| With the rapid increase of labor costs of China’s tea picking and processing, mechanical tea-picking become the inevitable trend of enterprise scale processing, but apheresis fresh leaves’uniform homogeneous has difference, the overall quality is not high, and it’s processing has difficulty. This paper through the research of fresh leaves pretreatment processing, to facilitate the quality of fresh leaves, and to improve the quality of tea and the overall economic efficiency.In this paper, machine-plucking fresh leaves as raw material, the effect of the bulk tea grader grading system, fresh tea leaves’main chemical components and aroma changes when air conditioning spreading, heating withering, effect of different light sources and the best green sun conditions were systematically studied.The results obtained finally were as follows:1.The new grading machine is composed of a classification trough, a power trans-mission line, a rocker and a frame. The experiments showed that when the second batch of fresh leaf material was treated, and with a feed rate5kg/min and vibration frequency50Hz, the average classification rate was as high as79.04%, and materials caught in the net was3.60%. Above all, it is a machine which can effectively realize the classification of the machine-plucked tea leaves.2.Under different spreading condition,during0to8hours,at room temperature,22℃conditions, moisture content decreased faster; Under different spreading condition, tea polyphenol content decreased, amino acid content increased, ratio of tea polyphenols to amino acids decreased, water extracts increased.caffeine content increased and then decreased under room temperature spreading, other conditions rose; At room temperature,the amount of total catechins and tea polyphenols were in the same variation trend,under22℃、25℃condition, total catechins showed a trend of increase and then decrease, total catechins showed a trend of increase and then decrease and increase under28℃.The air conditioning spreading was conducive to the holding of the total catechins;Spreading was conducive to the increase of aroma substances which were significant contribution to the tea aroma such as α-farnesene, benzyl alcohol, phenethyl alcohol, linalool, linalool oxide Ⅰ, Linalool oxide Ⅱ, cedrol, geranyl formate, methyl salicylate, dihydroactinidiolide, indole. But laying it for too long, the content of aroma substances was decreased.This trials compared test on some factors as the spreading temperature,spreading time,spreading thickness.The product was manufactured by the process of Hongqing green tea, The datas were analyzed through sensory evaluation, physical and chemical analysis,The results showed that, three factors on the tea quality influence order was spreading time,spreading temperature,spreading thickness.The best combination of spreading process was28℃of spreading temperature,6h of spreading time,15cm of spreading thickness. Under these conditions, the tea polyphenol content was low, amino acid content was high, ratio of tea polyphenols to amino acids was low, water extracts was high, the total simple catechins was high.3.Under heating withering condition, fresh leaves lost water faster, and was fast-slow-fast trend.40℃water loss was the fastest, followed by36℃,32℃,room temperature withering was the slowest.Contents of tea polyphenol took on diverse course during different temperature withering. Contents of tea polyphenols reduced at first,then increased during withering with room temperature and36℃,however it increased in the beginning,then decreased under32℃、40℃withering.Content of amino acid increased at first,then reduced with room temperature、36℃and40℃withering.But it gradually increased under32℃withering.Content of caffeine reduced at first,then increased during withering with room temperature withering.it increased at first,then reduced under32℃withering,it gradually increased under36℃withering,it did not change significantly under40℃withering.Ratio of tea polyphenols to amino acids reduced at first,then increased during withering with room temperature,it gradually reduced under32℃and36℃withering,it increased in the beginning,then decreased under40℃withering. Content of water extracts increased during withering room temperature、32℃、36℃and40℃. Total catechins increased at first,then reduced under room temperature、32℃and40℃withering.it decreased in the beginning,then increased during withering36℃.When withering leaves’water content was about60%,the withering leaves had the best quality under36℃. Tea polyphenols fell by4.18%than not wilting leaves, total amino acids increased by2.12%, caffeine decreased by2.34%, ratio of tea polyphenols to amino acids fell by6.08%, water extracts increased by3.54%, simple catechins decreased by7.81%, complex catechin fell by5.88%.When withering leaves’water content was about70%,the withering leaves had the best quality under36℃. Tea polyphenols fell by2.21%than not wilting leaves, total amino acids increased by6.88%, caffeine increased by5.59%, ratio of tea polyphenols to amino acids fell by8.53%, water extracts increased by1.70%, simple catechins decreased by5.21%, complex catechin fell by1.02%.Miscellaneous oxygen was lower than not withering leaves, Hydrocarbons, ketones, aldehydes, acids, alcohols, esters, indole were higher than those not withering leaves.4. The infrared light source and xenon light source in different heights irradiation30min,tea polyphenols, total amino acids, ratio of tea polyphenols to amino acids, water extracts were no significant difference with sunlight, caffeine content was difference with sunlight, The aroma substances kinds were slightly less than the sunlight. The total amount of aroma substances were small differences between xenon lamp irradiation and sunlight.The best combination of simulated solar withering process was xenon lamp irradiation,irradiation height50cm,irradiation time50min. Under these conditions, the fresh leaves’tea polyphenols content was low, amino acid content was high, ratio of tea polyphenols to amino acids was low, total catechin was moderate, ratio of complex catechins to simple catechins was low. Aroma substances hydrocarbons, such as alcohols, ketones, aldehydes, esters were high,the withering leaves’comprehensive quality was optimal. |
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