Fruits Pack a Punch

Packed with antioxidants, fiber, and phytochemicals, fruits are one of nature’s nutraceutical gifts to the food industry. Halvorsen et al. (2006) studied the antioxidant concentration of more than 1,000 foods and beverages and showed that blackberries, grape juice from Concord grapes, and strawberries contained the highest levels of antioxidants. Food formulators can take advantage of a bounty of fruits in forms such as juices, concentrates, extracts, and dehydrated, capitalizing on each individual fruit’s benefits. Here is a look at some fruits that pack a nutritional punch.

• Açai. A palm berry, açai is growing in popularity thanks to its nutritional benefits, primarily its high antioxidant content. Schauss et al. (2006a) showed that anthocyanins, proanthocyanidins, and other flavonoids were the major phytochemicals found in standardized freeze-dried açai fruit pulp/skin powder. In a separate study, Schauss et al. (2006b) showed that antioxidants in freeze-dried açai are able to enter human cells in a fully functional form and to perform an oxygen-quenching function at very low doses.

• Apples. He and Liu (2007) recently identified 13 compounds called triterpenoids in apple peel that either inhibited or killed cancer cells in laboratory cultures. Most of the triterpenoids showed a high potential of anticancer activities against three human cancer cell lines: HepG2 liver cancer cells, MCF-7 breast cancer cells, and Caco-2 colon cancer cells. The results indicated that triterpenoids isolated from apple peels have potent antiproliferative activity and may be partially responsible for the anticancer activities of whole apples.

Last year, New Zealand–based HortResearch (phone +64-9815-4200, www.hortresearch.co.nz) released an extensive collection of more than 50,000 apple gene sequences called expressed sequence tags (ESTs) (HortResearch, 2006). The apple ESTs hold the secrets to discovering how gene function controls all aspects of fruit development, including taste, color, vitamin content, and how fruit fight plant diseases. The company says its apple EST database is already being employed to support the company’s own breeding programs for novel apple varieties, including a red-fleshed apple.

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• Blueberries. According to information from the U.S. Highbush Blueberry Council, Folsom, Calif. (phone 916-983-0111, www.blueberry.org), blueberries contain 14 mg of vitamin C and 0.8 mg of vitamin E/cup as well as anthocyanins and phenolics that act as antioxidants. Blueberries are used as an ingredient in cereals and baked goods, but Leheska et al. (2006) showed that there is an expanding potential for blueberries. The researchers added blueberry puree at 5% and 10% to precooked pork breakfast sausage patties and found that the phenolic content in the cooked sausage increased by an average of 36%. When children 10–12 years old evaluated the sausage patties that contained the puree and compared them to a control, they liked the patties with 5% blueberry puree as much as the control patties and did not report a difference in taste, mouthfeel, or appearance.

Pons (2007) reported that U.S. Dept. of Agriculture Agricultural Research Service scientists showed that blueberries can reduce cholesterol and cancer. ARS chemist Agnes Rimando and collaborators found that hamsters fed a diet extremely high in cholesterol but supplemented with freeze-dried skins of rabbiteye blueberries produced plasma total cholesterol levels 37% lower than hamsters fed a control diet. The hamsters that were fed the blueberries had LDL cholesterol levels 19% lower than hamsters fed a control diet. According to Rimando, the results may be linked to constituents, including resveratrol and pterostilbene in blueberry skins that can activate a protein involved in the breakdown and import of fats. Rimando collaborated in another study that demonstrated pterostilbene’s potential to fight colon cancer. Nine rats fed a diet supplemented with 40 ppm of ptero-stilbene showed 57% fewer induced colon lesions than nine other rats fed an unsupplemented diet.

• Cherries. Tart cherries, which are high in antioxidants, contain other important nutrients such as beta carotene, vitamins C and E, potassium, magnesium, iron, fiber, and folate. In addition, cherries are one of the few food sources of melatonin, a potent antioxidant that helps improve the body’s circadian rhythms and natural sleep patterns, according to information from the Cherry Marketing Institute, Danville, Calif. (phone 925-838-5454, www.choosecherries.com).

Recently, University of Michigan researchers showed that cherries may help lower the risk of metabolic syndrome and cardiovascular disease (CMI, 2007). The researchers gave two groups of rats tart cherry powder at 1% or 10% of their diet for 90 days. The results showed that the cherry-enriched diets significantly lowered total cholesterol levels, triglycerides, insulin, and fasting glucose levels. The rats fed the cherry-enriched diets also had lower levels of a plasma marker of oxidative damage, increased blood antioxidant capacity, and reduced accumulation of triglycerides and cholesterol in the liver.

• Cranberries. Recent research shows that cranberries and cranberry products contain significant amounts of antioxidants and other phytonutrients that may help protect against heart disease, cancer, and other diseases. "Consumers are certainly aware that the cranberry is good for them in preventing urinary tract infections, which happens to be the second leading cause of lost work time for women," says Martin Starr, Science Advisor, Cranberry Institute, East Wareham, Mass. (phone 800-295-4132, www.cranberryinstitute.org). "Health professionals as well as food scientists are aware of this benefit, and in addition, know that cranberries are one of the leading fruits and berries in terms of total antioxidants."

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Cranberries are unique in the fact that they have a characteristic called bacterial anti-adhesion, explains Starr. "The cranberry gets in the way of certain pathogenic bacteria from adhering to cell surfaces. Proanthocyanidins (PACs) are the compounds responsible for this anti-adhesion. Many fruits and vegetables have PACs of the same class; however, the ones associated with cranberries have a unique structure, A-linkages. Most other foods have beta linkages." Cranberry PACs prevent certain bacteria from adhering to the urinary tract wall, including Escherichia coli, associated with urinary tract infections. The anti-adhesion properties of cranberry may also inhibit the bacteria associated with gum disease and stomach ulcers.

Starr adds that cranberry research is still emerging. "New work includes one researcher looking at cranberry’s effectiveness in reducing the likelihood of flu infection. There is also preliminary work on cranberry’s bactericidal effect, which could be interesting in terms of food safety issues."

• Grape Seed Extract. Kaur et al. (2006) studied grape seed extract’s (GSE) in-vitro and in-vivo anticancer effects and associated mechanisms on human colorectal cancer HT29 and LoVo cells in culture. The in-vivo effect of GSE was examined on HT29 tumor xenograft growth in athymic nude mice. The researchers fed the mice a 200 mg/kg dose of GSE. They found that the GSE showed a time-dependent inhibition of tumor growth without any toxicity and accounted for a 44% decrease in tumor volume per mouse after 8 weeks of treatment. GSE inhibited cell proliferation but increased apoptotic cell death in tumors. The researchers concluded that GSE may be an effective chemopreventive agent against colorectal cancer.

• Mangosteen. This fruit is said to help maintain intestinal health, strengthen the immune system, and neutralize free radicals. Xanthones are one of the major phytonutrients found in the rind of mangosteen. Walker (2007) recently developed an analytical method for testing and measuring xanthones in mangosteen rind. The peer-reviewed, single-lab-validated high-performance liquid chromatography analysis of selected xanthones in mangosteen fruit study utilized AOAC protocols.

• Noni. This greenish white tropical fruit about the size of a potato is high in antioxidants. It is used in a variety of products from skin care products to juice and dietary supplements. The reported benefits include increased energy levels and healthy immune systems. West et al. (2006) reported that a safety review of noni juice showed that it is as safe as other fruit juices. Several preclinical safety tests and a human clinical safety study have revealed no adverse health effects, even when the fruit is consumed at high doses.

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• Pomegranate. The antioxidant content and heart-health benefits of pomegranate polyphenols have been demonstrated in numerous in-vitro and in-vivo experiments. Lei et al. (2007) investigated the anti-obesity effects of pomegranate leaf extract (PLE) in mice fed a high-fat diet designed to induce obesity and hyperlipidemia. The mice that consumed PLE showed a significant decrease in body weight, energy intake, and various adipose pad weight percents after a 5 week-treatment period. PLE showed a significant difference in decreasing the appetite of obese mice fed a high-fat diet, but showed no effect in mice fed a normal diet. The researchers concluded that PLE can inhibit the development of obesity and hyperlipidemia in high-fat-diet-induced obese mice.

• Watermelon. This fruit is a good source of citrulline, which is metabolized to arginine, an amino acid needed for heart and immune health. Collins et al. (2007) studied whether watermelon juice increases the amount of arginine, ornithine, and citrulline in humans. The researchers gave 12–23 subjects either no watermelon juice (control), 1 g of watermelon juice/day (low), or 2 g of watermelon juice/day (high) for 3 weeks. The fasting plasma arginine concentrations in subjects increased 11% in the subjects who consumed the low amount of watermelon and the arginine and ornithine concentrations increased 18% and 16%, respectively, in the subjects who consumed the high watermelon amount compared to the control group. Citrulline concentrations did not increase relative to the control but remained stable throughout the study. These results indicated that watermelon provides natural citrulline and arginine to humans, which may be useful in human health studies.

by Linda Milo Ohr,
Contributing Editor,
Denver, Colo.
[email protected]

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