Optimisation of blueberry vacuum drying process

Drying in a vacuum is one of the drying methods in which moisture is removed from the food at reduced pressure and temperature. The objective of this research was to optimize the vacuum drying of blueberries in order to preserve health benefits phytochemicals using response surface methodology. The drying was performed in a new design of vacuum dryer equipment. Investigated range of temperature was 46-74°C and of pressure 38-464 mbar. Total solids, total phenolics, vitamin C, antioxidant activity, anthocyanin content and total color change were used as quality indicators of dried blueberries. Within the experimental range of studied variables, the optimum conditions of 60 °C and 100 mbar were established for vacuum drying of blueberries. Separate validation experiments were conducted at optimum conditions to verify predictions and adequacy of the second-order polynomial models. Under these optimal conditions, the predicted amount of total phenolics was 3.7 mgCAE/100dw, vitamin C 59.79 mg/100gdw, anthocyanin content 2746.33 mg/100gdw, IC50 0.031 mg/ml, total solids 89.5 and total color change 88.83.