Food Product Design: Ingredient Insight - May 2005 - Fruit of the Vine

May 2005

Fruit of the Vine

By R. J. FosterContributing Editor

While one of the best things to happen to fruit was the development of seedless grapes, in reality, chomping down on those grape seeds might not have been a bad idea. Research has proven that grape seeds, in the form of grape seed extract, yield a wealth of healthful benefits.

Bottom-of-the-barrel goodness Leftovers from wine and grape-juice manufacturing provide seeds rich in polyphenolic compounds. These compounds are referred to by many names, most of which are actually synonyms for one another: procyanadins, proanthocyanidins,   procyanidolic oligomers, condensed tannins and pycnogenols.

The problem with identification arises from the immense variety in structure. Base units, called "monomers," come in two basic forms: catechin and epicatechin. These monomers, or single units, can bind together to form dimers, trimers, etc., or they can bind with gallic acid to form catechin or epicatechin gallates, or with esters, glycosides and peptides to form highly complex structures. The term "oligomeric" indicates multiple units, while "proanthocyanidins" refers to the complex flavonoids found in the seeds, yielding the commonly used term, "oligomeric proanthocyanidins" also known as OPCs.

Processors use seeds from red and white grapes to prepare grape seed extracts. Red-grape seeds typically provide higher total polyphenolics than white, approximately 3,500 mg/kg versus 2,800 mg/kg, respectively. The seeds' outer shells contain some proanthocyanidins, which protect the seeds from the oxidative effects of the environment -- ultraviolet light and oxygen. The protection comes at the expense of the proanthocyanidins, though, which is why processors should store seeds destined for extraction under dry and practically anaerobic conditions to preserve the potency of the desirable elements within.

They're grrrrrrrape! Proanthocyanidins hold tremendous interest due to their antioxidant activity. Studies have shown that the antioxidant power of OPCs in grape seeds is approximately twice that of vitamin E, and four times that of vitamin C, as reported in the 1997 article "Oxygen Free Radical Scavenging Abilities of Vitamins C and E, and a Grape Seed Extract Proanthocyanidin Extract In Vitro" (Research Communications in Molecular Pathology and Pharmacology, Vol. 95, No. 2). OPCs might also enhance the absorption of these vitamins by sparing them from oxidation in the body. By scavenging the free radicals associated with so many chronic degenerative conditions, OPCs might reduce the threat of cardiovascular disease, arthritis, hypercholesterolemia and some age-related cancers.

By binding to capillary walls, procyanidin components strengthen blood vessels weakened by aging. Improved venous circulation has also been observed with grape seed extract treatment. In 1998, a study, "Endothelium Dependent Vasorelaxing Activity of Polymeric Phenolics (Flavonoids) Present in Grape Seed Extracts," conducted by the University of California, Davis, showed that grape seed extract helped improve blood-pressure regulation by increasing blood flow -- a benefit to those suffering from high blood pressure, or hypertension.

Researchers also continuously investigate the chemo-protective, cancer-fighting effects of grape seed extract. At the 89th Annual Meeting of the American Association of Cancer Research in 1998, researchers from Creighton University, Omaha, NE; Georgetown University Medical Center, Washington, D.C.; and the University of Nebraska, Omaha described grape seed extract's effects as significant inhibition and intermittent cytotoxicity (cell death) in human cancer cells (breast, lung and stomach), combined with promotion of normal, healthy cell growth.

OPCs have been utilized as anti-inflammatory agents to manage swelling of joints, reduce arthritis pain and mend damaged tissue. For retinal diseases, OPCs might provide options for addressing ocular diseases and disorders, such as cataracts and glaucoma, by inhibiting the activity of damaging enzymes. By preventing the degradation of mast cells that, in turn, release histamines, OPCs also hold promise for those suffering from allergies and other sinus problems.

More than just healthy Product developers can apply the same characteristics of OPCs that protect so many human systems from oxidation to food and beverages to defend important elements of foods. More powerful than tocopherol and ascorbic acid, grape seed extract can inhibit oxidative reactions like those responsible for lipid and vitamin oxidation, as well as the off-flavors and colors that often result. Additionally, grape seed extract displays properties of an emulsifier in oil-and-water systems.

Researchers from the Food Safety Consortium at the University of Arkansas, Fayetteville have shown positive benefits to adding grape seed extract, in conjunction with green-tea extract, to chicken breast prior to irradiation. Although highly effective for elimination of foodborne pathogens, irradiation can cause undesirable changes to product texture and color, as well as create off-flavors and odors. Adding OPCs minimized these objectionable changes without adversely affecting the appearance or water-holding capacity of the chicken. Tests have also shown improvement in juiciness and succulence through shelf life.

Several manufacturers' grape seed extracts have been granted self-affirmed GRAS status. Initially, FDA approved the extracts for use as antioxidants in non-standard-of-identity fruit juices and fruit-flavored beverages at levels up to 210 ppm, and later for cereals, bars and yogurt products. More recently, levels ranging from 0.01% to 0.08% have been specified for use in beverages and beverage bases, breakfast cereals, fats and oils, dairy desserts and mixes, grain products, milk and milk products, processed fruits, and fruit juices.

Increased awareness and approval of grape seed extracts will, no doubt, fuel the growth of new and innovative applications. One such application came late in 2004 when a company in Fullarton, Australia, Wendy's Supa Sundaes, incorporated grape seed extract into a frozen dessert, creating what the company called "the country's first functional ice cream." At 99% fat-free with the same antioxidant level as a serving of grapes, this concept speaks to consumers seeking a treat that also has healthful qualities. If grape seed extract can add a healthful splash of character to a bowl of ice cream, I'll take two scoops, with sprinkles.  

R. J. Foster has over a decade of experience in research & development and technical service in the food industry. A freelance writer specializing in technical communications, he can be reached at [email protected].

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