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291 samples of flue-cured tobacco leaves from main tobacco-growing areas of China were used as materials to analyze the distribution of volatile acid and volatile alkali; The variation of volatile alkali and volatile acid among different tobacco-growing areas, provinces, stalk position, years, cultivars and aroma styles; The relationship with volatile acid and volatile alkali content, neutral aroma components and sensory evaluation. Main results were as follows:1. The volatile acid content were medium or relatively low, the average of it was 0.24%, range of it was 0.11%~0.46%, only 52 samples (17.9% of all ) were among the suitable range. The range of volatile alkali was 0.12%~0.49%, the average of it was 0.27%, about 38.5% volatile alkali content were suitable.2. The results of variation analysis showed: widely variation of volatile acid content among different tobacco-growing areas, provinces, years, but there were no significant differences among stalk position, cultivars, aroma style. Content of volatile acid in North were significantly lower than the 4 areas, but the differences of volatile acid content of them were not significant; volatile acid content of Hunan(0.29%) were significant highest among provinces, Henan took second place, the rest provinces had no significant differences; volatile acid content(0.31%) 0f 2000 were significantly higher than 2000~2005.There were significantly differences in volatile alkali content among different tobacco-growing areas, provinces, stalk position, aroma style, but it was stable among cultivars, years. Volatile alkali content of Huanghuai was relatively low, while southeast, volatile alkali content of Middle and Upper Yangtze River were suitable, average of it was 0.31%, and there was no significant differences between them and Beifang; Among provinces, volatile alkali content of Hunan, Fujian, Jiangxi and Chongqin were suitable, and significantly higher than the rest provinces, average was 0.32%~0.37%, but they had no significances, Henan and Heilongjiang were significantly low, just 0.21%; lower leaf > middle leaf > upper leaf among stalk position; Strong aroma style (0.30%) were highest, Delicate aroma style (0.29%) took second place, Midterm aroma style (0.26%) were lowest among aroma style, but there were no significant differences between Strong aroma style and Delicate aroma style.3. Simple correlation between volatile acid and chemical components indicated that: volatile acid content of upper leaf had significant negative correlation with reducing sugar and total sugar, had extremely significant negative correlation with pH; volatile acid content of middle leaf had significant positive correlation with potassium content and significant negative correlation with pH; volatile acid content of lower leaf had no significant correlation with chemical components.Simple correlation between volatile alkali and chemical components showed that: volatile alkali content of upper leaf had extremely significant positive correlation with potassium, petroleum ether extract, total alkaloids, total nitrogen and soluble protein content, had extremely significant negative correlation with the content of starch, reducing sugar, total sugar and pH; volatile acid content of middle leaf had extremely significant positive correlation with total alkaloids, chlorine, total nitrogen, petroleum ether extract and soluble protein content, had extremely significant negative correlation with total nitrogen and petroleum ether extract content.4. By applying cluster analysis, variance analysis and simple correlation, the relationship between volatile acid as well as volatile alkali content and main neutral aroma components of flue-cured tobacco leaves were studied. The results indicated that:(1) There were no significant differences in several neutral aroma components among 3 volatile acid groups except products degraded by phenylalanine. Degraded by phenylalanine added with the increase of volatile acid content, degraded by phenylalanine were highest when the volatile acid in medium volatile acid groups (0.23%~0.30%). Simple correlation indicated that: volatile acid had extremely significant positive correlation with degraded by phenylalanine and degraded by carotene, significant positive correlation with neoplytadiene and total content of volatile aroma matter when the volatile acid content were low; The correlation between volatile acid and neutral aroma components was not significant when the volatile acid content were medium or high.(2)There were extremely significant differences in products degraded by phenylalanine, products of maillard reaction, products degraded by cembrane, products degraded by carotene, neoplytadiene and total content of volatile aroma matter among 3 volatile alkali groups. While the volatile alkali contents increased, products degraded by phenylalanine, products of maillard reaction, products degraded by cembrane, products degraded by carotene, neoplytadiene and total content of volatile aroma matter gradually enhanced, and the contents of them were highest in high volatile alkali group(0.34%~0.49%). Simple correlation showed that: volatile alkali contents had extremely significant positive correlation with degraded by phenylalanine, significant positive correlation with products degraded by cembrane when the volatile acid contents were low; the volatile acid contents had significant positive correlation with products degraded by carotene when the volatile acid contents were medium; the volatile acid contents had significant positive correlation with degraded by phenylalanine, products degraded by carotene, neoplytadiene and total content of volatile aroma matter.5. By applying variance analysis and regression analysis, the relationship between volatile acid as well as volatile alkali content and sensory evaluation of flue-cured tobacco leaves were studied. The results showed that:(1)There were no significant differences in aroma characteristics, smoke characteristics, taste characteristics and smoking total scores among 3 volatile acid groups except combustion characteristics. The scores of combustion characteristics were significantly highest (11.72) when the volatile acid contents added to 0.34 %( high volatile acid group). Besides, the regression equations of volatile acid and combustion characteristics reached a significant level at 5%.There were no significant differences in quality of arom, volume of aroma, undesirable taste, physiological strength, taste concentration, after taste, biting taste, ash color among 3 volatile acid groups except combustibility. Combustibility gradually enhanced with the increase of volatile acid, then got the highest scores (6.30) in high volatile acid group. The regression equations of volatile acid and taste concentration, combustibility reached a significant level at 5%.(2) There were extremely significant differences in smoke characteristics, taste characteristics, combustion characteristics among 3 volatile alkali groups. Besides, scores of smoke characteristics gradually enhanced with the increase of volatile alkali, then got the highest scores (11.77) when the volatile alkali contents added to 0.38%; scores of taste characteristics and combustion characteristics decreased with the increase of volatile alkali. Besides, the regression equations between taste characteristics and volatile alkali, between combustion characteristics and volatile alkali, between smoke characteristics and volatile alkali reached a significant level at 1%.Volume of aroma, physiological strength score and taste concentration score increased when the volatile alkali content added, and got the highest scores (5.97、5.78、5.99)in high volatile alkali group; ash color scores first increased then decreased with the increase of volatile alkali content, the scores(5.50) were highest in medium group (0.24%~0.33%) of volatile alkali. When the volatile alkali content increased, undesirable taste score, after-taste score, biting taste score and combustibility score decreased. Besides, the regression equations of volume of aroma, undesirable taste, and physiological strength, taste concentration, after taste, biting taste, ash color, and combustibility with volatile alkali all reached a significant level at 1%.
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