烤烟NC55不同部位叶片在烘烤过程中多酚氧化酶活性变化动态研究

刘凯 刘朋 苑亚汝 徐赛 李建东 刘成林 赵环宇 王玉军

摘要：烟草中多酚氧化酶（PPO）介导的酶促棕色化反应会影响烟叶的外观色泽，降低内在品质，导致经济效益降低。为摸清不同部位烟叶在烘烤过程中关键温度点PPO活性的变化规律，对烤烟品种NC55下、中、上三个不同部位烟叶烘烤过程中PPO活性进行了测定。结果表明：（1）整个烘烤过程中中部烟叶PPO活性呈现先升高再降低的变化规律，下、上部烟叶PPO活性则呈现先降低后升高再降低的变化规律；（2）整个烘烤过程中，中、下部位烟叶PPO活性在46℃左右时达到高峰，上部烟叶则达到第二个峰值，54℃以后各处理烟叶中PPO活性基本消失；（3）38℃之前，上部烟叶PPO活性最高，而42℃之后，中部烟叶PPO活性最高。研究结果对于优化NC55的烘烤工艺有一定指导意义。

关键词：烤烟；部位；多酚氧化酶；活性

中图分类号：S572.09文献标识号：A文章编号：1001-4942（2018）04-0025-04

Abstract Tobacco enzymatic browning reaction induced by polyphenol oxidase（PPO） can influence the exterior color of tobacco leaves， lower interior quality and reduce economic benefits. In order to find out the change regularities of PPO activities in tobacco leaves at different positions at the key temperature point during the flue-curing process， the PPO activities of NC55 leaves at upper， middle and lower parts were determined in the study. The results were as follows.（1） In the whole flue-curing process， the PPO activity of middle leaves increased firstly and then decreased， while that of the lower and upper leaves decreased firstly， then increased and decreased again. （2） The PPO activity of leaves at lower and middle position reached the peak at about 46℃，while that of the upper leaves reached the second peak.The PPO activity almost disappeared after 54℃. （3） The PPO activity of the upper leaves was the highest before 38℃， while that of the middle leaves was the highest after 42℃.The study results could provide a certain guidance for optimizing the flue-curing technology of NC55.

Keywords Tobacco； Part； Polyphenol oxidase； Activity

多酚氧化酶（polyphenol oxidase，以下简称PPO）是自然界中分布极广的一种金属蛋白酶，普遍存在于植物、真菌、昆虫的质体中。在烟草中，PPO是一种重要的酶，不仅在烟草的整个生长过程中担负着抗病、抗虫等重要的生理功能，还是烟叶酶促棕色化反应的重要参与者[1]。烟草酶促棕色化反应是指烟叶在调制、醇化和加工过程中由于酶的促进和物质转化，烟叶由黄色逐渐变棕、变褐的过程[2]。PPO在烟叶调制、醇化和加工过程中将多酚类物质氧化成醌类物质，这些醌类物质与氨基酸以及蛋白质等聚合生成分子量不等、颜色各异的深色物质，严重影响烟叶质量，降低经济价值[2]。……