中国农业科学 ›› 2022, Vol. 55 ›› Issue (2): 390-402.doi: 10.3864/j.issn.0578-1752.2022.02.013

• 食品科学与工程 • 上一篇    下一篇

3种粳稻籽粒水分解吸过程中的裂纹变化

邵小龙(),徐文,王潇,杨晓静,沈飞,刘琴   

  1. 南京财经大学食品科学与工程学院/江苏省现代粮食流通与安全协同创新中心,南京 210023
  • 收稿日期:2021-05-28 接受日期:2021-08-10 出版日期:2022-01-16 发布日期:2022-01-26
  • 作者简介:邵小龙,Tel:13951895750;E-mail: sxlion2@gmail.com
  • 基金资助:
    科技部重点研发项目(2017YFC1600601);江苏高校优势学科建设工程资助项目(PAPD)

Fissure Development of Three Japonica Rice Grain during Water Desorption

SHAO XiaoLong(),XU Wen,WANG Xiao,YANG XiaoJing,SHEN Fei,LIU Qin   

  1. College of Food Science and Engineering, Nanjing University of Finance and Economics/The Jiangsu Province Center of Cooperative Innovation for Modern Grain Circulation and Security, Nanjing 210023
  • Received:2021-05-28 Accepted:2021-08-10 Online:2022-01-16 Published:2022-01-26

摘要:

【目的】基于食品水分吸附解吸理论,检测粳稻裂纹与水分含量,探讨籽粒裂纹的发展变化原因,总结粳稻裂纹的发展规律。【方法】以‘软玉’‘淮稻5号’和‘南粳5055’3种粳稻作为研究对象,利用X射线成像技术检测粳稻籽粒的裂纹粒及裂纹程度;采用扫描电镜观察‘南粳5055’籽粒裂纹断裂面的微观结构;使用LF-NMR技术检测粳稻籽粒的水分在解吸过程中的特征变化,分析粳稻籽粒水分解吸过程中裂纹数据和水分分布的相关关系。【结果】利用LF-NMR技术可以准确地预测不同品种粳稻籽粒的水分含量。裂纹率随籽粒的水分解吸程度而上升,‘软玉’‘淮稻5号’和‘南粳5055’籽粒裂纹率分别在水分含量低于14.96%、15.21%和17.84%后明显增加。低水分籽粒内裂纹数量高于高水分籽粒。粳稻裂纹粒与非裂纹粒内部断裂面的淀粉和细胞结构差异明显。水分解吸导致淀粉粒间断裂面发展为细胞间断裂面,即初期裂纹。当裂纹数量继续增加,初期裂纹发展成为可被观察到的裂纹,裂纹类型从轻度发展到中度或重度。水分解吸导致籽粒横向弛豫时间T21T22缩短;结合水含量减少,“自由水”含量先减少后增多,各状态水分间存在迁移和转化现象。部分“自由水”在水分解吸过程中挥发离开籽粒,同时部分“结合水”转化为“自由水”。总体表现为“结合水”面积和相对面积比例随水分解吸过程逐渐减小,而“自由水”的面积有增有减,但相对面积比例呈上升趋势。因此,在稻谷水分解吸过程中,除了含水量下降,各组分水分流动性下降,“结合水”含量降低也是水分变化的重要特征。裂纹与水分数据相关分析表明,裂纹变化与各组分水的横向弛豫时间和“结合水”含量的变化相关,与“自由水”含量不相关。【结论】本研究提出了一种将稻谷籽粒按照裂纹数量和种类分成4类裂纹粒的方法。粳稻水分解吸过程中裂纹类型变化与水分分布密切相关,籽粒水分的迁移和转化,特别是“结合水”下降,是籽粒裂纹变化的重要原因。

关键词: 粳稻, 水分解吸, 裂纹, X射线成像, 低场核磁共振, 扫描电镜

Abstract:

【Objective】 Based on the explanation of food moisture adsorption/desorption, were used to detect fissures and moisture in japonica rice. The aim of this study was to investigate the change of grain kernel fissures and to summarize the development law for the fissures in grain kernels. 【Method】Three japonica rice, Ruanyu, Huaidao 5 and Nanjing 5055 were investigated. The japonica rice kernels with fissures and the degree of fissures were detected by X-ray imaging technology. The microstructure of fissures in Nanjing 5055 was observed by scanning electron microscope. Water characteristics in three japonica rice grains were measured by LF-NMR technology. The relationship between kernel fissure and water characteristics was analyzed. 【Result】 A model based on the low-field nuclear magnetic data accurately predicted the moisture content of three japonica rice. The number of fissures increased with increasing the degree of water desorption of the grains. The percentage of fissure kernel for the rice varieties Ruanyu, Huaidao 5, and Nanjing 5055 increased significantly when the moisture content was lower than 14.96%, 15.21%, and 17.84%, respectively. The percentage of fissure kernel decreased with moisture content in paddy rice kernels. The microstructure of starch and cell on the internal fracture surface of cracked kernels were very different from that of the control sample. The water desorption led to the production of starch granules and cell fracture surfaces, and this fracture surface was the initial fissure. When the number of fissures continued to increase, the initial fissures developed into observable fissures. These fissures were developed from slight level to moderate and even severe level. The water desorption led to the shortening of the transverse relaxation time T21 and T22 of the grain kernel. The content of “bounded water” decreased, whereas the content of “free water” initially decreased and then increased. There was a migration and transformation of water molecules between the bounded and free water. Therefore, in addition to the decrease of moisture content, the molecular mobility of each water component decreased, and the decrease of “bound water” content was also an important feature of water change in the process of water desorption of paddy rice. Correlation analysis between fissures and moisture showed that fissures changes were related to changes in the transverse relaxation time of each water component and “bound water” content, but not related to the “free water” content. 【Conclusion】This study proposed a method to classify grain kernel into four types based on the number and types of cracks. The change of crack type in the process of water decomposition was closely related to water distribution. The migration and transformation of grain moisture, especially the decrease of bound water, were the important factors affecting the changes of grain fissures.

Key words: Japonica rice, moisture desorption, fissure, X-ray imaging, nuclear magnetic resonance, scanning electron microscope