烤烟密集烘烤变黄期类胡萝卜素及其降解香气成分的变化

 【目的】研究密集烘烤变黄阶段烤烟类胡萝卜素组分、酶活性及其降解香气成分含量的变化,为密集烤房烘烤工艺优化和完善提供理论依据。【方法】采用河南农业大学设计的电热式温湿自控密集烤烟箱,研究不同温湿度条件对变黄期烤烟类胡萝卜素各组分降解、相关酶活性变化及其降解香气成分含量的影响。【结果】变黄期类胡萝卜素(β-胡萝卜素、叶黄质、新黄质、紫黄质)含量均随烘烤过程推进而逐渐降低。其中低温低湿变黄(T1)和低温中湿变黄(T2)β-胡萝卜素在变黄结束时含量较低,其值分别为17.14 μg?g-1 FW、19.00 μg?g-1 FW。叶黄质、新黄质、紫黄质含量在各处理中随温湿度的降低而降低。低温变黄处理β-胡萝卜素与叶黄素(叶黄质、新黄质、紫黄质)的比例和烤前相比均有所升高,高温变黄处理则与之相反。不同处理叶黄质与叶黄素的比例和烤前比均升高,而新黄质和紫黄质则与之相反。烤后烟叶T1、T2处理类胡萝卜素含量较低,尤其是T2处理,其值为76.31 μg?g-1。烤后烟叶类胡萝卜素降解香气成分含量以T2处理最高,为87.5634 μg?g-1,其次为T1处理,为81.1192 μg?g-1,显著高于其余处理。变黄期T1、T2处理有利于脂氧合酶(LOX)、过氧化物酶(POD)活性的充分表达,使类胡萝卜素降解更充分。相关分析表明,烘烤中变黄期POD活性与类胡萝卜素各组分呈显著正相关。【结论】变黄期低温和相对较低的湿度条件下,保持相对较高的酶活性,使LOX与POD之间的协同拮抗作用达到一种动态平衡,并在36—48 h适当延长相对较长的时间,对充分降解类胡萝卜素物质和改善烟叶香气品质是有利的。

The Degradation Mechanism of Carotenoids in Flue-Cured Tobacco and the Changes of the Related Aroma Components in the Yellowing Stage During the Bulk Curing Process

【Objective】 The changes of the contents of carotenoids components, the related enzymes activities, and the aroma components degraded by which in flue-cured tobacco in the yellowing stage during the bulk-curing process were studied in order to provide a theoretical basis for optimization and perfection of curing technology. 【Method】 The effects of different temperature and humidity conditions on the degradation of carotenoids, the related enzymes activities in the yellowing stage and the contents of aroma components in flue-cured tobacco during the bulk curing process were studied by using the electric-heated flue-curing barn designed and made by Henan Agricultural University. 【Result】 The results showed that the contents of carotenoids (β-carotene, lutein, neoxanthin, violaxthin) decreased gradually in the yellowing stage during the bulk curing process. At the end of yellowing stage the β-carotene contents of low temperature with low humidity (T1) and low temperature with middle humidity (T2) treatments were lower than others and the value of them were 17.14 μg?g-1 FW, 19.00 μg?g-1 FW, respectively. The contents of the lutein, neoxanthin, violaxthin decreased gradually in the yellowing stage following the decrease of temperature and humidity. The proportions of the β-carotene to the xanthophylls (lutein, neoxanthin, violaxthin) of the low temperature treatments at the end of yellowing stage were higher than fresh sample, on the contrary, high temperature treatments were lower. The proportions of the lutein to the xanthophylls of different treatments were higher than fresh sample, on the contrary, neoxanthin and violaxthin were lower. The carotenoids contents of T1, T2 treatments were relatively lower than others’, especially the T2 treatment, and its value was 76.31 μg?g-1 in flue-cured tobacco. The contents of aroma components of T2 treatment was the highest and its value was 87.5634 μg?g-1 in flue-cured tobacco while the content value of T1 treatment was 81.1192 μg?g-1, secondly. Both of them were higher than others obviously. The activities of lipoxygenase (LOX) and peroxidase (POD) could express fully under the T1, T2 treatments in the yellowing stage meanwhile the carotenoids degraded fully. Correlation analysis showed that the activities of peroxidase and the carotenoids components were highly significant in the yellowing stage during the bulk curing process. 【Conclusion】 If the high activities of lipoxygenase and peroxidase were prolonged longer appropriately at 36-48 h under low temperature and relatively low humidity in the yellowing stage and the effect between the cooperative and antagonism reach dynamic balance, it would be benefit to degrade carotenoids sufficiently and improve the aroma quality of tobacco leaves.