以茶树单芽和一芽一叶为试验材料,采用恒重法、量筒法、TPA测试和应力应变拉伸测试,研究针形名优绿茶加工过程物料容重、质构特性和拉伸等物理特性的变化规律。结果表明,在针形绿茶加工过程中,茶叶容重呈先增后减的趋势,峰值出现在揉捻叶（含水量56%~58%）,做形后期、固形和干燥过程茶叶容重急剧下降。塑性也呈现先增后降的趋势,在揉捻工序达到最大值,其后在做形过程（含水量58%~23%）均维持在较高水平,而在固形和干燥阶段显著下降。弹性的变化趋势与塑性相反,呈先下降再升高的趋势,在揉捻及做形过程（含水量58%~23%）处于最低水平。加工过程柔软性的变化幅度较小。茶叶的拉伸过程经历线性阶段、非线性阶段和塑性变形到断裂阶段。随着加工的进程,最大力呈先下降后升高（含水率56%~57%）的趋势,拉伸强度则呈增加趋势,弹性模量在揉捻前变化小（含水率56%~57%）,但此后显著增加。相关性分析表明,加工过程茶叶的拉伸强度与含水率呈极显著的负相关。研究结果还表明,单芽和一芽一叶的主要物理特性在加工过程的变化不尽相同。除柔软性接近外,单芽原料的容重、弹性、最大力要高于一芽一叶,但塑性、拉伸强度、弹性模量要小于一芽一叶。除了塑性和柔软性接近外,单芽在各工序的容重和弹性均高于一芽一叶,但一芽一叶的弹性模量和拉伸强度在全过程均高于单芽,最大力在揉捻后显著高于单芽。说明在机械设计原理和加工工艺的掌握方面需要注意原料的差异性。

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.