Study On The Change Of Physical And Chemical Properties And The Evaluation Method Of Twing Rate During Rolling Process Of Congou Black Tea

With the rapid development of the tea market in recent years, congou black tea gets the favour of consumers gradually, as the the peculiar black tea for china and enjoying a high reputation in all over the world. Rolling is the key process in the manufacturing of the congou black tea, and provides the necessary material foundation for subsequent processing, and play a important role to ensure its quality. In my study, the basic physical properties, appearance texture, mechanical properties, electrical properties, optical properties, microscopic structure and main chemical composition of rolling articles being processed of congou black tea rolling process will be researched, and the evaluation methods would be established based on information fusion from correlation analysis.At the same time, pressure acquisition device during rolling process of congou black tea was designed, the real-time pressure of rolling lobe group were collected based on the schedule pressure, and the automatic pressure rolling equipment were designed. The experimental results are as follows.1. The activity of PPO was reduced with rolling time and will increase slightly after40min, and the activity of POD was reduced gradually during the rolling process. The voltage to alcohol group aroma increased with rolling time, and the increase amplitude was larger in the first15min. Catechin component C showed increased slightly and the rests of component content decreased, the change of EGCG and EGC content was relatively large, especially. The change of TFs content showed slightly increased, but the content of TRs was from0.1%to3.5%and from1.5%to3.1%of TB.2. The relationship between volume-weight and rolling time was similar to cubic function, and the coefficient of determination above0.9. Twig rate showed unimodal curve with the extension of rolling time and the peak time around25min, the change tendency of stretch tea rate was reduced but broken tea rate was increased. The change tendency of average circumference and mean area of appearance texture was gradually decreased with prolonged rolling time, and the coefficient of determination of fitting curve with rolling time was above0.9. The plastic properties and softness properties showed unimodal curve with prolonged rolling time and the peak time was around25min, the corresponding maximum form variables were7.68mm and19.47mm, but flexibility properties with rolling time was linearly reduced. The electrical characteristics parameters Cp and D was gradually increasing with rolling time, but Lp,0, Z,χ, R and Rp was gradually decreased, and the imitative effect was also good between electrical characteristics parameters and rolling time and the coefficient of determination above0.9.3. The exterior color and luster of rolling articles being processed was slowly from green to dark green, to yellowish-green, to reddish-green and to light reddish brown, It wasn’t obvious and stabilized for color parameter R and B, and the color parameter G,2G-R-B, HUE, Hab*was gradually reduced with prolonged rolling time but R/G was increasing. The microstructure studies of rolling articles being processed had shown that the mesophyll cells of withering leaves were relatively discrete but the chloroplast structure was relatively intact. The chlorophyll would be released from protein to inside the cell or clearance when rolling to5min. As rolling continued, the histocyte porosity appears decreased gradually, the organize appeared lattice mismatch, the spongy tissue cells appeared disordered arrangement, the epidermal cells appeared crease, the palisade tissue cells appearec tilt and distorted, and the epidermal cells of rolling leaves would appear wear and even broken when rolling to55min.4. The study showed that twig rate had a good correlation with the corresponding physicochemical property through correlation analysis. Based on this, the regression equation was established for twig rate, based on volume-weight, physical parameters (removal of volume-weight, stretch tea rate and broken tea rate), chemical parameters and information fusion that includes color parameters, texture parameters, electricity characteristic parameters and alcohol group aroma. These equations were, Y=-104.407-0.661*X+0.001*X2,R2=0.918;Yi=421.326-124.515*color parameters R-3.573*HUE-0.108*average circumference+2.864*Cp-18.006*D+4.086*electricity characteristic parameters R, R2=0.996; Y2=-175.465+50.219*C+28.667*EC-235.616*TFs+18.224*TRs+52.134*TB, R2=0.989; Y3=358.646-156.261*(2G-R-B)-3.173*HUE -0.097*average circumference+3.167*Cp-18.321*D+4.5657*electricity characteristic parameters R, R2=0.996, respectively.5. The real-time pressure presented undulation during the light precess, medium pressure, heavy process of rolling process because of the floating pressure and testing delay. According to the set pressure mode, the average of real-time pressure of rolling process showed that the first stage was1.56kg,1.92kg,4.05kg,12.36kg, respectively, the second stage was0kg,0.61kg,6.21kg,14.26kg, respectively, and the third stage was Okg,0.52kg,4.48kg,15.72kg, respectively.