Study On Taste Improvement For Green Tea In Summer And Autumn

With materials of single bud and one bud and two leaves plucked by hand in summer,and two or three leaves plucked by hand and three or four leaves plucked by machine in autumn,content variations of water extract,tea polyphenol,catechin, flavone,anthocyanin,amino acid and caffeine in tea samples of spreading treatment and some raw teas under conditions of regulating temperature and humidity are determined to study spreading technologies that improves tastes of teas in summer and autumn.It shows that,content variations of polyphenol,catechin,flavone and anthocyanin are connected with tendemess and water extract and caffeine increase; amino acid in single bud first increases and then decreases,the proportion of phenol to ammonia(P/A) descends and the proportion of simple catechin to ester catechin (S/E) first descends and then ascends,the tea sample which is spread for 12.5h at 21-24℃and 55-65%gets top score for taste evaluation;while amino acid in one bud and two leaves increases,P/A first ascends and then descends and S/E descends, the tea sample which is spread for 7.5-10h at 25-27℃and 60-70%achieves the best quality.Polyphenol,catechin,flavone and anthocyanin in two or three leaves in autumn change obviously,amino acid first decreases and then increases and P/A first ascends and then descends,the tea sample which is spread for 4-10h at 18-21℃and 55-70%and rotated three times for 5.5-9 minutes is thought the best.For spreading treatments of three or four leaves plucked by machine in autumn,with increases of rotating intensity,water extract,polyphenol and catechin tends to decrease,amino acid first increases and then decreases to below CK,P/A first decreases and then increases,while content variations for taste substance in raw teas are different from those above,at 18-20℃and 75-80%three or four leaves should be spread for about 18h and rotated slightly three times for 6-7 minutes.Three batches of different tendernesses of summer raw tea which are green and astringent are used as materials and contents of each taste component in teas which are baked at 100℃(for 5 hours,every one hour),120℃and 140℃(for 2.5 hours, every half an hour) are determined to study suitable baking technologies.It shows that,water extract in tea of one bud and two leaves baked at 100℃and 120℃decreases,polyphenol and amino acid at three temperatures all reduce,P/A tends to cut down at 100℃while goes up at 120℃and 140℃,flavone first decreases and then increases at 100℃and 140℃while that is just opposite at 120℃, anthocyanin increases at 100℃and 140℃,caffeine decreases at 100℃,and the better baking parameter combinations are as follows:100℃/3h,120℃/1.5h和140℃/0.5h.Water extract,polyphenol and catechin in single leaf reduce at 100℃and 120℃,at 100℃amino acid and P/A change fluctuantly,S/E ascends,and caffeine decreases while at 120℃amino acid decreases,P/A first cuts down and then goes up, S/E initially ascends and later descends,flavone first decreases and then increases, anthocyanin reduces,and the better combinations are as follows:100℃/2-3h(tea of tender single leaf) or 100℃/4h(tea of coarse single leaf) and 120℃/1b.