| Mulberry leaf which derive from moraceae mulberry plants(Morus alba L), has the function of blood enriching, evacuation wind hot and effect for liver ventilation. Mulberry leaf contains flavonoids and glucoside, alkaloids, polysaccharide, naphtha, different kinds of amino acids, trace elements, etc, besides traditional medicinal value, it still have the function of enhancing the body’s endurance, resisting decrepitude, antibacterial healthy, preventing and resisting cancer and lowering blood glucose,etc. The existing mulberry green tea has strong beany flavor after brewing, this flavor seriously influences on the palate; at the same time, the phenomenon of dark soup greatly reduce the sensory quality. How to process mulberry green tea which has the quality of pure flavor, bright and yellow-green soup, and can keep the functional component is of extremely vital significance. This paper is on the basis of green tea processing methods and study on raw mulberry leaf and its suitable system, different processing methods,UV-B treatment.The major findings are as follows:The ingredients of mulberry green tea exist significant difference in different picking time, Polyphenols, flavonoids and soluble proteins content increase with the increasing number of months. Sampes picked in November and December have higher content of functional components than other picking time. On the sensory evaluation, Samples picked in May and June have bright and green soup while the tasete is plain and beany flavor is strong. Sampes picked in November and December have good taste but the color is poor, beany flavor is strong,comprehensive analysis result shows that October is the best picking period of the mulberry green tea. Mulberry leaf green tea aroma analysis shows that Benzaldehyde,6-methyl-5-Hepten-2-one, β-Ocimene, Nonanal, Salicylic acid methyl ester, geranylacetone, β-Ionone, α-farnesene,etc are the main aroma components, including aldehydes, ketones, esters, alcohols and olefins.In order to research the process of reducing beany flavor and improving the color of tea soup, we select "raw materialsâ†'Spreadingâ†'Fixingâ†'Rollingâ†'Drying" as the main line,the results are as follows:3-6leaves are suitable for tea processing by comparison of different mulberry leaf contains of ingredients and utilization analysis.mullberry green tea’s suitable spreading time is9-10h, this result was obtained from the analysis of moisture changing,components changing and sensory evaluation during spreading time.Use single factor experiment and orthigonal test to determined the fixing time, fixing temperature,weight of leaves on pan-fried fixing, microwave fixing, blanching fixing and steam fixing.Sensory evaluation,POD enzyme inactivation and the effect of reducing beany flavor as the indicators of fixing effect, identify the best fixing technology are as follows. The optimal conditions of pan-fried fixing:fixing temperature180℃,fixing weight120g; The optimal conditions of blanching fixing:blanching temperature100℃, blanching time2.5min,fixing weight100g; The optimal conditions of microwave fixing:microwave temperature100℃,micro wave time2min,the weight120; The optimal conditions of steam fixing:fixing time2.5min, the weight100g. Using these conditions handled,fixing leaves acquired a high score of sense,POD enzyme which in leaves inactivated and the effectively reducing beany flavor. Fixing leaves’ main component of dry tea and soup color as the main indicators, combined with the sensory evaluation were analyzed and the results show that:The pros and cons of fixing leaf quality in turn as follows:microwave fixation> steam fixing>pan-fried fixing> blanching fixing.The analysis of rolling process rely on the indicators of components and color of tea in different pressure, results show that no pressure5min,middle pressure15-20min and the no pressure5min is the suitable rolling style of mulberry green tea.Compared fried drying,drying, drying combined with fried drying after, fried drying combined with drying after and microwave drying, the result show that two kinds of drying combined with fried drying have better aroma, beany flavor is light; microwave drying and drying of tea color is excellent while the aroma and taste is poor. The score of comprehensive evaluation about fried drying combined with drying after is higher than other samples.3. Two40W of UV-B lights were used as the light source, spreading leaves were irradiated at different time,β-glucosidase activity were studied in irradiated process. After irradiation, the components, aroma and sensory evaluation were analyzed, the results are as follows:During spreading,the activity of β-glucosidase in different treatment shows the trend of first increasing and then decreasing.The untreated sample’enzyme activity rich to the maximum of0.828Unit/g FW at9h,while The treated sample’enzyme activity rich to the maximum of0.872Unit/g FW at8h;the enzyme activity of treated samples are stronger than untreated samples in period of3～10h.With the irradiation time prolonged, the total flavonoid content of mulberry green tea increased very significantly; polyphenlos increased significantly; total chlorophyll content decreased significantly;other components have no significant change.The the total number of aroma in mulberry green tea treated by UV-B have more than untreated samples during the irradiation time of3-7h, the main type of increasing aroma is ester.On the aroma classification,with the irradiation time prolonged, Alcohols, ketones content decreased and esters content increased, Olefin content had the trend of "up-down-up" and treated samples were higher than untreated samples. Aldehydes had the trend of "down-up-down ".In individual components, Butyric acid-(Z)-3-hexene-ester, propionic acid-(Z)-3-hexene-ester,4-ethyl-Benzaldehyde, Butanoic acid, hexyl ester,etc only exist in treated samples; acetate-3-Hexen-l-ol,3,7-dimethyl-1,6-Octadien-3-ol, etc had the trend of "up-down "and riched the summit at5h;1-Octen-3-ol, Hexanoic acid, thio-, S-butyl ester,2-cyclohexene-l-one,etc had lower content than untreated samples; β-Ocimene, Salicylic acid methyl ester, a-farnesene,etc had higher content than untreated samples.Sensory evaluation result show that the treated time of4-5h is optimal, this treatment can reduce beany flavor to some extent and had no significant effect on tea soup. |
PDF Full Text Request