Optimization Of RAW Material And Processing Technology Of Instant Green Tea Powder

Nowadays,spring teas are the most famous species of green tea in Chinese tea consumption market.A lot of summer tea and autumn tea were waste because of their poor sensory properties and few consumer markets.The requirements of instant green tea powder on raw materials quality are much lower than that of famous green tea.Therefore,it is of great practical significance to select summer tea as raw material of instant tea powder from the view of economic benefits and resource utilization.In this paper,10 types of tea sample were collected from Pingli County,Ankang City,Shaanxi Provincein summer,autunmn and winter respectively.And the chemical constituents of tea leaching,such as tea polyphenols,amino acids,caffeine and soluble sugar,were measured and analyzed.For determining the proper picking month,the changes of these parameters in the tea were observed along with their growth phase.In addition,Longjing 43 dry tea leaves were used as raw material in the extraction process with vacuum-coupled ultrasonic auxiliary technology.The parameters in this process,like extraction temperature,extraction time,solid-liquid ratio,ultrasonic power and vacuum are optimized by single factor tests based on the results of leaching rate of tea polyphenols.On the basis of single factor experiment outcomes,the optimum technological conditions of this extraction method were confirmed by response surface optimization design experiment.For the spray drying process,the yield and tea polyphenol content were considered as the evaluation index.The inlet temperature,feed speed and the soluble solid content were involved in this study to optimize the instant green tea powder parameters of spray drying process.The results of this study are as follows:1?The biochemical compositions of the 10 samples in three seasons various significantly and show the different trend.The water content of the extract: autumn(40.11%)> summer(39.93%)> winter(37.19%),the content of tea polyphenols: summer(17.61%)> autumn(15.92%)> winter(11.09%),the amino acid mass fraction: autumn(2.78%)> summer(2.48%)> winter(1.70%),the content of caffeine: summer(4.22%)> autumn(3.72%)>winter(3.42%),the soluble sugar content: summer(4.04%)> autumn(2.83%)> winter(1.43%).In which the general trends of tea polyphenols,caffeine and soluble sugar in summer are larger than those in autumn,while the total trends of water content and amino acid massfraction are opposite.2?From the point of the chemical constituents,fresh tea leaves were higher than dried leaves,besides,one bud two leaves were higher than four pairs of leaves,Longjing 43 was higher than Pingli camellia,high altitude tea 1100 m Longjing 43 dry tea was higher than the low altitude Longjing 43 dry tea.That is,the tea chemical contents of Longjing 43 fresh leaves,Pingli camellia fresh leaves and,1100 m Longjing 43 dry leaves were richer than others.In summer and autumn,the chemical composition of 10 types tea leaves were richer than that of winter.Among them,the chemical composition of Longjing 43 fresh leaves,PingLi camellia fresh leaves and,1100 m Longjing 43 dry leaves were higher.Bases on the resource utilization and tea quality,these six kinds of tea are chosen for instant green tea powder production,winter tea is not suitable for this processing.3?The optimum extraction conditions of vacuum-coupled ultrasonic auxiliary technology are as follows: extraction temperature: 88 ?,extraction time: 20 min,extraction power: 49%(total power: 800 W),solid-liquid ratio: 1:28.Under this condition,the extraction rate of tea polyphenols reached to 11.04%.The influences of these factors the extraction rate of vacuum-coupled ultrasonic method were solid-liquid ratio > extraction temperature >ultrasonic power > extraction time.4?The influences of these factors on the yield of instant green tea powder were soluble solid contents > temperature > feed speed,the optimized drying technological parameters were: inlet temperature:170 ?,feed speed:700mL/h,soluble solid content: 25%.Under this condition,the yield of instant green tea powder reached to 23.11%.The influences of these factors on the polyphenols content of instant green tea powder were soluble solid content >inlet temperature > feed speed,the optimum drying technological parameters were: inlet temperature:170 ?,feed speed:700mL/h,soluble solid content:20%.Under this condition,the yield of instant green tea powder reached to 40.64%.