Research On Green Tea Pot-type Fixating Process Control Based On Odor And Visual Inspection

When using pot-type fixating equipment,the tea farmer stirs the tea leaves in the pot and adjusts the pot temperature in time according to the difference in the smell and color of the tea to change the heat of the tea.Because of the advantages of artificial sensory feedback control,this method of fixating is mainly used to process precious tea.However,due to the influence of subjective factors and environmental factors,the uniformity of this fixating method is poor,and the pot temperature is manually controlled,which is labor intensive.Therefore,this paper uses fresh green tea leaves as experimental materials,and uses PEN3 electronic nose and visual online detection technology to replace human sense of smell and vision.The odor and color of green tea during the process of fixating at different constant pot temperatures are measured,and their changes and changes are measured.The mechanism is studied,and at the same time,the relationship between it and quality is established,and three fuzzy control fixating schemes based on odor online detection,based on visual online detection,and based on odor and visual online detection are designed to be completed.In this paper,a green tea pot-type fixating experiment system based on odor and visual detection is built.The system contains 5 parts,namely,the odor online detection part,the visual online detection part,the heating and air cooling part,the quenching pot part,and the PC control part.The system can realize online detection of odor and vision and online detection and control of pot temperature.The precision of pot temperature control is±4°C and the control effect is good.During the fixating process,the system automatically records online detection and control data,such as pot temperature,leaf temperature,PEN3 electronic nose sensor response value and color data.In addition,these data are automatically saved in the computer.This paper firstly studies the odor generation mechanism of green tea during enzymatic oxidation,non-enzymatic oxidation,burnt and aroma emission and the response value of the PEN3 electronic nose sensor.It is concluded that 2 sensors is the burnt representative sensor,6sensor is the oxidation reaction representative sensor and 9 sensor is the aroma representative sensor.Then record the sensor response values and quality parameters of 2,6 and 9 in the process of fixating at different constant pot temperatures（160°C,170°C,180°C,190°C,200°C）,and study the effect of pot temperature on odor and quality.It is found that the pot temperature is too high or too low,which is not conducive to the preservation of the smell and quality of green tea.On this basis,the relationship between sensors 2,6 and 9 and quality parameters are analyzed and a fuzzy control algorithm based on online odor detection is designed.The pot temperature is adjusted online according to the changes in the response values of sensors 2,6 and 9,and it is found that the quality of green tea has been improved.Especially the chemical quality is better.Use visual online detection technology to detect the green tea color at different constant pot temperatures（160°C,170°C,180°C,190°C,200°C）during the fixating process.Record the R,G,B components and the measured quality parameters,studied the influence of pot temperature on the color and quality of green tea,and found that when the pot temperature is too high or too low,the color and quality of green tea are both poor.On this basis,the relationship between green tea color and quality parameters is analyzed,and a fuzzy control algorithm based on visual online detection is designed.The pot temperature is adjusted online according to the change of green tea color,and it is found that the quality of green tea has been improved,especially the sensory quality is better.Use PEN3 electronic nose and visual online detection technology to detect the green tea smell and color in different constant pot temperatures（160°C,170°C,180°C,190°C,200°C）and compare them online.Analyzing the feasibility of PEN3 electronic nose and visual online detection technology in different time periods,it is found that the use of R component as the basis for dividing the early stage and the middle and late stages is better than 6 sensors,and according to the changing law of|d（G-R）/dt|,the pot temperature is adjusted to passivate the oxidase activity,and the ability to prevent scorching is better than that of the 2 and 6 sensors.This is because the odor emission requires a process.The use of R and|d（GR）/dt|can achieve early prediction,but the PEN3 electronic nose can detect the aroma of green tea,so we learn from each other’s strengths,design a fuzzy control algorithm based on odor and visual online detection,and find that the chemical quality and sensory quality of green tea have been improved.It was found that the enzyme activity of green tea after fixating was 3.18 U·m L^-1,tea polyphenols was 16.88%,amino acids were 2.45%,chlorophyll was 9.16 mg/g,phenol-ammonia ratio was 6.89,sensory product score was 94.1,and the chemical and sensory qualities of green tea were improved.By comparison,the green tea with fuzzy control based on odor and visual online detection is better than the green tea with fuzzy control based on odor online detection and visual online detection.