Submitted to: Journal of the American Oil Chemists' Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/22/2015
Publication Date: 8/9/2015
Citation: Bakota, E.L., Winkler-Moser, J.K., Berhow, M.A., Palmquist, D.E., Liu, S.X. 2015. Antioxidant activity of hybrid grape pomace extracts derived from Midwestern grapes in bulk oil and oil-in-water emulsions. Journal of the American Oil Chemists' Society. 92:1333-1348.
Interpretive Summary: Liquid cooking oils such as soybean oil are highly susceptible to oxidation as a result of their polyunsaturated fatty acid (PUFA) content. Traditionally, synthetic antioxidants have been used to suppress oxidation in edible oils. However, there is increasing consumer resistance toward the use of synthetic antioxidants, creating new demand for “natural,” or “clean label,” antioxidants to take their place. Agricultural byproducts are ideal for generating new sources of safe antioxidants while simultaneously providing a way to dispose of agricultural waste. Grapes and wines are known to be high in phenolic compounds, as are their waste products. Phenolic compounds have long been investigated as antioxidants for food systems and represent a promising avenue of investigation for use in edible oils. Here we explore eight cold-tolerant grape varieties that are currently grown in Illinois, varieties whose antioxidant activities have not been examined before. We created extracts of byproducts of each variety, and added these extracts to bulk vegetable oil and also to an oil-in-water emulsion system, to assess whether the extracts had any antioxidant activity. It was determined that grape pomace, especially pomace from red grapes, is a good source of phenolic antioxidants.
Technical Abstract: Natural antioxidants to inhibit oxidation in edible oils are in high demand. Grape (Vitis vinifera) pomace is an abundant and inexpensive source of polyphenolic antioxidants, which are responsible for numerous health benefits. We examined pomace from eight varieties of Midwestern hybrid grapes for phenolic content and antioxidant activity. Extracts produced from the pomace of each grape variety were added to bulk soybean oil and oil-in-water emulsions to determine antioxidant activity. While the extracts had relatively little effect in bulk oil, we observed dose-dependent antioxidant effects of some extracts in oil-in-water emulsions. Oxidation in emulsions was assessed by peroxide value, headspace oxygen measurements, gas chromatography of headspace volatiles, and fatty acid analysis. In general, pomace extracts derived from red grapes outperformed those from white grapes, with the Marechal Foch variety showing high antioxidant activity at intermediate concentrations. At higher concentrations, Marechal Foch, Corot Noir, Frontenac, and Norton extracts showed promising antioxidant activity.