Study On Processing Technology Of Mulberry Green Tea

Mulberry cultivation is very popular in China. Over-supplied mulberry leaves can be processed into mulberry tea, it’s an important way to promote sericulturist’s income and efficiency of agriculture. At present, thick taste, low, stuffy and nausea aroma were the main problem of mulberry green tea in market. In this research, suitability of fresh leaves for mulberry green tea making and its processing technology were studied, in order to find out the most suitable fresh leaves to making mulberry green tea and the optimum process parameters, which provided theoretical basis for practical production. The main results were as follows:1. Optimization of flavone test conditions of mulberry green teaIn this trial, the temperature, extraction solvent, developer dosage, developing time and detection wavelength for extraction and determination of flavone were optimized. The results showed that the best extraction temperature was 80℃, the best concentration of extraction solvent was 80 %, the best developer dosage was 4 ml, the best developing time was 20 min and the best detection wavelength was 391 nm.2. Study on suitability of fresh leaves for processingIn this article, the influence of mulberry variety, maturation, season, germplasm on the quality of mulberry green tea was analyzed systematically. The results showed that:Great differences of tea quality could be found among 67 different varieties. Among them, number 4, 16, 50, 20, 13, 23, 52, 60 are better in organoleptic quality and component contents, which were ideal varieties to make mulberry green tea.Young leaves were suitable for the manufacturing of mulberry green tea. With the leaf tenderness decreasing, the content of amino acids decreased and the content of soluble sugar and chlorophyll were increased. Flavone content of mulberry green tea made from young leaf were higher than that from old leaves and leaf bud. The mulberry green tea which made from old leaves showed poor quality with low aroma and tasted thick and stuffy.The most suitable season in a year for mulberry green tea making was summer, secondly spring. With the postponement of the growing season, amino acids and chlorophyll content were increased first and then decreased, while soluble sugar content showed a downward trend, and flavone of mulberry green tea which was made in spring was significantly higher than that in other seasons. Organoleptic quality analysis showed that green degree of dried leaves and infused leaves decreased with the postponement of the growing season. Aestival mulberry green tea which had pure and high aroma, fresh and mellow flavor was better than that made from fresh leaves in other seasons.3. Research of processing technology of mulberry green teaThe results of research on different de-enzyming ways (roasting de-enzyming, streaming de-enzyming, microwave de-enzyming, boiling water de-enzyming). Indicated that the main biochemistry components such as amino acids, soluble sugar, flavone and chlorophyll in roasting de-enzyming and microwave de-enzyming treatment were higher than in streaming de-enzyming and boiling water de-enzyming treatment. In addition, there were some bad smell in streaming de-enzyming of mulberry green tea and stuffy taste in boiling water de-enzyming of mulberry green tea. Optimization of the de-enzyming ways were roasting de-enzyming and microwave de-enzyming that made the mulberry green tea have higher aroma, and fresh, mellow flavour. On the basis of different de-enzyming ways, a roasting de-enzyming machine 6CST-40 was used to de-enzyming and to optimize de-enzyming temperature and time. Random design experiment was adopted to research the influence of de-enzyming temperature (100℃, 120℃, 140℃, 160℃, ) and time (25 s, 40 s, 55 s) on the quality of mulberry green tea. The results showed that at low temperature for short while, the de-enzyming was inadequate which made the peduncle red and taste thick. The main biochemistry components including amino acids, soluble sugar, flavone and chlorophyll were increased first and then decreased as de-enzyming temperature boosted. With de-enzyming time prolonged, amino acids, flavone and chlorophyll were increased except soluble sugar. Combining character and organoleptic quality, the best technology parameter were that the best de-enzyming temperature was 140℃and the best de-enzyming time is 55s.Research on rolling technics: influence of different rolling time (0 min, 5 min, 10 min, 20 min, 30 min, 40 min) on the quality of mulberry green tea was also studied. The results showed that mulberry green tea without rolling is better than those rolling ones in quality. The longer the rolling time was the worse the tea quality was. Tea quality declined tardily before 10 min and quickly after 10 min, so the suitable rolling time was within 10 min.Research on shaping technics: Two-pan quhao roasting machine was applied for shaping procedure of mulberry green tea. Orthogonal design experiment was used to study the influence of shaping temperature (120℃, 150℃)、leaf weight (1.5 kg, 2.5 kg) and water content (32 %, 40 %) on the quality of mulberry green tea. The results showed that the influences of shaping temperature and leaf weight on quality of mulberry green tea were significant, but the influence of water content was less significant. The high shaping temperature was good for the accumulation of a minoacids. polysaccharide tended to hydrolyze under high water content which need longer shaping time. The low shaping temperature and high water content induce shaping time became longer that were not benefit to maintenance of chlorophyll. Furthermore, the quality of tight and round appearance was not easy to be formed at fewer leaf weight, but vapor was not easy to be dissipated at more leaf weight, which lead to dull and yellow colour of tea liquor. Synthetically, optimization of the shaping condition was as follow: shaping temperature 150℃, leaf weight 2.5 Kg and water content 40 % of fresh leaves.Research on aroma-Enhancing: randomized trials were used to study the two aroma-Enhancing factors that were temperature (110℃, 130℃, 150℃) and time (1 min, 3 min, 5 min). The results indicated that high temperature and short time were propitious to the accumulation of amino acids. When the temperature was too high, the degradation of flavone and chlorophyll aggravated. When the time is too long, decomposition of soluble sugar and chlorophyll increased. Combining biochemistry components analysis with organoleptic quality analysis, the best temperature of aroma-Enhancing was 130℃, time was 3 min. As a result of the interaction of temperature and time, mulberry green tea contained more components at 150℃3 min and 130℃3 min.