Study On The Light Compensation Technology Of Congou Black Tea In Withering Process

Withering is the first process in the manufacturing of the black tea and the most critical step to ensure its quality. With the time lasting and environmental factor variations, a series of physical and chemical changes have happened in fresh leaves. Light is one of the important factors about withering process and the study about this is lack. In order to investigate the effects of red light and blue right for withering of black tea, the respiratory rate,the contents of soluble sugar, flavonoids,amino acid and catechins of the withering leaves,were evaluated.Setting three different withering light of quality, intensities, time, the sensory evaluation, main biochemical components, tea pigments of made tea were evaluated. Next,the study propose a set of congou light compensation withering technical parameters for Zhejiang tea area. Based on this, the study predict the model of changes on water content of leaves and provides a effective method to objective detect water content of leaves in withering process.The experimental results were as follows:1.In order to investigate the effects of red light and blue right for withering of black tea, the respiratory rate,the contents of soluble sugar, flavonoids,amino acid and catechins of the withering leaves were evaluated.(1)The results showed that with the increasing of withering time, the total of amino acid and the most content of amino acid increased gradually, except Asp and Thea. Asp and Thea of the red light withering leaves had decreased more than others, and Ile, Leu, Tyr. Lys, His had increased more. Ser, Val, Phe of the no light withering leaves had increased more than others. Other contents of amino acid of the blue light withering leaves had changed most.(2) GC, ECG, total esters type catechins and total catechins decreased gradually. C, GCG, CG, EGC increased at beginning and then decreased during withering, EG decreased at beginning and then increased during spreading, and they were increased than fresh leaves. ECG, EG, GCG of the blue light withering leaves had changed more than others, and other contents of catechins of the red light withering leaves had changed more than others.(3)The released the contents of soluble sugar increased first, then decreased. The contents of soluble sugar of the biue light withering leaves had decreased more than others, and red light decreased secondly.(4)The amount of flavonoids has deceased by withering process, and showed the following rule: blue light>red light>dark.(5)the respiratory rate in different has the maximum value in 5h during withering process, and showed the following rule: blue light>red light>dark.2. with different light withering process, the selected light source were: white,yellow, blue, red, setting a processing without light treatment as the contrast. The results show that different light quality withering has a significant impact to the sensory evaluation, and the store of red light is highest. According to the results of yellow light, red light, white light treatment of tea polyphenol, flavonoids, caffeine are significantly higher than contrast, and soluble sugar and amino acid content is less than contrast. Amino acid, flavonoids and soluble sugar content of blue light withering treatment is more than contrast, with caffeine and tea polyphenol is less.The single red light was used to withering tea leaves, and three light intensities of 1000 lux,2000lux,3000 lux were setted. The results showed 2000 lux treatment has the highest sensory evaluation store(88.9). And the chemical test showed that, the contents of tea polyphenol, catechins,TRs,TFs of 2000 lux treatment were less than others, and amino acids, soluble sugar content were more.The single red light was used to withering tea leaves, and three light illumination time of 12 h,no light with 9h,9h light without light were setted. The results showed no light with 9h red light treatment has the highest sensory evaluation store(89.85),and amino acids, soluble sugar content,TRs,TFswere more than others. The study propose a set of congou light compensation withering technical parameters for Zhejiang tea area.3.To study the effect of temperature on water content of leaves in light compensation withering process of Congou black tea to predict the model of changes on water content of leaves. Basic models were developed for 4 temperatures(20℃, 25℃, 30℃, 35℃) and 60%-65% relative humidity(RH), that cleared the correlation of time, temperature and leaf water losing rate of the withering. Obtained the prediction model of relationship between fresh leaf water losing rate and temperature based on chemical reaction kinetics and Allen equation(Arrhenius)(R2>0.98). An experiment was done to verify correctness of the model showed that the predicted values achieved from the model agree well with field test results(P<10%). Leverage the model to forecast the law of water losing rate of leaves and determine the time ranges of wilting, that had important theoretic value and guiding signification for the withering of congou black tea.4. The detect method of water content is established based on computer vision and appearance difference meter, through step regression analysis. Results showed that related indexes of detect method based on computer vision are exploed, with determination coefficient(R2) is more than 0.999. An experiment was done to verify correctness of the model showed that the predicted values achieved from the model agree well with field test results(P=3.99%). This study provides an effective method to objective detect water content of leaves in withering process.