Abstract:

The study aims to investigate the difference of the dynamic changes of protease activity and protein content of flue-cured tobacco between the ‘two stews and one stop’ curing and the conventional curing process. The results showed that protease activities presented a ‘double-peak curve’ of up-down-up-down in both the two curing processes, and the first peak occurred in the yellowing period with higher enzyme activity and the second peak occurred in the color fixing period. The protein content showed a downward trend, rapidly declined in the yellowing period, slowly declined in the fixation period, and had little change in the dry gluten period. The yellowing period was the main degradation period of protein, and the degradation range was above 80%. For the two curing methods, the enzyme activities of the two peaks were 208.5 and 199.26 U/mg respectively in ‘two stews and one stop’ curing process, which were 19.46 and 30.63 U/mg higher than those in the control, and the average enzyme activity in the peak interval was higher, the duration was longer, and the peak appeared later than those of the control. The degradation range of protein was greater in ‘two stews and one stop’ curing, and the degradation range during the yellowing period accounted for 89.3% of the total degradation range, 8.5 percentages more than that in the control, and the protein content of flue-cured tobacco was lower. The research results indicates that the activity and duration of tobacco leaf protease can be improved by ‘two stews and one stop’ curing method, which is more conducive to protein degradation and could reduce the protein content of the flue-cured tobacco leaf.

Key words: flue-cured tobacco, flue-curing mode, protein, protease, dynamic change