Quality Change And Shelf Life Prediction Of Matcha During Processing And Storage Period

Matcha is a micronized product that has been ultrafine grinding after being shaded by steam fixation(or hot air fixation).In this paper,the physicochemical characteristics of matcha in the processing process were studied,and the relationship between physicochemical characteristics of different particle sizes was analyzed.Three different particle sizes of matcha were selected for low-temperature storage,and the changes of various quality indicators during storage were analyzed.Setting different temperature conditions,the quality changes of matcha during storage were analyzed,and the predictive model of shelf life was constructed.The detailed research and results are as follows:(1)Taking the physicochemical characteristics as indicators,the tencha was superfine grinding by a production type ball mill to obtain matcha with medium particle size of 117.094,60.176,40.041,30.646,25.282,21.090,19.199 and 14.209 ?m,and to explore the physicochemical characteristics of matcha at different particle sizes.The results showed that with the pulverization time prolonges,the particle size of the powder gradually decreases and the degree of cell breakage increases remarkably.However,the functional group structure of the main component of the tea powder does not change;when the particle size is refined to a certain extent,the specific surface area and surface energy increase,the particles are in an unstable energy state,and prone to adhesion and agglomeration;the bulk density of the powder reduces,which is related to the increase of the porosity of the powder;due to the increased specific surface area of the tea sample,the internal substances of the powder exposes,so that the water content reduces,the total water content reduces;The brightness of tea powder gradually increases,and the greenness increases;with the pulverization time prolonges,the content of tea polyphenols,free amino acids and other substances increased first and then decreased,while the contents of ascorbic acid and EGCG tend to reduce.The above results show that the superfine grinding process has a significant impact on the physicochemical characteristics of matcha.(2)In order to understand the storage characteristics of different sizes of matcha under low temperature conditions,three different particle size samples(1700 ?m,17.150 ?m,12.927 ?m)were selected as the research object.The sample was stored at 4? and the quality index is determined at intervals.The results showed that the smaller particle size,the greater degree of color change of the sample;the overall moisture of the sample showed a downward trend,and the original tea decreased slowly;tea polyphenols,chlorophyll and ascorbic acid all showed a downward trend.With the prolongation of storage time,the smaller the particle size,the faster the quality content drops.(3)Matcha as experimental material,the quality changes of matcha during storage under four temperature conditions(-18?,4?,25?,37?)were analyzed,and the predictive model of shelf life was constructed.The results showed that the chlorophyll,color,tea polyphenols,ascorbic acid and sensory evaluation of matcha showed a downward trend at each storage temperature,while moisture content showed an upward trend.Person correlation analysis showed that moisture content and chlorophyll content of matcha quality was the highest correlation with sensory evaluation.Based on the Arrhenius equation,the shelf life prediction model of matcha was established.The activation energy Ea in the moisture content and chlorophyll prediction model was 10269.77 KJ·mol-1 and 7140.86 KJ mol-1,respectively.The pre-exponential factor K0 was 0.6594 and 0.2721,respectively.The experimental results show that the theoretical shelf life is consistent with the actual shelf life,and the shelf life of matcha can be predicted based on moisture content and chlorophyll.