Application Of Enzymic Treatment And Modern Technologies To The Process Of Pu-erh Tea Cream

In this study,the application of different kinds of exogenous enzymes and modern technologies in the process technology of Pu-erh tea cream was studied based on the sun dried green tea of Yunnan big leaf,and the process technology of Pu-erh tea cream was also optimized.The purpose of this study was to provide fundamental basis for high quality of Pu-erh tea cream.The process technology of Pu-erh tea cream was firstly optimized by orthogonal test based on contents of characteristic chemical components in tea cream and its sensory feature,besides,changes of major chemical components during concentration were also studied.The optimum process technology conditions were as follows: the ratio of water to raw material 1:20(g/ml),extraction temperature 80 ?,extraction time 35 min and concentration temperature 100 ?.Under these conditions,the extraction efficiency of all chemical components in Pu-erh tea cream was highest and its sensory evaluation was relatively high.During concentration of Pu-erh tea cream,the content of tea polyphenols and amino acids decreased,and that of theaflavins and thearubigins increased firstly then decreased,while content of theabrownins kept increasing constantly.Based on the changes of contents of amino acids,tea polysaccharides and tea polyphenols,effects of different enzymatic treatments on the contents of major compounds in Pu-erh tea cream were studied,conditions of different enzymatic treatments were optimized and the sensory characteristics of different tea cream were also evaluated.Results showed that in the same enzyme dosage,hydrolysis efficiency of flavourzyme was significantly higher than that of neutrase(p<0.01),the increase rate of amino acids was 28.49% and 15.19% respectively.Under the condition of 27 U/g complex proteases,two kinds of proteases had the best synergistic effect,which was higher than that of single enzyme(p<0.01)and the increase rate of amino acids was 22.07%.Moreover,the ability of different carbohydrase to hydrolyze tea carbohydrates was ranked as follows: viscozyme > pectinase > cellulast,and the difference among them was significant(p<0.05).After the treatment of viscozyme,the increase rate of tea polysaccharides was 82.45%.However,polyphenol oxidase had little effect on the transformation of tea polyphenols whose content decreased from-0.20% to-4.55%.The hydrolytic time,the concentration of flavourzyme and the concentration of viscozyme were selected for central composite design(CCD),response surface methodology was applied in the extraction of Pu-erh tea cream based on the response values of contents of amino acids and tea polysaccharides.Results showed that there was interaction among hydrolytic time,the concentration of flavourzyme and the concentration of viscozyme while the interaction between the concentration of flavourzyme and the concentration of viscozyme was mainly significant.The best technical parameters were obtained as follows: hydrolytic time was 5.14 h,the concentration of flavourzyme was 53.55 U/g and the concentration of viscozyme was 80 FBG/g.Under these optimized conditions,the effect of composite enzyme was higher than that of single enzyme.The aroma profiles of the optimized Pu-erh tea cream were then studied by simultaneous distillation extraction(SDE)combined with gas chromatography-mass spectrometry.Results indicated that the key aroma components in the optimized Pu-erh tea cream were the alcohols(floral and fruit smell),the furans(furanones)and the nitrogenous compounds(caramel-like smell),which was similar to that of raw material.The differences were displayed by the decrease in number of the aroma compounds,the disappear of alcoholic compounds with green grass smell,as well as the increase in contents of furans(furanones)and nitrogenous compounds.Water bath concentration and vacuum concentration were employed to optimize the concentration process technology of Pu-erh tea cream.Results showed that the content of major chemical components in Pu-erh tea cream produced by vacuum concentration was higher than that of water bath concentration and its sensory quality was also better than that of water bath concentration.Besides,Hot air drying,vacuum drying and freeze drying were applied to the drying process technology of Pu-erh tea cream and the effect of different drying methods on the aroma profiles of Pu-erh tea cream was also studied.The results showed that freeze drying had least effect on the nutrition constituent of Pu-erh tea cream,followed by the hot air drying and vacuum drying.The sensory quality of Pu-erh tea cream produced by hot air drying and freeze drying was relatively high,but the difference among drying methods on sensory quality was not significant.The aroma profiles of Pu-erh tea cream produced by hot air drying and freeze drying were similar to that of raw material,while the aroma profiles of Pu-erh tea cream produced by vacuum drying were different from those of produced by other two drying methods.