Study On The Changes In Composition Of Tobacco During Microbial Fermentation And Its Relationship With Quality

Tobacco is an important and special economic crop in China.Natural fermentation is commonly used in the industry to improve the quality of tobacco,with a long fermentation cycle and difficulty in controlling cost.Microbial fermentation can shorten fermentation cycle and improve tobacco smoking quality at the same time,which is gradually becoming an important processing technology in tobacco industry.However,the existing microbial fermentation technology of tobacco is not mature along with limited application.In this paper,the optimum fermentation technology on tobacco by Lactobacillus plantarum was optimized by screening strain commonly used in the food industry,and regulating the external carbon and nitrogen sources as well as fermentation time.Based on that,the changes in the main chemical components of tobacco during fermentation was investigated.Finally,partial least square regression(PLSR)was used to analyze the correlation between chemical indexes and sensory indexes of fermented tobacco.The research results were listed as follows.The optimum fermentation technology of tobacco was optimized by single factor combined with influence of factor interaction experiment and listed as follows: the addition amount of Lactobacillus plantarum,glucose syrup and soy protein peptide were 0.8 ‰,5 ‰,0.05 ‰,respectively and fermentation time was 8 d.Under this fermentation process,the starch content decreased to the most extent by 44.8%.The sensory quality of tobacco fermented by the three strains was sorted as follows: Lactobacillus plantarum> Aspergillus oryzae> Aspergillus niger.The content of water-soluble total sugar and reducing sugar in tobacco from various regions fermented by Lactobacillus plantarum were higher than that of fermented by other strains.The changes in each chemical composition of tobacco during the process of fermentation by Lactobacillus plantarum were different.During the fermentation time from 0 to 14 th day,the water-soluble total sugar and reducing sugar content of tobacco from each region firstly increased rapidly and then decreased slowly;total nitrogen and protein content decreased rapidly from 0 to 2nd day and then slowly from 2 to 14 th day.There was no obvious change in volatile acid content from 0 to 5th day and then it increased rapidly from 5th to14 th day;volatile alkali content increased slowly from 0 to 14 th day.The total content of free aminoacids decreased from 0 to 8th day,and then remained stable after 8 days.Total number of 65 volatile aroma compounds was detected in the fermentation process,with nitrogen compounds being the largest proportion(51.39?56.61%)and 11 new aroma substances emerged after fermentation.The comprehensive results of PCA analysis,difference analysis and PLSR analysis found that there were significant differences in chemical and sensory indicators of fermented tobacco from 15 production regions(p<0.05),and there was a significant correlation between the two indicators.The aroma content and aftertaste score of fermented tobacco from Lincang region,Yunnan were significantly higher than those from other production regions(p<0.05);the scopletin and petroleum ether extract content of fermented tobacco from Jiangxi production region were significantly higher than those from other production regions(p<0.05);the total alkaloid and total nitrogen content of fermented tobacco from Guizhou production region were significantly higher than those from other production regions(p<0.05).The water-soluble total sugar,threonine and chlorogenic acid of the fermented tobacco from each production region were significantly positively correlated with the aroma amount;nitrogen-nicotine ratio,tyrosine and petroleum ether extracts were significantly positively correlated with irritation;water-soluble total sugar,alanine and chlorogenic acid were significantly positively correlated with aftertaste.