Research And Effect Evaluation On Improving Flavor Quality Of Instant Jasmine Tea Powder

At present,instant tea powder has some problems,such as low fragrance,weak taste and poor solubility,so it is difficult to meet the needs of consumers.In this study,essential oil was used as raw material,saturated water solution method and vacuum freeze-drying method were respectively used to carry out microencapsulation experiments,and the embedding methods and process parameters with high embedding rate were screened to provide reference for the embedding of essential oil of jasmine tea.The essential oil of jasmine tea was extracted by water distillation and its extraction parameters were explored.The essential oil of jasmine tea was microencapsulated and its basic physicochemical properties and sensory quality were determined.The response surface method was used to extract the essential oil from the tea by ultrasonic extraction.The extraction process of tea soup was optimized based on the extraction rate of tea polyphenols.The tea soup was purified by refrigerated centrifugal method,and the purification process parameters were optimized by sensory evaluation.On the basis of the above research,a new technology for preparing instant jasmine tea powder was developed.The sensory evaluation,biochemical components and aroma components were compared between instant jasmine tea powder with traditional technology and tea soup after brewing of jasmine tea,so as to provide a basis for popularization and application of the new technology for preparing instant jasmine tea powder.The main research results are as follows:(1)The optimum parameters of saturated water solution method for embedding essential oil were as follows: core wall ratio of 1:4(m L:g),embedding temperature of 60℃,embedding time of 2h,the embedding rate of microcapsules was 88.71±0.79%.The optimum parameters of vacuum freeze-drying method for embedding essential oil were as follows: core wall ratio1:8(m L:g),composite wall material ratio(acacia: β-cyclodextrin)4:3(g:g),solid content 20%,and the embedding rate of microcapsules was 92.06±0.68%.The results show that vacuum freeze drying method is better than saturated water solution method.(2)The optimal distillation time of jasmine tea was 30 min,and the extraction rate of essential oil was 49.50mg/100 g.Aroma identification of the essential oil showed that the components with high content were phenyl-methyl acetate,linalool,phenyl ethanol,phyllyl benzoate,methyl salicylate and methyl aminoanisate,which accounted for 41.78%,18.54%,11.10%,7.51%,7.16% and 6.56% of the total essential oil,respectively.The essential oil of jasmine tea was embedded by vacuum freeze-drying method,and the properties of microcapsules were determined.The water content was 4.08±0.22%,the solubility was94.59±0.42%,the Angle of rerest was 39.01±0.60°,the volume density was 0.62±0.01g/m L and the bulk density was 0.70±0.01g/m L,indicating that the microencapsulated essential oil of jasmine tea was easy to preserve and had good fluidity.The surface of the microcapsule was smooth and there were a few depressions,which were irregular patches without cracks.Fourier transform spectroscopy and thermogravimetric analysis showed that the essential oil of jasmine tea was successfully encapsulated in microcapsules.(3)The optimal extraction parameters were as follows: the ratio of liquid to solid was 40:1,the ultrasonic time was 41 min,and the ultrasonic temperature was 65℃.The extraction rate of tea polyphenols was 24.54±0.29%.(4)The optimum process parameters for refrigerated centrifugal purification of jasmine tea soup are as follows: concentration ratio 4.5,rotation speed 2800 rpm,temperature 10℃,sensory evaluation score of 90.48±0.08 under the preparation conditions.After freezing centrifugation,various substances showed different degrees of sedimentation loss,among which the loss rates of dry matter,tea polyphenols,caffeine,flavonoids,catechin,soluble sugars and amino acids were 20.83%,26.79%,29.77%,22.88%,19.88%,13.06% and 8.88%,respectively.(5)On the basis of the above studies,a new preparation process of instant jasmine tea powder was formed:(1)Preparation of jasmine tea essential oil microcapsules: raw material →water distillation to extract essential oil → essential oil microcapsules;(2)Preparation of tea powder: tea blank after extraction of essential oil → ultrasonic-assisted extraction → vacuum concentration → refrigerated centrifugal purification → spray drying;(3)Mixing: The(1)+(2)is fully mixed to make the new technology instant jasmine tea powder.The instant jasmine tea powder of the new technology,the instant jasmine tea powder of the traditional technology and the tea soup after brewing were respectively evaluated by sensory,and the physicochemical components and aroma components were compared.It was found that the flavor quality of the instant jasmine tea powder of the new technology was superior to that of the instant jasmine tea powder of the traditional technology,and the flavor quality of the tea soup after brewing the original jasmine tea was close to that of the original jasmine tea.It is indicated that the quality of instant jasmine tea powder prepared by this process can be improved.