Abstract:
To address over-reliance on manual experience and the lack of quantitative indexes for regulating the piled fermentation of domestic cigar tobacco leaves, the temporal change patterns of the pile core temperature was analyzed. A total of 45 domestic cigar tobacco piles were studied, and their core temperature sequences were monitored. Dynamic time warping algorithm (DTW) was used to measure the similarity between the different temperature sequences, followed by k-means++ algorithm for temperature time series clustering analysis. By analyzing the dynamic characteristics of the various temperature change patterns, a multi-factor decision-making framework integrating temperature change patterns, sliding 24-hour temperature differences, temperature thresholds and fermentation time was constructed. The results showed that: 1) During the piled fermentation process, the core temperature exhibited five different change patterns including stable low temperature, steady warming, rapid warming, stable high temperature, and medium temperature fluctuation. 2) For the stable low temperature type, it was recommended to turn over the pile when the fermentation time exceeded 120 hours and the core temperature was below 30 ℃. For the steady warming type, it was recommended to turn over the pile when the fermentation time exceeded 168 hours and the core temperature was below 35 ℃. For rapid warming or stable high temperature type, when the core temperature exceeded 45 ℃ or the sliding 24-hour temperature differences was ≤0 ℃, a pile turnover warning could be triggered, and for the medium temperature fluctuation type, when the cumulative fermentation time of the entire cycle exceeded 30 days, the current stage fermentation time exceeded 168 hours, and the sliding 24-hour temperature difference was ≤0 ℃, it could be determined that the fermentation was over and the product could be discharged. 3) The use of decision framework method to assist in pile turnover enabled early prediction of the fermentation endpoint, reduced the constant temperature or cooling time at the end of each fermentation stage, and improved fermentation efficiency. This study provides a quantitative decision-making strategy for cigar tobacco piling, pile turnover, and pile discharge, and offers technical support for the digital control and standardized production of cigar tobacco fermentation.