Comprehensive Evaluation Of Black Tea Fermentation Based On Digital Technology

Fermentation is the most critical step in black tea processing.Traditionally,the evaluation of the fermentation degree of black tea relies on the sensory evaluation analysis of experienced tea masters to observe the color and smell the aroma,and subjectively judge the degree of fermentation of black tea by virtue of years of production experience,which is easily influenced by the environment and state of mind and has poor accuracy,and easily causes under or over fermentation of black tea,resulting in large product variability and inability to standardize.Therefore,there is an urgent need for a scientific,fast and accurate method to determine the degree of fermentation of black tea.In this study,computer vision(CVS)and near-infrared spectroscopy(NIRS)were used to comprehensively evaluate the fermentation process,so as to scientifically and quantitatively discern the degree of fermentation of black tea.The main findings are as follows: summarized into 3 points.(1)To find the intrinsic link between the chemical change process of black tea centered on the oxidation of polyphenolic compounds and sensors,three different algorithms(LDA linear discriminant analysis,SVM support vector machine,and K-neighborhood)were compared for modeling effects to obtain the optimal model performance for NIRS and CVS of the degree of fermentation of black tea.In addition,two mid-level data fusion approaches were used to combine spectral and image information.The results show that the SVM data fusion model based on PCA processing has the best performance and the fermentation degree discrimination rate can reach 100%.(2)Based on the clustering analysis of fermented catechins and tea fusions color of black tea,combined with sensory evaluation,black tea of different fermentation periods were grouped.Develop a portable NIR spectrometer(micro-NIRS)that can be used in large-scale production and carry an inexpensive imaging system by made-lab,the fermentation degree of black tea discrimination rate was 75.67%,81.08%,respectively.(3)The fusion analysis of the data extracted from the micro-NIRS and the inexpensive imaging instrument established a fermentation degree model with a discrimination rate of up to 91.89%.And the intrinsic connection between color and taste and sensors during the fermentation of black tea was explored.