Monitoring Black Tea Fermentation Using A Colorimetric Sensor Array-based Artificial Olfaction System

Fermentation is the critical process of black tea production and plays an important role on the quality formation of black tea.In the process of black tea traditional fermentation,skilled works determine the degreee of fermentation through color,aroma and taste of black tea based on subjective judgement.In recent years,with the development of technology,some new methods such as spectroscopy detection technology,computer vision technology,electronic nose and so on are gradually applied to the proper identification of black tea fermentation,but these detection techniques also exist some disadvantages such as baseline drift,environmental interference and big noise.This paper proposed a colorimetric sensor array-based artificial olfaction system to monitor black tea fermentation and explored the feasibility of this technology in the process of black tea processing.1.Based on related literature,this paper completed the screening of chemical dyes and plates.Herein,a colorimetric sensor array was achieved,which was fabricated by printing 16 chemical dyes,including metalloporphyrins on a Silica gel thin-layer chromatography plate.The study designed to produce a sense of olfactory visualization data acquisition device and the device is convenient and quick.This paper developed the analysis software to improve the efficiency of analysis.The experments were used to optimize the detective techonology.And the result showed that the optimal rection time of sensor and fermention tea leaves is 8 minutes,and the effect of temperature and humidity of envirment is small.2.According to the results of previous experiments,the self-made olfactory visualization detection system was used to determine the degree of fermentation.The olfactory visualization and the sensory evaluation data were collected.Discrimination model was established by fisher discriminatory analysis and adaptive boosting algorithm based on BP-ANN(BP-Adaboost).Results showed that the discrimination rate and discrimination rate of cross-validation reached 100% and 90.74% respectively.BP-Adaboost model showed that the correlation coefficient of calibration set(Rc)and prediction set(Rp)were 0.9578 and 0.9132 respectively.This work demonstrates that it is feasible to distinguish the degree of black tea fermentation using a colorimetric sensor array-based artificial olfaction system.3.Experment were carried out to detect volatile substances of black tea fermentation process and the result showed the trend of type,number and content of volatile substances changes.As the extension of time during the fermentation procedure,the contents of alcohols and esters decreased,the contents of aldehydes increased first and then decreased and reached the highest value in about 3 hours.The prediction models of total volatile matter were established during the fermentation process of black tea,and most of the volatile substances were correlated with olfactory visualization data.The prediction models for the total amount of alcohols,aldehydes and esters in the fermentation process were established.Data analysis showed that the correlation coefficient of calibration set(Rc)were all more than 0.85 and the correlation coefficient of prediction set(Rp)were all more than 0.65.The results showed that the sensor was sensitive to total volatile matter.The prediction models of Benzaldehyde,Benzyl Alcohol,Linalool,Linalool oxide,Methyl Salicylate,Geraniol contents were estabished.The results showed that the correlation between olfactory visualization data and benzaldehyde,benzyl alcohol and geraniol changes is more good,and the predictive set correlation coefficient is above 0.8,so the effective prediction of these substance can be achieved.This experiment confirmed that the olfactory visualization technique can be used to determine the degree of fermentation of black tea.