Effect of Bacillus methylotrophicus on Aging Process and Aroma Precursors of Primary Cured Greenish Tobacco in Luoyang

In order to improve the quality of Luoyang primary cured greenish tobacco and enhance the industrial utilization value of greenish tobacco, four concentration gradients of the bacterial solution of Bacillus methylotrophicus was set including 0%（CK）, 12%（S₁）, 24%（S₂）, and 36%（S₃）, and was sprayed on the top（B2V） and middle（C3V） of Luoyang primary cured greenish tobacco. The effect of Bacillus methylotrophicus on appearance quality and smoking quality of tobacco was analyzed, and the changes in the content of aroma precursors in the tobacco were also determined using gas chromatography and amino acid analyzer. The results showed that spraying of Bacillus methylotrophicus resulted in deepening of color, weakening of greenish color, and increase in uniformity of primary cured greenish tobacco. The content of polyphenols was elevated in the upper and middle parts of the primary cured greenish tobacco affected by Bacillus methylotrophicus, and its spraying 24% concentration was more effective. The content of non-volatile organic acids was elevated by the effect of Bacillus methylotrophicus, and its spraying 36%, and 24% concentration was more effective for the upper and middle tobacco leaves, respectively. The content of free amino acids was reduced, and spraying 24% concentration was the most effective. The optimal concentration of spraying in the storage of raw tobacco is 24%, which can effectively increase the aging speed and improve the quality of tobacco.