| This study followed the changes in selected phenolic compounds (i.e., gallic acid, catechin, epicatechin, ellagic acid, and epicatechin gallate) and ellagic acid sediment during storage of muscadine juices and wines using HPLC. Juices and wines from cv. Carlos and Welder (both white) and juices from Noble (red) were produced following standard methods. Most of the samples were heated at 94°C for 5 minutes to accelerate the sediment formation and then stored at room temperature (25°C for a period of up to 52 weeks.; Other studies aimed at explaining the pathway of ellagic acid sediment formation included: (1) A gallic acid juice model study using 0.125 % tartaric acid, 15% sucrose, 12.5% mug/ml and KMn 04, (2) Carlos juice spiked with 50 mug/ml of gallic acid, and (3) Noble and Carlos juices acid hydrolyzed using trifluoroacetic acid (TFAA).; In white cultivars, all phenolic compounds, except catechin, were higher in Carlos juices and wines than in Welder juices, which is probably due to cultivar variation. The sediment was visible in the juices from both white cultivars after approximately 2 weeks, compared to 24 weeks in the wines. In all the samples, there was an increase in gallic acid immediately after heating followed by a decrease. There was also an increase of ellagic acid in solution followed by a decrease, as the ellagic acid started to sediment; the juices had more sediment than the wines. The amount of ellagic acid sediment did not change much over time in the wine, whereas in the juice, the ellagic acid sediment increased over time, leveling off after approximately 24 weeks in Carlos juice. Generally the ellagic acid in solution declined after appearance of ellagic acid sediment, and the ellagic acid sediment increased over time where it reached a maximum of approximately 24 mug/ml in Carlos juice after 24 weeks and 98 mug/ml in Noble hot press juice after 42 weeks. The gallic acid juice model did not result in ellagic acid formation but a compound with approximately the same retention was obtained.; When juice was spiked with 50 mug/ml gallic acid, there was no significant increase (p < 0.05) in ellagic acid in solution or in ellagic acid sediment, which shows that only some of the ellagic acid generates from the dimerization of gallic acid. Juice hydrolysis resulted in a significant increase in ellagic acid. Therefore, most of the ellagic acid could be coming from hydrolysis of higher molecular weight compounds such as ellagitannins. This study has provided information on the behavior of selected phenolic compounds, and their possible use by the muscadine industry to improve the quality of their products. Research on the health benefits of phenolic compounds can use this data, since there is very little data on muscadine phenolic compounds. |
