摘要
为提高蓝莓的真空冷冻干燥速率和品质,对不同隔板温度(40、45、50、55℃)、真空度(65、70、75、80 Pa)及预冻温度(-65、-60、-55、-50 ℃)的干燥效果进行了探讨,研究了不同干燥工艺对蓝莓干燥特性和品质的影响.在单因素试验的基础上,采用响应面法优化确定了蓝莓真空冷冻干燥的最优工艺参数并进行了验证.结果表明:隔板温度、真空度和预冻温度越高,干燥时间越短,干燥速率越快.适当降低隔板温度和预冻温度可以在一定程度上保持冻干蓝莓的颜色、硬度、花青素含量和抗坏血酸含量,并提高复水比,但真空度的降低会增大冻干蓝莓的色差并降低硬度.蓝莓真空冷冻干燥最佳工艺参数为:隔板温度44℃,真空度71 Pa,预冻温度-55℃.研究结果为优化真空冷冻干燥工艺和提升冻干蓝莓的品质提供了理论依据和参考.
Abstract
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.
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