Abstract: In order to study the effect of ozone on the quality of over aged tobacco raw materials and solve the problem of over aged tobacco mold, two sets of different ozone concentration levels （0、50、100、150 μmol/mol; 0、100、200、300 μmol/mol） and three ozone treatment times （30、60、90 days） were set up to study the effects of ozone on the anti mold effect, color and quality of aged tobacco leaves for 3 and 7 years. The results showed that treating tobacco leaves with 200 μmol/mol ozone for 60 days could kill mold and remove most of the moldy odor. After 90 days of treating tobacco leaves with 50~150 μmol/mol ozone, the color transition to brownish black was significantly inhibited. For tobacco leaves that had been aged for 3 years, ozone treatment would have a significant negative effect, resulting in poor quality. For tobacco leaves that had been aged for 7 years, ozone treatment would have a significant positive effect, and 100 μmol/mol ozone had the best effect on improving the quality of tobacco leaves. Therefore, ozone could improve the quality of excessively aged tobacco raw materials, increase their utilization value, and effectively eliminate tobacco leaf mold, solving the problem of tobacco raw material mold. However, for tobacco leaves that had just passed the optimal aging period, ozone treatment should not be used.

Key words: ozone, mouldy tobacco leaves, over aged tobacco leaves, conventional chemical composition, sensory quality