渗透预处理对冷冻干燥苹果片物理品质的影响

Effect of Osmotic Pretreatment on Physical Property of Freeze-dried Apple Slices

为了寻找较优的糖渗透预处理工艺,以改善冷冻干燥苹果脆片的质构特性和吸湿性,本试验以硬度、脆度、色泽、水分吸附性质和微观结构为主要指标,研究了5种不同的40%糖渗透液(果糖、葡萄糖、蔗糖、麦芽糖、低聚异麦芽糖)和不同渗透时间(0、30、60、90、120、180、240 min)对真空冷冻干燥苹果片物理品质的影响。结果表明,冻干苹果片的硬度随渗透时间的延长而增加,采用果糖渗透120 min时,产品硬度较大且脆度损失小,色泽和微观结构保持较好;相同水分活度时平衡含水率随渗透时间的增加而降低;苹果脆片水分吸附模型显示,Gunary模型具有最小的均方根误差和最高的R2,对水分吸附等温线可以进行有效预测。

The aim of this study was to find the optimum osmotic pretreatment method to improve the texture and water adsorption properties of freeze-dried apple slices.This study investigated the effect of different osmotic solution(fructose,glucose,sucrose,maltose,isomaltooligosaccharide)with 40%concentration and different dehydration time(0,30,60,90,120,180,240 min)on the physical properties of apple slices.The results showed that the hardness of freeze-dried apple slices increased with increasing osmotic dehydration time.The freeze-dried apple slices osmotic dehydrated 120 min with fructose showed the highest hardness and minimum crispness loss.The equilibrium moisture content of dried apple slices decreased with increasing water activity.Analysis of the moisture adsorption model of apple slices showed that the Gunary model was suitable to describe the isothermal moisture sorption of freeze-dried apple slices osmotic dehydrated by different sugars,because of the lowest root-mean-square error and the highest R^(2).