Optimization of microwave-vacuum drying processing parameters on the physical properties of dried Saskatoon berries

The objective of this study is to optimize the microwave-vacuum drying parameters (microwave power, drying time and fruit load) on the physical properties of dried Saskatoon berries. Response surface methodology combined with central composite rotatable design was used to observe the effect of microwave-vacuum drying processing variables and optimize the drying conditions for the physical properties as response variables (moisture content, rehydration ratio, hardness, L value and total color difference) of the microwave-vacuum dried Saskatoon berries. The response variables were effectively modeled as the function of independent variables for the regression as well as response surface modeling. The regression and response surface modeling indicated that increasing microwave power and drying time and deceasing fruit load decreased moisture content but increased rehydration ratio, hardness, L value and total color difference of the microwave-vacuum dried Saskatoon berries. Also, the numerical combining with graphical optimization indicated that microwave power (5.8 – 6.5 kW), drying time (52-59 min) and fruit load (10-10.25 Kg) were very effective to improve the studied physical properties of the dried Saskatoon berries. The findings are expected to be helpful for the process development of commercial scale microwave-vacuum drying of Saskatoon berries within the experimental range.