Studies On The Efficient Aroma-increasing Microbial Strains Of Flue-cured Tobacco And Their Effects On The Quality Of Tobacco Leaves

Tobacco is a cash crop used for its leaves, Quality of flue-cured tobacco leaves is more important. Large amount of low-tar cigarette appears consecutively with the Smoking and Health problem raised, Concentration of aroma of cigarette is reduced after lowering tar content of cigarette. In order to increase concentration of aroma and to improve the quality of Flue-cured tobacco leaves, researches were conducted as follows in this paper. Firstly, efficient microbial strains were isolated from cured tobacco leaves, tea and dried bamboo shoots. Secondly, the influences of efficient bacterial strains on quality of flue-cured tobacco leaves were studied. Thirdly, the influences of efficient fungi strains on quality of cured tobacco leaves and its mechanism were studied. The results are as follows.Firstly,96 bacterial strains and 121 fungi strains are isolated from tobacco leaves, tea and dried bamboo shoots.Secondly, Compared with the control, the main chemical component of tobacco leaves which was inoculated with 39 Bacterial strains has shown a significant change. The content of organic acid of cured tobacco leaves can be increased by 23 bacterial strains and especially more higher by YX12, YX21, YX11, YX47, YX59, YX33, YX3, YX44, YX37 and YX46. The content of petroleum ether extract of cured tobacco leaves can be increased by 17 bacterial strains and especially more higher by YX21, YX37, YX11, YX46, YX59, YX3, YX12, YX33 and YX44. The sensory testing result of cured tobacco leaves can be improved by 20 bacterial strains and especial more higher by YX33, YX12, YX59, YX15, YX47, YX21, YX37, YX11, YX3.39 bacterial strains, which the main chemical components of those are different with the control, are divided into four groups based on a cluster analysis. Group Four (YX3, YX15, YX12, YX59, YX21, YX37, YX33, YX44, YX47, YX11 and YX46) can improve the sensory quality of cued tobacco leaves. The scores of the Group Four are higher than the control (64.83) and range from 67.5 to 70.8. Identification results of microbial strains show that YX37 belongs to Bacillus; YX59 belongs to Enterobacter-Enterobacter hormaechei.Compared with the control, the main chemical component of tobacco leaves which was inoculated with 34 Fungus strain has shown a significant change. The content of organic acid of cured tobacco leaves can be increased by 27 fungi strains and especially more higher by CZ11, SZ8, CZ4, SZ14, CZ7, YZ2, CZ16, CZ43 and CZ60.The content of petroleum ether extract of cured tobacco leaves can be increased by 33 fungi strains and especially more higher by SZ14, CZ26, CZ16, CZ11, CZ7, SZ28, CZ3, YZ2, CZ50. The sensory testing result of cured tobacco leaves can be improved by 29 fungi strains and especial more higher by YZ2, CZ11, CZ4, CZ7, SZ14, CZ16, SZ8, CZ60, CZ43.34 fungi strains, which the main chemical components of those are different with the control, are divided into four groups based on a cluster analysis. Group One (YZ2, SZ8, CZ4, CZ43, CZ11, SZ14, CZ7, CZ16) can improve the sensory quality of cued tobacco leaves. The scores of the Group One are higher than the control (58.41) and range from 72.04 to 73.29. Identification results of microbial strains show that YZ2 belongs to Trichoderma-Trichoderma longibrachiatum. SZ14 belong to AspergiLLus.Thirdly, the results of the orthogonal design experiment shows that bacterial strains and its concentration have extremely significant influence on chemical components, leaf structure and sensory testing results of cured middle and upper leaves. Spraying times of bacterial strains have significant influence on chemical components and sensory testing results of middle and upper leaves but have no influence on leaf structure indices, spraying three times of YX37 and the concentration being 3×109 CUF·L-1 is the best treatment which can increase the density of glandular hairs and the content of aroma precursor, make leaf structure loose and improve sensory testing results of cured tobacco leaves.Fourthly, the results of the orthogonal design experiment shows that different fungi strains and its concentration have significant or extremely significant influence on the content of aroma precursor and sensory testing results of cured leaves. The pH and ferment times of different fungi strains have significant influence on some contents of the aroma precursor and have no influence on sensory testing of cured tobacco leaves. The ferment temperature has significant influence on some contents of the aroma precursor and sensory testing of cured tobacco leaves. YZ2 fungus strain, Concentration of 6×109CUF/L(B3), Ferment time of 12d and Ferment temperature of 28℃could increase the contents of aroma precursor and improve Sensory testing of tobacco leaves.The treatment A1B4C4D4E4 (6×109 CUF·L-1 fungi strain YZ2, the pH being adjusted to 5.5, fermented for 12 days at 32℃); the treatment A1B3C3D3E3 (6×109 CUF·L-1 fungi strain YZ2, the pH being adjusted to 5, fermented for 9 days at 30℃) and the treatment A1B2C2D2E2 (6×109 CUF·L-1 fungi strain YZ2, the pH being adjusted to 4.5, fermented 6 days at 28℃) are all the best choice which can improve the contents of the aroma precursor and the sensory testing quality of cured tobacco leaves.The results of aroma substances of flue-cured tobacco leaves, which are analyzed by using the principal component method, shows that ketone, propylene-3-methyl-pyrazine, indole and vinyl polymer were the principal components. Alkanes was the second main components. Aldehyde and acetylfuran were the third main components. T-tests of aroma substances of Flue-cured tobacco leaves showed no significant difference between treatments 2,3,4,7,8 and treatment 16; between treatments 2,3,4,8 and treatment 10; between treatments 2,4 and treatment 7; between treatments 2 and treatment.5 and between treatments 2 and treatment 4; significant difference between other treatments; But there is no positive correlation between the contents of aroma substances and the quality of the sensory testing of cured tobacco leaves.Fifthly, after inoculated by the four fungi strains (YZ2, CZ11, CZ16 and SZ14), the activities of amylase, protease, cellulase, polyphenol oxidase and peroxidase of curd tobacco leaves increases first and then decreases along with the ferment time. after inoculated by the four fungi strains (YZ2, CZ11, CZ16 and SZ14), the activities of amylase, protease, cellulase, polyphenol oxidase and peroxidase of curd tobacco leaves are higher than control, Inoculated with fungi strains CZ11 or CZ16, the activities of amylase, polyphenol oxidase and peroxidase of cured tobacco leaves are relatively high. And inoculated with fungus strain YZ2, the protease activity of curd tobacco leaves is relatively high. Then inoculated with fungus strain SZ14, the cellulase activity of curd tobacco leaves is relatively high.