Abstract:

In order to clarify the baking characteristics of the US-introduced tobacco variety ‘NC297’, the traits of color characterization, yellowing and browning, water loss, chlorophyll degradation, and polyphenol oxidase activity of different parts of the tobacco leaves in the dark-box test were investigated by using the intensive baking room and dark-box test method with ‘NC297’ as the material. The results showed that: (1) in the dark-box test, the yellowing degree of the middle and lower leaves was close to 100% at 96 h, while the upper leaves were not completely yellowed until more than 120 h, indicating that the baking ease of the middle and lower leaves of ‘NC297’ was moderate, but the baking ease of the upper leaves was poor. (2) During the baking process, the polyphenol oxidase activity of the upper fresh tobacco leaves of ‘NC297’ was 0.46 ∆OD_{398 nm}/(g·min), significantly higher than that of the middle and lower leaves of ‘NC297’ which was 0.22 ∆OD_{398 nm}/(g·min), indicating that the middle and lower leaves of ‘NC297’ were more resistant to baking, and the upper leaves were moderately resistant to baking. However, the browning degree of the lower leaves was close to 30% at 144 h, which indicated that the browning degree of the lower leaves among different parts of the tobacco was relatively poor. (3) In terms of chemical composition, with the increase of baking time, total sugar, reducing sugar and total amino acid content gradually increased, while total nitrogen, protein and starch content gradually decreased. To summarize, ‘NC297’ has medium baking ease in the middle and lower leaves, poor baking ease in the upper leaves, the order of baking resistance is middle leaves> upper leaves> lower leaves, and the chemical compositions of the flue-cured leaves are more coordinated, and the quality is significantly improved.

Key words: flue-cured tobacco, ‘NC297’, curing characteristics, dark-box test, water loss characteristics, chlorophyll degradation, polyphenol oxidase activity