Quality evaluation of osmo-convective dried blueberries

The color, texture and rehydration ratios of two-stage osmo-convective dried blueberries were evaluated. The parameters analyzed for color were the total color difference (Delta E) and the red-blue (a/b) ratio. The textural parameters of hardness and stickiness of the osmo-convective dried blueberries were evaluated. The results were compared with those of conventionally air-dried blueberries (worst case scenario) and freeze-dried blueberries (best case scenario). The results showed that osmotic dehydration for a short contact time minimized color losses during convective air-drying. The osmo-convective dried blueberries were not significantly harder (p > 0.05) than the conventional air-dried blueberries. The rehydration ratios of the osmo-convective dried blueberries were lower than the rehydration ratios of freeze-dried and air-dried blueberries. The best osmotic dehydration condition under which the osmo-convective dried blueberries had better color and texture and, a shorter drying time than the conventional air-dried blueberries was 50 degrees C - 55 degrees Brix for 4.5 h.