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Journal of Tea Science ›› 2020, Vol. 40 ›› Issue (2): 194-204.doi: 10.13305/j.cnki.jts.2020.02.006

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Study on the Changes of Physical and Chemical Components during the Frying Process of Green Tea by Computer Vision

WU Xun1,2, LIU Fei3, CHEN Zhiwei2,4, WANG Yuwan2, CHEN Lin2, TU Zheng2, ZHOU Xiaofen5, YANG Yunfei2, YE Yang2*, TONG Huarong1*   

  1. 1. College of Food Science, Southwest University, Chongqing 400715, China;
    2. Tea Research Institute, Chinese Academy of Agricultural Sciences, Hangzhou 310008, China;
    3. Tea Research Institute of Sichuan Academy of Agricultural Science, Chengdu 610066, China;
    4. Faculty of Mechanical Engineering & Automation, Zhejiang Sci-Tech University, Hangzhou 310018, China;
    5. Agricultural and rural Bureau, Wuyi 321200, China
  • Received:2019-11-12 Revised:2019-12-30 Online:2020-04-15 Published:2020-04-20

Abstract: In order to find out the physical and chemical changes during the frying process of green tea, the computer vision technology was applied to real-time monitor the changes of color and shape, and chemical changes were simultaneously measured. The results show that with the increase of frying time, (1) the radius of curvature of unfinished tea gradually decreased, which showed the highest decreasing rate from 10-30 min. R, G, B and average gray value decreased first and then rose. The consistency value was opposite to their trends, with the extreme value in 20 min. H value increased significantly, S value decreased significantly. (2) Epigallocatechin gallate (EGCG), epigallocatechin (EGC), chlorophyll a, chlorophyll b and carotenoids decreased significantly, while gallocatechin gallate (GCG) increased significantly. Experimental results show that the radius of curvature was highly correlated with water content and leaf temperature. H was significantly correlated with chlorophyll a, chlorophyll b. S was significantly correlated with chlorophyll a, carotenoids and epicatechin gallate (ECG). The linear fit of EGCG and H values showed the highest value at 0.922 1. In the future, water content, leaf temperature and H value could be monitored online to predict changes of the radius of curvature and chemical composition during frying.

Key words: computer vision, green tea, the frying process, the radius of curvature, correlation

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