Study On Process Control Of Green Tea Far Infrared Processing Based On Aroma

In the green tea processing process,fixation and drying are two core processes that affect the quality of green tea.Green tea is fixed to blunt the activity of polyphenol oxidase enzymes to avoid redness and browning,while retaining the components contained in green tea to form the unique flavor of green tea.After fixing,the green tea is dried to further reduce the moisture content,prevent mold and mildew,and facilitate storage,while using high temperature to enhance the aroma quality of green tea.Traditional green tea processing mostly relies on the experience of tea masters,and the machine processing process also requires manual operation,which greatly increases the time and labor cost and is not conducive to industrial green tea production.In this project,the PEN3 electronic nose was employed to timely monitor the odor information of green tea during green tea fixing and drying process,the change law of electronic nose response value was deeply analyzed combined with GC-MS technology,and then the correlation with green tea quality was established,and finally,a fuzzy feedback control strategy was developed to control the green tea processing process.The specific research contents were as follows:(1)An experimental system of far-infrared processing of green tea based on odor online monitoring was built.The far-infrared radiation temperature control unit,the odor real-time monitoring unit,the weight detection unit,and the PC control unit were completed,and the farinfrared radiation temperature control strategy based on Lab VIEW was designed.Through testing verification,the error range of temperature control system was maintained ranged from-3 ℃ to 3 ℃,and the system had good stability.(2)The change law of quality parameters during green tea fixing process with constant temperature was explored.First,the green tea fixing experiments at 120 ℃,130 ℃,140 ℃,150 ℃ and 160 ℃ were designed,the characteristic sensors W5 S,W1S and W2 W in the fixing stage were screened out.Then,the change law of electronic nose response value was analyzed combined with GC-MS technology.Finally,polyphenol oxidase activity,tea polyphenols,amino acids and other quality parameters during the fixing process were determined,and the correlation between the change of response values of electronic nose sensors and green tea quality parameters was established.The analysis found that the W2 W sensor could be used to monitor the degree of aroma emission,the W1 S sensor could be used to monitor the degree of oxidation reaction occurrence,and the W5 S sensor could be used to monitor the degree of scorching occurrence.(3)The change law of quality parameters during green tea drying process with constant temperature was investigated.First,green tea drying experiments at 160 ℃,170 ℃,180 ℃,190 ℃ and 200 ℃ were designed,the characteristic sensors W5 S,W1W and W2 W in the drying stage were screened out.Then,the change law of electronic nose response value was analyzed combined with GC-MS technology.Finally,tea polyphenols and amino acids and other quality parameters during the drying process were determined,and the correlation between the change of response value of electronic nose sensor and green tea quality parameters was studied.The results showed that the W5 S sensor could be used to monitor the occurrence of scorch during the drying process of green tea,and also to monitor the changes of water content,the W1 W sensor could be used to detect the degree of chestnut flavor emitted during the drying process of green tea,the W2 W sensor could be used to monitor the aroma quality during the drying process.(4)A fuzzy control strategy was designed to optimize control of green tea processing quality.According to the difference of the response values of the characteristic sensors in the fixing and drying process,the input quantity was selected reasonably,and the fuzzy inference rules were formulated by using Lab VIEW fuzzy controller,and after fuzzy inference and defuzzification,the appropriate temperature adjustment quantity was output to achieve the purpose of optimizing the processing quality of green tea.