Effects of Enzymatic Browning and Leaf Browning Inhibitors on Tobacco

Abstract

The maturity of fresh tobacco leaves affects the browning of leaves to differing degrees during the curing process, thus affecting the quality of cured tobacco leaves. In this study, tobacco leaves of increasing maturity (M1–M4) were selected. Dark-box experiments were performed to investigate the roasting characteristics and relationship between tobacco leaf maturity and browning and to determine their polyphenol oxidase (PPO) activities and qualities. We found that mature tobacco leaves (M3) had high substance accumulation, and the PPO activity decreased throughout the baking process. After 72 h of curing, the PPO activity in the M3 leaves was 81.22 U/g, which was significantly different from that in M1 and M2. On this basis, three different browning inhibitors (control: 10 mL of distilled water; T1:10 mL of 0.5% citric acid+0.5% polyphenol; and T2:10 mL 0.5% citric acid+0.5% salicylic acid) were sprayed onto the surface of M2 leaves before curing to observe their inhibitory effects. The T2-treated leaves showed inhibited PPO activity, and after baking for 72 h, the peroxidase enzyme (POD) content of the T2-treated leaves was higher, which effectively inhibited the enzymatic reaction. In conclusion, to reduce the browning ratio of tobacco leaves during the curing process, the harvested tobacco leaves should be allowed to reach full maturity when the values of Soil Plant Analysis Development (SPAD) chlorophyll meter ranged 9–13, and 0.5% citric acid+0.5% salicylic acid (T2) should be used as a browning inhibitor to produce tobacco with the highest sensory quality. The results of this study can help inhibit browning and maintaining the quality of the tobacco leaves during the curing process.