14E-10 |
Changes in anthocyanins, total phenolics and antioxidant capacity during storage of juices made from muscadine grapes grown in South Georgia |
C. C. AKOH1, E. Pastrana-Bonilla1, and G. W. Krewer2. (1) Dept. of Food Science & Technology, Univ. of Georgia, 115 Food Science Bldg., Athens, GA 30602-7610, (2) Dept. of Horticulture, Univ. of Georgia, Rural Development Center, PO Box 1209, Tifton, GA 31793-7548 Muscadine grape is an important food crop indigenous to the Southeastern United States and shares with other grapes a high content of phenolic compounds. The objective of the study was to determine the stability of muscadine grape juices by following changes in total anthocyanins, total phenolics, and antioxidant capacity, during eight weeks storage at two levels of both temperature and ascorbic acid. Fruits from ten cultivars of muscadine grape (five bronze-skin and five purple-skin) were “hot-pressed” to obtain juice. Each juice sample was separated into 4 sub-samples and 0.15% ascorbic acid was added to two of them while no ascorbic acid was added to the other two. Samples were stored at 4°C and 25°C. Each set of samples was prepared in triplicate. Total phenolics were determined colorimetrically using the Folin-Ciocalteu reagent method. Total anthocyanins were determined by a pH-differential method using an UV-visible spectrophotometer. Antioxidant capacity was determined by the TEAC (trolox equivalent antioxidant capacity) assay. Total phenolics and antioxidant capacity values were higher for the samples containing ascorbic acid and showed a decline during the first 4 weeks of storage and then the values stabilized. There was no significant difference between the two temperature groups. Total anthocyanins declined rapidly in the presence of ascorbic acid and when stored at room temperature it degraded almost completely after the 5th week. At refrigeration temperature, the degradation of anthocyanins was less than 20% during the 8 week storage. The results show that phenolic compounds in muscadine juices are not very stable when stored at room temperature. Ascorbic acid imparts some stability to the juices and increases their antioxidant capacity but affects the anthocyanins content.
Session 14E, Nutraceuticals & Functional Foods: General I
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