Study On Technique For Biological Fresh-keeping Of Oolong Tea

Oolong tea Tie Guanyin was selected as the research object. According to the mechanism of the quality deterioration of Oolong tea as well as property of keeping aromatic substances and oxygen exclusion by pullulan membrane, a technique for developing pullulan membrane used for Oolong tea fresh-keeping was researched in this paper. The experimental results were as follows:(1)The result of sensory evaluation showed that after 6 months of storage period(from June 2010 to December 2010), the scores of appearance, liquor color, aroma, taste and infused leaf of Tie Guanyin obviously reduced and sensory scores of Tie guanyin decreased by 31.3%.Testing results of the chemical compositions showed that the respective variation of different chemical compositions had their own way. The reduction rate of chemical composition contents were as follows: water soluble(23.6%)> chlorophyll(22.1%)> amino acids(18.3%)> tea polyphenols(11.7%)> caffeine(5.8%).(2)In use of statistical methods, a mathematical model was established on a relationship between quality scores and biochemical compositions, Y( quality score) =-109.928+2.886X1(extract)+ 0.635X2(TP). The results of significance test and fitting test showed that in the storage condition of room temperature, quality deterioration degree of Oolong tea Tie Guanyin could be judged by changes of tea polyphenols and water extract content.( 3) According to the principle of chemical dynamics, in use of Q10, a single factor experiment was taken for a technique of developing pullulan membrane.The result showed that the temperature of pullulan coating agent(A), the concentration of pullulan coating agent(B)and drying temperature(C)had a significant effect on the technique of developing pullulan membrane(P<0.05). The relationship of three factors on the effect of tea polyphenols content was like this: drying temperature > the concentration of pullulan coating agent > the temperature of pullulan coating agent. Ultimately the process parameters were that the concentration of pullulan coating agent was 1.2%, the temperature of pullulan coating agent was 4℃ and drying temperature was 106℃.(4) The research about storage effect of different packing materials( HDPE,BOPP/PET/CPP, Tin cans)on coating Tie Guanyin showed that both physically and chemically coating Tie Guanyin were better than the control group. The results of significance analysis showed that there was a significant difference between coating group and CK group for three kinds of packaging materials at P<0.05. On the basis of pullulan coating process, selecting tincans as the packaging material of Tieguanyin tea could obtain good preservation effect.(5)The research about storage effect of different temperatures on coating Tie Guanyin showed that both physically and chemically coating Tie Guanyin were better than the control group. The results of significance analysis showed that in terms of tea polyphenols, caffeine,amino acids, chlorophyll and water soluble, there was a significant difference between coating group and CK group at 0.05 level except caffeine and chlorophyll in room temperature condition.And in the condition of 4℃, there was a significant difference between coating group and CK group at 0.05 level except water soluble.