Effect of Air Humidity on Nicotine to Nornicotine Conversion during Burley Tobacco Air-curing

By controlling the air humidity during yellowing and browning stage,the effect of humidity on nicotine to nornicotine conversion in burley tobacco were studied.The results showed that the rate of nicotine conversion(RNC)in midrib of high-converter was higher than that in lamina under different air humidity,it was also true of non-converter,except for the fifteenth leaf of B21 cured under low air humidity.The nicotine content in high-converter lamina treated under low air humidity was the highest,while that in non-converter lamina was dependent on varieties and stalk positions.Lower air humidity was of benefit to decreasing the RNC in lamina of high-converter or non-converter.The effect of air humidity on the contents of nicotine,nornicotine and RNC in midrib varied in different varieties.Therefore,timely reducing air humidity during curing would be beneficial to reducing the nornicotine content in tobacco leaf.