Influence of osmotic concentration, continuous high frequency ultrasound and dehydration on antioxidants, colour and chemical properties of rabbiteye blueberries

Rabbiteye blueberries (Vaccinium ashei Reade) were osmoconcentrated in a sucrose solution for 12 h, and for 3 h, with and without high frequency ultrasound (CHFU). Treated and untreated samples were air-dehydrated (70 degrees C, 10 h). Osmoconcentration decreased titratable acidity and induced a high loss of anthocyanins and phenolics. Approximately 60% of anthocyanins and phenolics were lost during osmoconcentration for 12 h. Air-dehydration further decreased anthocyanins and phenolics, with a higher negative influence on anthocyanins. Dehydration, after osmotic concentration, produced the largest colour differences in comparison to the control. High frequency ultrasound had a negative influence on anthocyanins and phenolics. Antioxidant activity was lowest in osmoconcentrated and dehydrated berries. Combination of high temperature, high sugar concentration and oxygen availability had the largest negative influence on colour and antioxidant properties (anthocyanins and phenolics) of dehydrated rabbiteye blueberries. (c) 2006 Elsevier Ltd. All rights reserved.