不同干燥方式对苹果片质构的影响及其与果胶性质的关系

Influence of Different Dehydration Processes on the Texture and Pectin Characteristics of Apple Chips

为明确不同干燥方式对苹果片微观结构及果胶的影响,探讨干燥苹果片质构与果胶性质的关系,采用热风干燥(hot air drying,AD)、压差闪蒸干燥(instant controlled pressure drop drying,DIC)、真空冷冻干燥(freeze drying,FD)等技术处理原料,分析脱水苹果片硬脆度和微观结构,以及果胶含量、酯化度和中性糖等性质的变化。结果表明:DIC苹果片脆度最大,并有较好的均匀蜂窝状结构;与未处理鲜样相比,干燥处理后的苹果片水溶性果胶(water-solute pectin,WSP)含量和分子的线性度下降,螯合性果胶(CDTA-solute pectin,CSP)含量和分子的线性度上升,且WSP含量和线性度随着热风干燥温度的上升而下降,CSP具有相反的趋势;AD 90℃和DIC获得的脱水苹果片的CSP酯化度最小,分别为24.9±1.2%和23.3±0.4%。综合分析,WSP含量影响脱水苹果片硬度和干燥过程中多孔结构的形成,而酯化度则是影响脱水苹果片脆度的重要因素之一。

The effects of different drying methods on the microstructure of apple chips and pectin content and characteristics were investigated to explore the relationship between the texture of dried apple chips and pectin properties. Hot-air drying（AD）, instant controlled pressure drop（DIC）, and vacuum freeze-drying（FD） were used to process the raw materials. The degree of crispness and microstructure of dehydrated apple chips, and the changes in the pectin content, degree of methoxylation, and neutral sugars were investigated, and the relationship between pectin modification and texture properties of the products was analyzed. The results showed that DIC-dried apple chips exhibited the highest crispness and a honeycomb structure with uniform pores. Compared with fresh apple slices, the dehydrated apple chips showed a decrease in the water soluble pectin（WSP） content and linearity of WSP molecules, and an increase in the cyclohexane diamine tetraacetic acid（CDTA）-soluble pectin（CSP） content and linearity of CSP molecules. In addition, with increasing hot-air drying temperature, the WSP content and linearity decreased, and the CSP content and linearity increased. The degrees of methoxylation（DM） of the CSP for AD 90 ℃and DIC apple chips were higher than those of the other samples at 24.9±1.2% and 23.3±0.4%, respectively. In summary, the content of WSP affected the hardness of dehydrated apple chips and the formation of a porous structure during the drying process, while DM was an important factor affecting the crispiness of dehydrated apple chips.