烤烟烘烤过程中变黄温度对氮素代谢的影响

The effect of temperature in yellowing stage on nitrogen metabolism during tobacco leaf curing process

对烘烤期间不同变黄温度条件下主要含氮化合物变化规律的研究表明，高温变黄使蛋白质降解减慢，而低温变黄有助于蛋白质降解，因此烤后蛋白质含量表现为高温变黄＞低温变黄＞低温拉长变黄；氨基酸则相反，表现为低温拉长变黄＞低温变黄＞高温变黄。ＮＯ－３和ＮＯ－２含量在烘烤开始后同步上升，达到最高值后又下降，但烤后含量仍高于烤前；低温变黄有利于ＮＯ－３和ＮＯ－２积累，烤后含量较高。蛋白酶和硝酸还原酶活性在烘烤期间先上升后下降，呈倒“Ｖ”字型变化；高温变黄条件下酶失活性较快，缩短酶的作用时间。施氮量与烤后烟叶中蛋白质、氨基酸、ＮＯ－３和ＮＯ－２含量成正比。

Study on the change of nitrogen metabolism under different yellowing temperature during curing process indicated that the degradation of protein was obstructed under high temperature yellowing (HTY) and boosted under low temperature yellowing (LTY) and low temperature and prolonged yellowing (LTPY). The protein content in tobacco leaf cured under different yellwoing temperature condition was HTY>LTY>LTPYI the ammonia acid content was LTPY>LTY>HTY. The content of nitrate and nitrite increased quickly at the beginning of curing and decreased when the peak was reached. The content in cured tobacco leaf was still higher than in fresh tobacco leaf. The content of nitrate and nitrite in tobacco leaf cured under LTY was higher than cured under other conditions. The activity of proteinase and nitrate reductase increased at first and then decreased during curing process and the activity lost quickly under HTY The N level applied had positive correlation with the content of protein, ammonia acid, nitrate and nitrite.