36E-46 |
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J. LEE and S. T. Talcott. Dept. of Food Science and Human Nutrition, Univ. of Florida, 359 FSHN Bldg., Newell Dr., PO Box 110370, Gainesville, FL 32611-0370 Free ellagic acid increases with hydrolysis of its precursors which include ellagic acid glycosides and ellagitannins and contributes to the development of insoluble sediments in muscadine juice or wine during storage. Prior to investigating chemical or physical methods to remediate these sediments in muscadine grape products, it is important to determine those factors affecting changes in ellagic acid derivatives during storage. The objective of study was to evaluate ellagic acid derivatives in muscadine grape juice and in polyphenolic isolates of the juice in effort to understand their stability and formation of free ellagic acid. Hot-pressed muscadine juice was prepared by blending Noble and Albemarle (1:1) cultivars, which contain high anthocyanins and ellagic acid derivatives, respectively. Juice was filtered and thermally pasteurized (90¢ªC, 5 min) and polyphenolic isolates partitioned from a Sep-Pak C18 cartridge by sequentially washing with water, ethyl acetate, and methanol. The grape juice and resultant isolates were stored at 37¢ªC for 5 weeks and monitored for free ellagic acid, ellagic acid glucoside, ellagic acid xyloside, ellagic acid rhamnoside, and total ellagic acid following acid hydrolysis by HPLC-PDA. Ellagic acid glycosides were evaluated in both ethyl acetate and methanol isolates and was found to be relatively stable during storage with overall decreases ranging from 13 to 35%. Total ellagic acid decreased by 78% during storage in the water-soluble (not retained on C18) isolate, which contained highly polar constituents including ellagitannins, indicating significant degradation of the ellagitannins. Results revealed that changes in free ellagic acid were influenced by ellagitannin degradation rather than ellagic acid glycosides during storage.
Session 36E, Fruit & Vegetable Products: General
2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana |