超声渗糖工艺对猕猴桃冻干时间的影响及响应面优化

Effect of Ultrasonic-assisted Sugar Osmotic Pretreatment on Dehydration Time and Optimization of Freeze-drying Kiwifruits

[目的]优化猕猴桃渗糖工艺,缩短猕猴桃冷冻干燥时间,提高冻干猕猴桃的品质。[方法]采用单因素试验,确定理想的糖液质量分数及超声作用时间、温度和功率范围,并通过响应面法优化冻干猕猴桃的超声渗糖工艺。[结果]单因素试验表明,猕猴桃的干燥时间随着超声作用温度的增加而延长,40℃以上的温度会使干燥时间陡增;相反地,随着超声功率和糖液质量分数的增加,猕猴桃干燥时间整体上呈现缩短的趋势;此外,猕猴桃干燥时间随着超声作用时间的延长而缩短,并逐渐趋于稳定。响应面优化并修正后的超声渗糖最佳工艺条件:糖液质量分数45%,超声作用时间、功率和温度分别为50 min、200 W和24℃。该条件下猕猴桃干的干燥时间为43.07 h,硬度14616.01 g,咀嚼性7795.61 mJ,维生素C和总糖含量分别为0.19%和62.82%,并且感官品质得到进一步提升。[结论]优化后的超声渗糖工艺较传统糖渍工艺(不使用超声辅助)可显著缩短猕猴桃冻干时间,并且最终的产品质量更佳,口感更为酥脆。

Objective The process to freeze-dry kiwifruits was optimized using an ultrasonic-assisted sugar osmotic pretreatment to shorten the drying time and improve the product quality.Method Single factor tests were conducted to determine the ranges of sugar concentration as well as ultrasonic application time,temperature,and power for the pretreatment prior to process optimization by a Box-Behnken response surface experiment.Result The time required to freeze-dry kiwifruits increased significantly when the treatment temperature was raised,especially,beyond 40℃.On the other hand,the time was shortened as the ultrasonic power and sugar concentration increased.Prolonged ultrasonic application also reduced the drying time to a leveled off minimum.The optimized pretreatment applied 200W ultrasound at 24℃for 50m on fresh kiwifruits impinged with 45%(w/w)sugar.The freeze dehydration took 43.07h to yield kiwifruit pieces with a hardness measurement of 14,616.01g,a chewiness of 7,795.61mJ,a vitamin C content of 0.19%,and a total sugars content of 62.82%.The sensory evaluation rated the test product much superior to control without pretreatment.Conclusion The freeze-drying process optimized with ultrasonic-assisted sugar osmotic pretreatment on kiwifruits required significantly shortened dehydration time and produced products with superior quality in comparison with the conventional technology.