Intelligent control for quality improvement in green tea fixation assisted with aroma detection

An intelligent control system is designed in green tea fixation, which can automatically and continuously adjust the fixation parameters for quality improvement. Aroma is detected with PEN-3 electronic nose, and signals are sent to the computer. With the aroma signals, the fixation process is separated into two stages: in the first stage, the key purpose is enzymatic reaction, which can be suppressed with high temperature; it is the oxidation reaction which should be concentrated on in the second stage, and a middle temperature is a good choice. With the designed fuzzy logic algorithm, the pot temperature is kept at a high level at the beginning, and the enzymatic reaction can be successfully reduced. In the second stage, the temperature is kept at a middle value to decrease oxidation. With the designed intelligent control, the green tea product quality is improved for aroma, taste, appearance, liquor color, and residues.