EFFECTS OF PRE-TREATMENTS ON DRYING KINETICS ANDANTHOCYANIN CONTENT IN DRIED BLUEBERRIES

摘要

Osmotic dehydration and skin abrasion were used as pre-treatments to reduce dryingtime and preserve total anthocyanin content of Vaccinium corymbosum L. (highbush)and Vaccinium ashei (rabbiteye) blueberries. Multi-stage drying at 90 °C for 90 minutes,70 °C for 120 minutes and 50 °C until the water activity reached 0.60-0.65 and lowtemperature drying at 40 °C and 10% relative humidity were used. Skin abrasionprovided more significant reduction in drying time than the osmotic dehydration. Byusing skin abrasion, drying time of the multi-stage dried samples was decreased from24.5-27.5 hours to 6.5 hours. Similarly, the drying time was reduced from 9-10 days to2-3 days for low temperature dried samples. The results obtained by LC/MS showed thatpre-treatments and drying methods affected each anthocyanin in a different way. Thedried samples with the highest total anthocyanin content (10.6 ± 0.7 and 3.9 ± 0.3 mgcyanidin 3-glucoside equivalents/g dry weight for highbush and rabbiteye blueberries,respectively) were the samples treated by skin abrasion prior to multi-stage drying.