juice as a dietary equivalent to whole fruit in providing beneficial antioxidants. Antioxidant density was measured using an oxygen radical absorbance capacity method on six samples assayed in triplicate for each fruit (grape, apple, orange, grapefruit, pineapple), name-brand 100% juice, and store-brand 100% juice. One-way analysis of variance and Tukey’s honestly significant difference or Student t test were used to assess significance (P<0.05). Antioxidant density (mmol TE/100 g) of apple, orange, and grapefruit was 23% to 54% higher than the mean antioxidant density of name-brand and store-brand juices for each fruit; however, only apple and grapefruit exhibited significantly greater (P<0.05) antioxidant density than either of their name-brand or store-brand juices. In contrast, the mean antioxidant density of name-brand grape and pineapple juice was higher than fresh grape or pineapple fruit; however, both fresh grapes and commercial grape juice contained significantly more (P<0.05) antioxidants than store-brand grape juice. Regardless of the convenience of fruit juice, results support the recommendations of the 2010 Dietary Guidelines for Americans for increasing fruit servings in the whole fruit form due to their provision of beneficial antioxidants and fiber with approximately 35% less sugar.
Accepted 22 April 2013 Available online 26 June 2013
Keywords: Fruit Juice Antioxidant density Phytonutrients Oxygen radical absorbance capacity (ORAC) Copyright ª 2013 by the Academy of Nutrition and Dietetics. 2212-2672/$36.00 http://dx.doi.org/10.1016/j.jand.2013.04.024
J Acad Nutr Diet. 2013;113:1354-1358.
I
NCREASED DIETARY INTAKE OF FRUITS AND vegetables is associated with a decreased risk of chronic diseases such as diabetes, cardiovascular disease, hypertension, obesity, and some cancers.1 Many of the health benefits of fruits and vegetables are attributed to the phytonutrients or bioactive compounds within plants that provide health benefits beyond that of traditional nutrients.2 For example, research suggests that ascorbic acid, the active form of vitamin C, may contribute far less to the overall antioxidant capacity of fruit than phenolic compounds, a prominent class of phytonutrients. 3 Among many beneficial properties, phytonutrients contribute direct and indirect bioactivity attributable to their free radical scavenging ability such that these compounds are effective antioxidants involved in reducing low-density lipoprotein oxidation, decreasing Alzheimer’s disease risk, enhancing memory, and decreasing cancer cell proliferation. 4,5 In addition, increased dietary intake of phytonutrients has been shown to decrease serum biomarkers of inflammation and oxidative stress while increasing serum antioxidant levels.6-8 Based on the growing body of evidence related to increased fruit and vegetable consumption and decreased risks for 1354
JOURNAL OF THE ACADEMY OF NUTRITION AND DIETETICS
various chronic diseases, the US Department of Agriculture 2010 Dietary Guidelines for Americans (DGA) recommend increasing the amount of whole fruits and vegetables eaten daily such that half the plate is composed of these plant foods.9,10 According to the DGA, a serving of fruit is defined as 1 cup fruit, 1 cup 100% fruit juice, or 1/2 cup dried fruit.10 Due to consumer demand for prepackaged, shelf-stable food products, fruit juice is a convenient serving alternative to whole fruit in the eyes of many consumers. As a result, readyto-drink beverages, including those with claims that it “contains a whole serving of fruit or vegetables” have become one of the fastest growing food categories on the market.11 Although increased consumption of fruit juice has been noted in many population groups during the past decade, this growth has been particularly evident among children. According to data collected as part of the National Health and Nutrition Examination Survey, beverage consumption in children up to age 5 years noted a rapid increase in juice consumption from 2001 to 2006 compared with National Health and Nutrition Examination Survey data before 1980.12 Among this population, fruit juice was an important contributor of daily vitamins and minerals. Despite the ª 2013 by the Academy of Nutrition and Dietetics.
RESEARCH convenience of juice, it contains an increased amount of sugar and, typically, no fiber. Beyond these known differences, minimal research has been conducted to evaluate the more subtle differences, specifically antioxidant density, between a single serving of whole fruit and 100% fruit juice that may result from changes in food form; that is, fruit to juice. Among the more likely factors, which would be expected to influence the antioxidant density between the two fruit serving forms, is the removal of fruit peel and pulp containing high levels of phytonutrients, particularly phenolic compounds.13 For example, in the processing of strawberries to a variety of different food products, significant reductions in the total phenolic content and the total anthocyanin content were observed as a result of fruit mashing and heat treatment.14 Additional factors that would be expected to affect the antioxidant density of the two serving forms of fruit include the environment in which fruits are grown, fruit cultivar or varietal consumed or used to produce fruit juice, the plant growth cycle or ripening stage in which fruits are harvested, as well as the plant part/s incorporated in the juicing process.15,16 For example, phytonutrients are found in varying amounts throughout the fruit body and have a richer presence in the peel of most fruits.16 Likewise, white grape juice processed without the heating of grape skins has a significantly lower phytonutrient profile than purple grape juice, which is processed with the skin.15 Lastly, the antioxidant density of a serving of fresh fruit or 100% juice would be expected to differ due to the fact that many antioxidant vitamins and phytonutrients such as phenolic compounds are particularly heat labile such that high temperatures can alter the molecular structure and the resulting functionality.17 At present, the primary processing method for ensuring the safety of ready-to-drink juice is heat pasteurization, which relies on temperatures ranging from 161 F to 302 F (71 F to 150 C) depending on the type of pasteurization technique employed. Given the prominence of fruit juice in the American diet, the purpose of this research was to assess the antioxidant density of a single serving of select whole fruit and its 100% juice form for five commonly consumed fruits and juices. The antioxidant density of fresh grapes, apples, oranges, pineapple, and grapefruit were evaluated along with commercially available 100% juices of each fruit.
MATERIALS AND METHODS Chemicals and Equipment 6-Hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox; Hoffman-La Roche) and fluorescein (FL) were obtained from Aldrich. Reagent grade methanol and 2,2-azobis (2-amidino-propane) dihydrochloride (AAPH) were purchased from VWR International, Inc. Antioxidant capacity testing was performed using the FLUOstar Optima plate reader (BMG Labtech) equipped with 96 well FLUOTRAC 200 black microplates (VWR International, Inc).
Fruit and Commercial Fruit Juice Samples Fresh fruit along with bottled, shelf-stable name-brand and store-brand 100% fruit juices were obtained during the summer months from two regional grocery chains and one October 2013 Volume 113 Number 10
national superstore chain located in Tuscaloosa, AL. Fresh fruit selected for inclusion in this study included black seedless grapes (Vitis vinifera), navel oranges (Citrus sinesis), pineapple (Ananus sativus), Golden Delicious and Red Delicious apples (Malus domistica), and pink grapefruit (Citrus paradisi).
Sample Preparation Six samples of each fruit were analyzed in triplicate for the assessment of antioxidant density. Samples weighing 5 g edible portion that included the peel and skin on apples and grapes only were homogenized in 15 mL 80% methanol for 2 minutes using a VDI25 Homogenizer (VWR International, Inc) equipped with a large bore dispersion tool. The homogenate was centrifuged at 4,000g for 10 minutes at 5 C. The supernatant was transferred to a flask and the pelletized pulp was further extracted in pure acetone (1:2 weight per volume) to extract amphiphilic antioxidants within fruit pulp.18 After centrifugation under the above conditions, the extracts were used in the oxygen radical absorbance capacity (ORACFL) assay after suitable dilution with phosphate buffer (75 mmol/L sodium phosphate, pH 7.0). To assess the antioxidant density of fruit juice, six samples of each name-brand and store-brand juice were analyzed in triplicate using the ORACFL assay. All samples were diluted directly without further sample preparation using phosphate buffer (75 mmol/L sodium phosphate, pH 7.0) before antioxidant analysis.
Automated ORACFL Assay The ORACFL assay was carried out using the FLUOstar Optima plate reader equipped with an incubator and two injection pumps according to a previously validated and published method by Prior and colleagues.19 AAPH was used as the peroxyl radical generator and Trolox, a water-soluble analogue of vitamin E, served as the standard. Calibration curves of the standard ranging from 6.25 to 50 mmol/L Trolox were prepared fresh for each assay run. The decrease in fluorescence of fluorescein was determined by measuring excitation at 535 nm and emission at 595 nm to exhibit a fluorescence decay curve based on the antioxidant content of the sample. The final ORACFL values were calculated as the area under the fluorescence decay curve (AUC) according to the following equation: (AUCsampleeAUCbuffer)/ (AUCTroloxeAUCbuffer)dilution factor of sampleinitial Trolox concentration (in millimoles). Antioxidant density results are expressed as millimoles Trolox equivalents (TE)/100 g or millimoles TE/serving.
Statistical Analysis Antioxidant density was reported on a wet weight basis as the meanstandard deviation of all samples analyzed in triplicate. Data for four of the five tested fruits and juices (apple, grape, orange, and grapefruit) were subjected to oneway analysis of variance and Tukey’s honestly significant difference procedure to assess significant differences (P<0.05) in antioxidant density among whole fruit, namebrand 100% juice, and store-brand 100% juice. Because store-brand 100% pineapple juice was not available in any of the retail outlets, data from pineapple fruit and name-brand JOURNAL OF THE ACADEMY OF NUTRITION AND DIETETICS
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RESEARCH pineapple juice were subjected to a Student t test to assess significant differences (P<0.05) in antioxidant density. Statistical analysis was performed using Systat Analytical Software, version 11.0 (2012, Cranes Software International Inc). Percent reductions in antioxidant density were calculated based on the antioxidant density of whole fruit and the mean antioxidant density of both name-brand and store-brand juices combined.
RESULTS AND DISCUSSION Significant differences (P<0.05) in antioxidant density were observed between fruit and fruit juices as well as between name-brand and store-brand 100% juices. Statistical results based on mean ORAC values (mmol TE/100 g) for fresh fruit and fruit juice are depicted in the Figure. The antioxidant density of fresh apple, orange, and grapefruit was 54%, 23%, and 52% higher, respectively, compared with the mean antioxidant density of both 100% juices for each fruit. Despite these antioxidant losses, only fresh apple and grapefruit exhibited a significantly greater (P<0.05) antioxidant content than either name-brand or store-brand juices. These differences may be attributable to steps required in the production of fruit juice, including specific steps aimed at removing certain phenolic compounds, mainly flavonoids, which commonly undergo browning reactions and contribute to haze formation in processed juice.17 As a result of these steps and the removal of fruit pulp and peel before juice processing, many juices exhibit lower antioxidant density than their whole fruit counterparts. The antioxidant density (mmol TE/100 g) of grapes and name-brand grape juice did not differ significantly (P<0.05), yet both were significantly higher (P¼0.004) than storebrand 100% grape juice. Similarly, ORAC values for 100% pineapple juice were 56% higher than for pineapple fruit. These quantitative differences may be the result of the
ascorbic acid that is added to juice blends for both increasing the nutrient content of the juice and providing shelf-life extension by delaying oxidation reactions. Likewise, differences in antioxidant density between name-brand and storebrand juices may be reflective of potential dissimilarities in processing techniques employed or in differing fruit cultivars or varietals used among juice processors. Per-serving differences in antioxidant density (mmol TE/serving) are reported in the Table for all fruits and juices. The calculations were based on the weight in grams of a serving of each fruit as reported in the US Department of Agriculture National Nutrient Database for Standard Reference Release 25.20 A serving of fresh apple and grapefruit provides approximately 50% more antioxidants than a serving of 100% juice from either fruit. On a per-serving basis, 100% grape juice is superior in its antioxidant provision to a serving of fresh grapes. This is likely attributable to the weight differential between a 1-cup serving of fresh grapes (92 g) and a 1-cup serving of 100% grape juice (240 g). Likewise, based on the serving weight differential between a serving of fresh pineapple (165 g) and a serving of pineapple juice (240 g), the antioxidant provision of pineapple juice is superior to a serving of the whole fruit. It should also be emphasized that both name-brand and storebrand juices of each fruit were processed to contain 120% Daily Value of vitamin C in one serving. As such, this may have also contributed to the greater antioxidant density of grape and pineapple juice compared with their fresh fruit forms. Overall, a serving of each fruit contains 90 kcal and between 35% and 61% less sugar than a juice serving, which provides approximately 110 kcal and 17 g sugar. Despite the inconclusive, yet controversial link between intake of sugar-sweetened beverages and the obesity epidemic, research continues to investigate the potential role of greater consumption of sugar-sweetened beverages and
Figure. Antioxidant density (mmol Trolox [Hoffman-LaRoche]/equivalents/100 g) of select whole fruit and 100% fruit juices. Columns sharing letters are not significantly different (P>0.05) based on one-way analysis of variance and Tukey’s honestly significant difference test. 1356
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RESEARCH Table. Per-serving differences in antioxidant density of select whole fruit and 100% fruit juices
Fruit Grape
Sample type
Orange
Grapefruit
Pineapple
Mean TEa (mmol/100 g–SDb)
Weight (g) of 1 c servingc
TE mmol/serving
Fruit
6
213.7327.13
92
194.64
Name-brand juice
3
225.3142.43
240
540.75
Store-brand juice Apple
No. of units tested
3
119.7520.60
240
287.40
12d
403.47144.76
125
504.34
Name-brand juice
3
96.2220.15
240
230.93
Store-brand juice
3
99.8532.47
240
239.65
Fruit
Fruit
6
357.87133.67
165
590.49
Name-brand juice
3
194.3881.99
240
466.52
Store-brand juice
3
186.6982.51
240
448.08
Fruit
6
536.80122.67
230
1234.65
Name-brand juice
3
224.3954.02
240
538.65
Store-brand juice
3
270.994.40
240
650.40
Fruit
6
81.8115.28
165
135.00
125.6383.26
240
301.52
Name-brand juice
6
e
a
TE¼Trolox (Hoffman-LaRoche) equivalents. SD¼standard deviation. c Serving size based on gram weight of 1 cup fresh, raw fruit and serving of 100% juice from Nutrient Database for Standard Reference Release 25.20 d Twelve samples composed of 2 common apple varieties used in juice production (6 samples of each). e Six name-brand juices tested due to lack of availability of store-brand juices. b
increases in body weight.21,22 In addition, although the liquid energy provided by juice is metabolized in the same manner as the energy from solid fruit, the medium (solid or liquid) by which the fruit is consumed has been shown to play a significant role in providing satiety cues.23 Taken collectively, a serving of whole fruit, in most cases, remains the most nutritionally superior form for acquiring beneficial nutrients and phytonutrient-based antioxidants while also providing strong appetitive and compensatory dietary cues. Research such as this assists in moving nutrition science forward by evaluating the antioxidant density of both serving forms of fruit using an assay that measures the total capacity of all antioxidants rather than single antioxidants in fruit. By measuring the overall capacity, the antioxidant density measurements quantitatively represent the synergistic interactions of chain-breaking antioxidants working in concert to quench free radicals and regenerate other antioxidants in food systems and in biological samples.24-26 As a result, these synergistic interactions often provide greater capacity for sustained antioxidant effect than individual antioxidants alone. It is through the use of biologically relevant, total capacity assays that the effect of antioxidants in food systems have been shown to positively influence serum/plasma antioxidant capacity.4,27,28 Nevertheless, it should be pointed out that most compounds with antioxidant functionality, whether vitamin- or phytonutrient-based, perform additional roles in human health beyond their free radicalscavenging ability. The most notable limitation of the study is the inability to determine whether the fruits evaluated were from the same October 2013 Volume 113 Number 10
growing region as fruits used in production of tested juices because environmental conditions during plant growth would be expected to modify the macronutrient, micronutrient, and phytonutrient profile of individual commodities. In addition, a combination of fruit cultivars or varietals may have been used to produce the tested juices, whereas individual whole fruit represents only a single fruit cultivar. In all but two fruits, the antioxidant density of a single fruit cultivar was superior to that of its 100% juice form. To effectively limit these potential confounders, a robust sampling of each fruit and each juice were purchased from two regional grocery chains and one national superstore chain and analyzed in triplicate. It should be stated that the study was conducted to evaluate the antioxidant density of the point-of-sale fruit forms available to consumers. Thus, results of the study reflect an accurate quantitative assessment of the antioxidant density of fruit servings available in consumer markets at any given time point.
CONCLUSIONS Although 100% fruit juice can be part of a nutritious diet, research such as this underscores the DGA, which recommend the majority of fruit intake come from whole fruits due to the inverse relationship between consumption of fruit and vegetables and risk of chronic disease.9 Based on these research findings and recommendations within the DGA, whole fruit remains the preferred form over fruit juice for delivering beneficial antioxidants and fiber while also providing significantly less sugar per serving. JOURNAL OF THE ACADEMY OF NUTRITION AND DIETETICS
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AUTHOR INFORMATION K. M. Crowe is an assistant professor and E. Murray is a master’s student, Department of Human Nutrition, University of Alabama, Tuscaloosa. Address correspondence to: Kristi Michele Crowe, PhD, RD, LD, Department of Human Nutrition, Russell Hall Box 870311, University of Alabama, Tuscaloosa, AL 35487. E-mail: [email protected]
STATEMENT OF POTENTIAL CONFLICT OF INTEREST No potential conflict of interest was reported by the authors.
FUNDING/SUPPORT Funding for research supplies utilized in this research was made possible by the University of Alabama Crenshaw Endowed Research Fund.
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