Optimizationof Vacuum Freeze-Drying Conditions of Kiwifruit Powder

The influence of the vacuum freeze drying conditions of kiwifruit pulp,including the pressure,thickness of frozen pulp and heating temperature,on the properties of dried kiwifruit powder,such as the vitamin-C content,drying-rate and color difference,was analytically investigated in Box-Behnken response surface design,mathematically formulated with quadratic regression model,numerically simulated in genetic algorithm and experimentally evaluated for the process optimization.Freeze-dried under the optimized conditions,including a thickness of 8 mm,a pressure of 20 Pa and a temperature of 40℃,the kiwifruit powder had a vitamin-C content of 51.75 mg/10 g,a color difference of 3.82 and a drying-rate of 1.89%/h.We suggest that the self-developed quadratic regression model be of some theoretical and technological interest in production of vacuum freeze-dried kiwifruit power on industrial scale.