| Wuyi frozen tea has special flavor and qualities ,and contains more water than traditionally drying tealeaf. It was easy to be contaminated by microorganism, and had to be put under frozen condition for storage. For the purpose of prolonging the shelf-life of Wuyi frozen tea during cold-storage by decreasing the total count of microorganism, light microscope and PCR techniques was used to definite the main microbiological species in the tea,and UHP was used to kill the microorganism for choosing the optimal parameters of sterilizing .The killed-microorganism mechanism of HPP and the influences of HPP to the qualities of frozen tea were also studied in this paper. The results were showed as follows:1.Analysis of microbiological species: During 0-4℃storage for 15days, the microorganisms in the tea was analyzed.Results showed that the amount of microorganism in the tea was low and, mold and yeast breeding quickly. By biomorphology analysis, during 0-4℃storage, mold in the tea mainly contained aspergillurm,mucor,rhizopus,penicillium and some unidentified microorganisms. Yeast mainly consists of white yeast and red yeast by color identify. Aspergillum and white yeast were dominant species in frozen tea during cold-storage.2.Strain identify: The DNA of the unknown main mold and yeast were extracted, and the amplification and sequencing of PCR was used to its ITS region. The results showed that the main microorganism in the tea were Penicillium·crustosum Thom and Debaryomyces hansenii.3. UHP factors analysis: The influence of UHP pressure and time on the Penicillium·crustosum Thorn and Debaryomyces hansenii were significant (p<0.01). With the increase of pressure and processing time, the growth of Penicillium·crustosum Thorn and Debaryomyces hansenii showed an inverse correlationship. Adopted the measure of quadratic regression of orthogonal and rotational combination ,the model of factor were regressed to describe the effects of UHP on processing . The numerical measure of predominant cultures was correlated to press and time.The regression model were established as following equation: Y=1.365-1.062X1-0.862X2+0.355X12+0.385X22.With testing and verifying the feasibility of the equation, the results showed that the regression model could used to control the numerical measure of predominant cultures.4.Sterilizing of UHP: After SEM observation of microorganism in the tea after UHP processing and measuring the NA and PR value by UV absorbing method, the results showed that UHP made the cell wall of predominant cultures shrinked, breached and leaked out cytoplasm ,and at last caused the death of microorganism. 5.UHP processing technology: Microorganism, the sense-organs and physical and chemical index were used for the target to ascertain the optimal HPP technology. The results showed that : 20℃for 15min under 500MPa, the tea could be storied for 3 months safely,and UHP processing technology had non-significant effects on frozen tea qualities indexes. |
