Study on the Variation Law of the Main Mechanical Properties in the Processing of Longjing Tea

Abstract

Fresh tea leaves, both single bud and one leaf with a bud, were used as the test materials in this study. The variation in the main mechanical properties, such as texture and tensile properties, during the processing of Longjing tea was examined by using texture profile analysis (TPA) and stress–strain tensile tests. The plasticity showed a trend of first increasing and then decreasing during the processing, whereas the elasticity displayed the opposite tendency. The flexibility reached a maximum during the fixing stage and then slowly declined with a relatively small change. Initially, the maximum force dropped down and then gradually elevated later.Both the tensile strength and the fracture strain indicated an upward movement at the beginning and then a downfall afterward. The elastic modulus changed little before the final panning stage, then raised significantly. The correlation analysis revealed that the flexibility of tea leaves was highly positively correlated with water content. At water content of 30% and 50%, the plasticity and flexibility of tea leaves reached a clear peak and the maximum force was at a low level, which is suitable for the shaping of Longjing tea. The results also demonstrated that the main mechanical properties of different tender materials change differently during the processing. The research findings can provide parameters for optimizing the mechanical design and processing technology of Longjing tea.