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On the basis of 213 flue-cured tobacco samples from 5 main tobacco-growing areas of China, including 47 upper leaves, 141 middle leaves and 25 lower leaves from tobacco region in southwest, southern China, central south China, Huang-huai and northern China, geographical distribution of styles about flue-cured tobacco was analyzed. The differences of chemical composition, aroma substance and sensory quality in different aroma types were compared. The relationships of aroma constant and sensory quality were studied. In the end, discriminatory analysis of aroma types was applied using aroma substance. The principal research conclusions were as follows:1. The regional distribution of aroma types about flue-cured tobacco of China was analyzed. There were evidently distinctive characteristics in regional distribution of aroma types. Fen-flavor and middle flavor were expressed in the south, particularly in Yunnan province showing typical fen-flavor, in Guizhou province and Chongqing city with middle flavor. The north was mainly enriched and middle flavor, Huang-huai tobacco regions belonging to representative enriched flavor and the north standing for middle flavor.2. Difference analysis on common chemical component, polyphenols, organic acid, aroma component, sensory quality in different aroma types was conducted. The results showed that carbohydrate, ether extract, protein of 9 chemical components had significant difference in different aroma types. The content of total sugar and reducing sugar showed fen-flavor> middle flavor> enriched flavor, but ether extract and protein showed enriched flavor > middle flavor> fen-flavor. The content of chlorine and total plant alkaloid in enriched flavor were significantly higher than that in fen-flavor, with minimum potassium content (1.97%). There was no significant difference of total nitrogen and pH value in three aroma types. Fen-flavor flue-cured tobacco had maximum total polyphenols content and enriched flavor showed lowest. Chlorogenic acid had no significant difference in three aroma types. The difference of scopoletin and rutin reached to significant level, which the content of scopoletin showed enriched flavor > middle flavor> fen-flavor, but rutin content showed fen-flavor> middle flavor> enriched flavor. The diversity in organic acid was different. The content of malonic acid, succinic acid, malic acid in enriched flavor were significantly higher than that in fen-flavor, but enriched flavor had significantly lower content of hexadecanoic acid, oleic acid, stearic acid than fen-flavor. There was no significant difference of citric acid, lauric acid, myristic acid in three aroma types. Caprylic acid, pelargonic acid, total acidic aroma components showed no significant difference in three aroma types. The content of valeric acid, caproic acid, heptylic acid in enriched flavor were significantly higher than that in fen-flavor, but enriched flavor had significantly lower content of capric acid, isovaleric acid than fen-flavor. Total content of neutral aroma constituents showed middle flavor> fen-flavor> enriched flavor, with higher content of hyacinthin, 6-methyl-5-heptene-2-ketone, geranyl acetone, farnsylacetonein in enriched flavor tobacco leaves.3. Correlation analysis was applied to study the relationships between sensory quality and aroma constituent in different flue-cured tobacco with aroma types. The relativities between smoke characteristics and aroma constituent of enriched flavor flue-cured tobacco, taste and aroma constituent of fen-flavor flue-cured tobacco were superior. But aroma constituent of middle flavor was well related with smoke characteristics and taste. For three aroma types, the correlation between neutral aroma constituents and sensory quality was better than that between acidic aroma components and sensory quality.4. The relationships between routine chemical composition, polyphenols, organic acid, aroma constituent and sensory quality were researched by superior analysis. Total sugar, reducing sugar, hexadecanoic acid, stearic acid were the quasi-optimal factors of affecting sensory quality of enriched flavor flue-cured tobacco, and the quasi-optimal factors which influenced sensory quality of fen-flavor were total sugar, potassium, succinic acid, rutin. The quasi-optimal factors which affected middle flavor were total plant alkaloid, potassium, hexadecanoic acid, scopoletin. Linalool, neoplytadiene, damascenone, solanon, butyric acid, hyacinthin and dihydroactinidiolide had a great influence upon enriched flavor tobacco leaves. The aroma constituent such as caprylic acid, 2-acetylfuran, indole and furfuryl alcohol displayed larger effect on fen-flavor tobacco leaves. Hyacinthin, geranyl acetone,β-ionone,β-Damasencone showed great impact on middle flavor tobacco leaves.5. The mathematical model for identifying aroma type of flue-cured tobacco was established through stepwise discriminant analysis including aroma substance as variable. The results indicated that seven aroma constituents were included in the discriminant function, and variance analysis revealed that differences in aroma types were significant. The discriminant functions were re-discriminated by using the methods of self and mutual test with a discrimination accuracy being 76.6% and 75.65% respectively. The discrimination accuracy for new samples was up to 83.3% and the discriminant functions were verified well in discrimination results.
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