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Journal of Tea Science ›› 2019, Vol. 39 ›› Issue (6): 705-714.

### Research on Main Physical Properties of Tea Leaves in High-quality Green Tea Processing

LI Chen1,2, AI Zeyi1, YU Zhi1, CHEN Yuqiong1, NI Dejiang1,*

1. 1. College of Horticulture and Forestry Sciences Huazhong Agricultural University/Key Laboratory of Horticultural Plant Biology, Ministry of Education, Wuhan 430070, China;
2. Jiangxi Sericulture And Tea Research Institute, Nanchang 330203, China
• Received:2019-01-24 Revised:2019-02-27 Online:2019-12-15 Published:2019-12-24

Abstract: Taking one bud and one bud with one leaf of tea as the test materials, the variations of physical properties of tea leaves such as bulk density, texture and tensile properties in needle-shaped green tea processing were studied by the method of constant weight and graduated cylinder, TPA and stress-strain tensile test. As a result, the bulk density of tea leaves was first increased and then decreased, with the peak in the rolled leaves (water content 56%-58%). it was sharply decreased during the post-forming, fixing and drying processes. The plasticity presented the same trend with the maximum appeared in the rolling process. It then remained a high level in the forming process (water content 58%-23%), and declined significantly during the fixing and drying processes. The trend of elasticity was opposite to the plasticity, with the lowest level in the rolling and forming processes (water content 58%-23%). Less variation was observed in flexibility during the whole processing. The tensile process of tea leaves undergoed linear, nonlinear and plastic deformation to fracture stages. The trend of maximum force was decreased first and then increased (water content 56%-57%). The tensile strength was increased during the whole processing. The elastic modulus varied a little before the rolling process and then increased significantly. The correlation analysis shows that the tensile strength of tea leaves was significantly and negatively correlated with water content in the processing, and the diversification of main physical properties of one bud and one bud with one leaf in processing were not exactly the same. Besides the similar level of plasticity and flexibility, the bulk density, elasticity and maximum force of one bud were higher than that of one bud with one leaf. While the plasticity, tensile strength and elastic modulus showed an opposite trend. In the whole processing, apart from the similar level of plasticity and flexibility, the bulk density and elasticity of one bud in each process were higher than that of one bud with one leaf, but the elastic modulus and tensile strength showed an opposite trend. the maximum force of one bud with one leaf was significantly higher than that of one bud after the rolling process. In conclusion, the differences in raw materials should be emphasized in the principles of mechanical design and processing techniques.

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