Research And Application On Physical Properties Of Tea Leaf Material

In this paper, the basic physical properties, electrical properties, optical properties and mechanical properties were chosen as the main test parameters. It studied the physical properties of fresh tea leaf preliminarily and fundamentally, which plays an important role in classification of fresh tea leaf and tea processing. The main contents and conclusions are as follows:(1) Length, width and weight of fresh tea leaves showed an increasing trend with maturity increased, the fifth leaf of which slightly reduced; Length and weight of large-leaved species were significantly greater than other lobular species within 5 varieties of fresh tea leaves. Leaf area and weight increased rapidly with length increased.(2) Nondestructive inspection technology was applied to the determination of the dielectric property with LCR-bridge. The best testing condition was determined as:50 kHz,1.0 V. Under this condition, it analyzed the relationship between the dielectric property and variety, leaf position, freshness, moisture content of fresh tea leaves; A comparison on dielectric characteristic parameters between healthy leaves and other impurities was conducted as well. The experimental results showed that a significant difference between varieties; Capacitance and permittivity showed an increasing trend with tenderness decreased, especially in older leaves. While, capacitance and permittivity showed a decreasing trend with moisture content decreased; Capacitance and permittivity of fresh tea leaves injured were significantly higher than those of normal leaves.(3) Using the ASD FieldSpec 3 spectrometer to acquire and analyze the spectral reflectance data of fresh leaves of different varieties, different leaf positions, different moisture contents. The results showed that:the spectral reflectance curves of different varieties of tea fresh leaves are the same, as well as different leaf positions.In the near infrared region, there was a significant difference between reflectivity and the variety. Reflectivity showed an increasing trend with tenderness decreased. While, reflectivity showed a decreasing trend with the moisture content decreased. At the same time, using tristimulus colorimeter to compare chromatic values of fresh tea leaves, made sure the basic color range. The results showed that L* value and b* value of the fresh leaf tended to reduce with the tenderness decreased, especially in older leaves. While a* value showed an increasing trend with tenderness decreased, especially in older leaves. It showed that compared to old leaves, the color of tender leaves tended to be lighter, yellowish, greenish. Statistical analysis showed that the chromatic values significantly changed as the tenderness of fresh leaves changed, while there was no significant effect on chromatic values of varieties.(4) The basic research and experiment on tensile properties of fresh tea leaves was introduced briefly. The study analyzed the changing trend of force-displacement, force-time and stress-strain. Besides, the maximum load, the tensile strength, elastic modulus and other mechanical data of fresh leaf were obtained. The results showed that: the tea fresh leaf belonged to the plastic material. It had good elasticity and certain strength. Plasticity and flexibility of large-leaved species are better than other lobular species; which decreased with tenderness decreased. Therefore, different tea processing technology can be applied in the tea processing according to differences in mechanical properties. It is more conducive to the development and utilization of fresh tea leaves.(5) Through the determination of basic physical properties of the fresh tea leaf, a classifier was developed and detected successfully. The results showed that:The classifier based on the basic physical properties had the ability to complete the classification and obtain uniform fresh leaf materials. Under the condition of 9 r/min,0.83 kg/min, the effect of the classification is the best; Using the color sorter for sorting of fresh tea leaves, the impurity removal rate reached 90.89%, which could achieve the purpose of removing impurity.