| Summer-autumn tea contains a huge amount of tea polyphenols but the demand and price are very low due to its poor taste and color,which affects the enthusiasm of tea farmers in production that incurs a great loss of summer and autumn tea resources.At present,various functional instant tea products have been developed using Xiaqiu tea namely a summer-autumn tea,which based on the realization of high-value utilization of low-value Xiaqiu tea is an important way to upgrading the tea industry.The control of process parameters of the traditional oxidative fermentation process of summer-autumn tea extracts is highly dependent on working experience causing poor product quality.This thesis focus on the improvement and development of oxidative fermentation technology of summer-autumn tea and related systems based on the research of oxidative fermentation technology of summer-autumn tea combined with non-destructive detection technology and fuzzy control theory.The main research contents and conclusions are as follows:1.Study on the optimization of oxidative fermentation parameters of summer-autumn tea.Aiming at the problem of unclear fermentation conditions of summer-autumn tea,orthogonal experiment and response surface experiment methods were used to carry out the experiment.A three-factor three-level quadratic orthogonal experiment was designed for the measurements of total sugar and tea polyphenol utilization rate after the fermentation as response indicators under the control of fermentation conditions such as temperature,pH,and inoculation amount.The results showed that the coefficient of the quadratic polynomial model equation of the tea polyphenol consumption rate was 0.92;the coefficient of the quadratic polynomial model of the total sugar consumption was 0.8564,indicated that the model is significant.The study showed that the experiment clearly defines the fermentation parameters,which lays the foundation for establishing a control model of the oxidative fermentation parameters of summer-autumn tea.2.Research on online monitoring technology of oxidative fermentation process of summer-autumn tea.Aiming to minimize the problem of online monitoring of state parameters such as tea polyphenols,total sugars,and color values,the visible/near-infrared spectroscopy technology was used to develop a rapid monitoring technology for the oxidation and fermentation process of summer-autumn tea.The visible/near-infrared spectrum was processed by SNV and 2-order 9-point SG smooth superposition.The competitive adaptive weighted sampling algorithm(CARS)was used to screen the spectral wavelength,also a quantitative model of CARS-PLS was established.The results showed that the correlation coefficient of the spectral prediction model of tea polyphenols was 0.9065 and the RMSE was 0.0867 mg/mL.The correlation coefficient of the spectral prediction model for total sugar was 0.9078,and the RMSE was 0.3151 mg/mL.The visible bands in the spectrum were used to calculate the color value of the fermentation broth by the method of equal wavelength interval,and the color space of L*a*b* was adopted.The results showed that the MRE of the predicted color value was 1.15%.Studies have shown that it is feasible to detect the contents of tea polyphenols and total sugars and color values of the summer-autumn tea broth by using visible/near-infrared spectroscopy.The developed spectral prediction model can accurately predict the state of the summer-autumn tea broth.3.Research on the fuzzy control method of oxidative fermentation process of summer-autumn tea.Aiming at the problem of strong subjectivity and poor stability of working experienced fermentation parameters,a fuzzy control method was used to study the oxidative fermentation of summer-autumn tea.Based on Mamdani fuzzy reasoning method,a fuzzy control system with three input parameters and four output parameters was constructed.Simulation results showed that the fuzzy control system can accurately control fermentation parameters.Overall results suggested that fuzzy control can be used to control the oxidative fermentation process of summer-autumn tea,and developed a scientific control method for the oxidative fermentation control system of summer-autumn tea.4.Research on the development of a monitoring system for oxidative fermentation process of summer-autumn tea.In order to online monitor the optimum oxidative fermentation levels of summer-autumn tea,a software and hardware joint development method was used to ease the monitoring of fermentation levels.The hardware system includes a fermentation tank,visible/near-infrared spectrometer,light source,lower machine control cabinet,etc.The software system runs on a Windows system,and its function is to collect and process visible/near-infrared spectral data,execute fuzzy control programs and return control parameters.The results showed that the system can accurately predict tea polyphenols,total sugar content,and color(L*a*b*)values during fermentation.The MAE of tea polyphenol prediction was 0.134 mg/mL,and the MRE was 6.24%,and the maximum coefficient of variation of the predicted value was 4.23%;the MAE of the total sugar content prediction was 0.176 mg/mL,the MRE was 6.68%,and the maximum coefficient of variation of the predicted value was 2.55%;the MAE of the color value prediction was 0.257,the MRE was 1.15%;the MRE of the fermentation control parameters was less than 5%.Studies have shown that the fermentation system of this study can efficiently ferment summer-autumn tea.This paper mainly studied the optimal parameters of the oxidative fermentation process of summer-autumn tea,and the nondestructive detection method of oxidative fermentation of summer-autumn tea,and combines fuzzy control theory to realize the intelligent control of oxidative fermentation of summer-autumn tea,and finally developed a set of oxidative fermentation control of summer-autumn tea system.The research conclusion showed that the research and development of the Xiaqiu tea oxidative fermentation control system can effectively improve the automation level of the summer-autumn tea oxidative fermentation process,which is in line with the research expectations. |
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