Optimization of Vacuum Freeze-Drying Process for Blueberries
In this study,the drying effects of different shelf temperatures(40,45,50,55 ℃),vacuum degrees(65,70,75,80 Pa)and pre-freezing temperatures(-65,-60,-55,-50 ℃)on blueberries were studied,in order to improve the vacuum freeze-drying rate and qualities.On the basis of single factor experiments,response surface methodology was applied to optimize and determine the optimal process parameters for vacuum freeze-drying of blueberries,and the results were verified.The results showed that the higher the shelf temperatures,vacuum de-grees,and pre-freezing temperatures,the shorter the drying time and the faster the drying rates.The decrease in partition temperatures and pre-freezing temperatures could maintain the color,hardness,anthocyanins and ascorbic acid contents of freeze-dried blueberries to a certain extent,and improve the rehydration ratios.However,the de-crease in vacuum degrees would increase the color difference of freeze-dried blueberries and reduce the hardness.The optimal process parameters for vacuum freeze-drying blueberries were determined as follows:shelf temperature of 44 ℃,vacuum degree of 71 Pa,and pre-freezing temperature of-55 ℃.The research results can provide theo-retical basis and references for optimizing the vacuum freeze-drying process and improving the qualities of freeze-dried blueberries.
万方数据
维普
