33F-4 |
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K. P. LAI, Dept. of Agricultural Engineering, Michigan State Univ., 208 G. Malcolm Trout FSHN Bldg., East Lansing, MI 48824-1224, N. J. Matella, Food Science and Human Nutrition, Michigan State University, G.M. Trout Bldg., E. Lansing, MI 48824, and K. D. Dolan, Dept. of Food Science & Human Nutrition/Dept. of Agricultural Engineering, Michigan State Univ., 208 G. Malcolm Trout FSHN Bldg., East Lansing, MI 48824-1224. Anthocyanins are powerful antioxidants that have been shown to degrade under thermally abusive processes. Grape pomace, a by-product of the juice and wine industry and a significant source of anthocyanins, can be dried and further processed as a value-added food additive. In conventional oven drying, heat is transferred by convection to evaporate water from the product; often this requires higher temperatures and/or longer drying times. In catalytic infrared (IR) drying, heat is transferred more efficiently to the water within the product by radiation, requiring lower temperatures and/or shorter drying times. It is hypothesized that the efficiency of heat transfer in catalytic IR drying would help retain more anthocyanins than conventional oven drying. The objective of this investigation was to determine total anthocyanins in grape pomace dried by oven and by catalytic IR drying. Grape pomace (5 g, ~24% moisture content (MC)) was dried to 5-10% MC in an oven drying unit at 77°C for 165 min. and dried similarly in a catalytic IR unit at 4 microns for 60 min. Total anthocyanin levels were determined before and after drying using the pH-differential method. In conventional drying, the product reached an average maximum temperature of 52°C and total anthocyanin content was reduced from 0.103±0.018 AU/g of dry wt. in the raw sample to 0.052±0.010 AU/g of dry wt. in the dried sample, or about a 50% loss of total anthocyanins. Catalytic IR drying showed an average product temperature of 50°C and displayed no significant loss of total anthocyanins (0.103±0.018 AU/g of dry wt. to 0.102±0.011 AU/g of dry wt.). These results indicate that anthocyanins are better retained with catalytic IR drying. This suggests that IR drying may be a cost-effective alternative to high-temperature drying methods for food materials with anthocyanins.
Session 33F, Nutraceuticals & Functional Foods: Antioxidants and phytochemical analysis
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