| It has been reported that raspberry leaf show a lot of health function such as hypoglycemic,antioxidant,anti-inflammatory,anti-thrombotic and so on,therefore, raspberry leaf become a kind of tea can be a good way to make full use of raspberry leaf and broaden Chinese tea market. Based on the suitability of raspberry leaf, we follow the green tea processing to make raspberry tea and used the leaves of Heritage as materials, studied withering processing, enzyme deactivation processing and drying processing. The change of color, aroma and composition contained in the leaves during processing was researched in this paper. The main results are as follows:1. To detect the main composition (amino acids, water extracts, polyphenols, soluble sugar, flavonoids) and do sensory evaluation in the samples which were made in the different withering processing, on comprehensive judgment, we found that the suitable withering time is3h.2. Based on the deactive enzyme methods in China,Guochao heating technique,microwave heating technique,steam heating and blanch heating technique were taken in this paper,on the comprehensive judgment,microwave heating technique was the best.3. According to the single factor, three levels of each factor were selected and then design orthogonal test, the relative activity of POD and leaves sensory score were indicators. At last, the result showed that the best condition of deactive enzyme was obtained with application of microwave power of640W, microwave time for60s, raspberry leaf50g.4. Hot-air drying, infrared drying, microwave drying and vacuum freeze drying were taken afer rolling processing. Summarizing the results of intrinsic quality and sensory score, the quality of raspberry leaf tea made by microwave drying was the best.5. According to Mixture design in Minitab, taking sensory evaluation as indicators and make it combined with fuzzy comprehensive evaluation sensory method, the prediction model was bulit as follows:Y=6.48A-15.49B+1.92C-44.86D+29.41AB+5.32AC+61.63AD+33.40BC+100.26BD+94.16CDAt last, the optimal formula was made:raspberry leaf ratio of0.60, green tea ratio of0.11, the hawthorn ratio of0.18, and the Chrysanthemum ratio of0.11.6. The changes of raspberry leaf color during processing were as follows:In the process, the value of L has been decreased, but the absolute value of b/a has been increased, this indicates that the color of raspberry leaf become yellow gradually, and leading to ultimately the formation of a yellow-green color quality.7. The changes of the main intrinsic quality ingredients during processing:Water extracts,amino acids and soluble sugar content trends consistently,that is,the content is increasing during withering processing and rolling processing and decreasing during deactive enzyme Processing and drying processing. The content of polyphenols and flavonoids in raspberry leaf tea processing has been a decreasing trend.8. The change of aroma during raspberry leaf tea processing was complexed, because the kinds of aroma and the ratio between different aroma substances were constantly changing, it ultimately given the unique aroma of raspberry leaf tea. The content of D-limonene, neral, Myrtenal, geraniol,(E)-citral,(E)-2-Hexenal, D-citronellol, linalool, benzyl alcohol,2-n-pentyl furan, β-ionone is higher and they become the main aroma substances in raspberry leaf tea. |
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