基于低场核磁的紫薯片真空冷冻干燥过程中水分变化  

Water Changes of Purple Sweet Potato Slices Using Low-field NMR during Vacuum Freeze Drying

作　　者：孙江丽 李瑞 朱洪梅 SUN Jiangli;LI Rui;ZHU Hongmei(College of Food Science,Shanxi Normal University,Linfen 041004,China)

机构地区：[1]山西师范大学食品科学学院,山西临汾041004

出　　处：《食品工业科技》2021年第7期9-14,共6页Science and Technology of Food Industry

基　　金：国家自然科学基金(31401435);山西师范大学自然科学基金(2018-03)。

摘　　要：为探究紫薯片在真空冷冻干燥过程中的水分变化规律和干燥效果,通过低场核磁共振与成像对紫薯片内部水分存在形式及其含水量变化进行研究;通过体视显微镜和色差计观察紫薯片的微观结构与色泽变化。结果表明:在干燥过程中,紫薯片除去的主要是自由水、部分结合水和半结合水,半结合水量呈先增大后减小的趋势,整个反演图谱向T22峰转移;随着干燥的进行,紫薯片含水量持续下降,伪彩图的亮度和清晰度随之降低。在干燥效果方面,显微结构观察发现水分升华,其先向紫薯片两侧进行扩散,水分脱除后,紫薯片形成疏松多孔结构;干燥时间延长可以提高紫薯片的亮度,但对其色泽影响很小,可用于开发紫薯产品。In order to explore the dynamic law of water and the drying quality of purple sweet potato slices during the vacuum freeze drying,the existential form of internal water and the change of water content in purple sweet potato slices were studied by low-field nuclear magnetic resonance and imaging techniques.Additionally,during the drying,stereoscopic microscope and color difference meter were used to observe the microstructure and the color change of purple sweet potato slices respectively.As a result,purple sweet potato slices removed most of free water and partial bound water and semibound water,the volume of semi-bound water tended to increase and then decrease,and the whole of inversion spectrum of transverse relaxation shifted to T22 peak.With the drying process,the water content in purple sweet potato slices continued to decline,and the brightness and the clarity of the pseudo-color images accordingly decreased.In terms of drying effect,the observation of microscopic structure showed that the sublimation of water first diffused to both sides of purple sweet potato slices where the purple sweet potato slices formedloose porous structure after water removed.Prolonging the drying time can improve the brightness of purple sweet potato slices,but had little effect on the color.Hence vacuum freeze drying can be used to develop purple sweet potato slices as leisure food.

关 键 词：紫薯片 真空冷冻干燥 低场核磁共振 水分 

分 类 号：TS255.36[轻工技术与工程—农产品加工及贮藏工程]