Cao Lifang, Li Bowen, Zhao Nan, Li Huan, Wang Yanfeng, Yu Xing, Huang Xin
Yellow River Conservancy Technical Institute Kaifeng China.
Bioenergy and Environment Science & Technology Laboratory College of Engineering China Agricultural University Beijing China.
Food Sci Nutr. 2020 Feb 17;8(3):1729-1738. doi: 10.1002/fsn3.1461. eCollection 2020 Mar.
Moisture migration is considered to be one of the most important influencer on crop quality during storage, which is easily affected by storage conditions, such as ambient humidity and temperature. The aim of this work was to determine the effect of storage condition on moisture content of Chinese naked oat by simulating 9 equilibrium relative humidity (ERH) and 5 temperatures. The equilibrium moisture content (EMC) of dry sample was achieved by adsorption, while EMC of wet one was achieved by desorption. EMC of oat increased with the increase in ERH and decreased when temperature increased. The sorption isotherm was a typical "S" shape and fitted using current EMC/ERH models. Modified Chung-Pfost (MCPE) model was the most suitable for describing the dynamic sorption process of Chinese naked oat during storage with a ERH range from 10% to 90%. There was an obvious hysteresis between adsorption and desorption isotherms, whose range decreased with the increase of temperature. High temperature accelerated moisture migration by increasing the hydrophilicity of oat surface. Moreover, dynamic moisture migration was imaged by low-field nuclear magnetic resonance (NMR), showing that moisture migrated between ambient environment and oat mainly through endosperm where most moisture accumulated. During sorption, free water migrated firstly, followed by bound water and the change in content of bound water was more stable than that of free water. The results of this study can provide a useful information for future work on quality control of oat during storage.
水分迁移被认为是储存期间影响作物品质的最重要因素之一，它很容易受到储存条件的影响，如环境湿度和温度。这项工作的目的是通过模拟9种平衡相对湿度（ERH）和5种温度，来确定储存条件对中国裸燕麦水分含量的影响。干燥样品的平衡水分含量（EMC）通过吸附获得，而潮湿样品的EMC则通过解吸获得。燕麦的EMC随ERH的增加而增加，随温度升高而降低。吸附等温线呈典型的“S”形，并使用当前的EMC/ERH模型进行拟合。修正的Chung-Pfost（MCPE）模型最适合描述中国裸燕麦在10%至90% ERH范围内储存期间的动态吸附过程。吸附和解吸等温线之间存在明显的滞后现象，其范围随温度升高而减小。高温通过增加燕麦表面的亲水性加速了水分迁移。此外，利用低场核磁共振（NMR）对动态水分迁移进行成像，结果表明水分在环境与燕麦之间的迁移主要通过胚乳进行，胚乳中积累了大部分水分。在吸附过程中，自由水首先迁移，随后是结合水，结合水含量的变化比自由水更稳定。本研究结果可为未来燕麦储存期间的品质控制工作提供有用信息。
