FACTORS INFLUENCING ELLAGIC ACID PRECIPITATION IN MUSCADINE GRAPE JUICE DURING STORAGE

Ellagic acid sedimentation in white muscadine grape juice was monitored following different processing treatments and storage temperatures. High storage temperatures (40-degrees-C) greatly accelerated sediment formation, and pasteurization (100-degrees-C, 10 min) resulted in a faster sediment formation than sterile filtration. Sediment also increased substantially after juice was hydrolyzed (121-degrees-C and pH 2 for 10 min). Ultrafiltration of juice through a 10,000 or 30,000 dalton membrane resulted in significantly less sediment formation in the juice. Treatment of juice with polyvinylpolypyrrolidone (0.1 - 0.2 g/L juice), egg albumen (6-10 mg/L juice) or gelatin (0.05 - 0.4 g/L juice) resulted in a significant reduction of juice phenolics and sediment formation. A commercial pectinase added to the grapes increased sediment formation and total phenolics in the juice. Levels of ellagic acid in juice were very low and did not correlate well with amount of sediment formed.