Effects of Drying Methods on the Reducing Sugars and Free Amino Acid Contents of Tobacco Flowers

To develop the utilization value of abandoned tobacco flowers in tobacco flavorings, seven drying methods were investigated to study the effects on the content of reducing sugars and free amino acid of tobacco flowers. The results were as follows: (1) The content of reducing sugars and 19 total free amino acids in tobacco flowers treated with different drying methods ranged 2.44%-15.2% and 25.6-68.8 mg/g, respectively. Asn was the most abundant amino acid, with a percentage of 33.9%-84.2%. (2) The content of reducing sugars is significantly negatively correlated with Asn, Asp, His, and total amino acid content, but positively correlated with the content of Met and Leu. (3) Based on the results of comprehensive analysis of variance, principal component analysis, and cluster analysis, the seven drying methods of tobacco flowers were clustered into four categories: Ⅰ (Air drying), which is characterized with the highest content of Asn, Asp, His and total amino acids in tobacco flowers, but the lowest content of reducing sugars and the total amount of 18 amino acids except for Asn; Ⅱ(Freeze drying), which is featured with the highest content of reducing sugars but the lowest total amount of amino acids; Ⅲ(Sun drying, 59 ℃ and 65 ℃ constant temperature drying respectively), which is distinguished by a moderate level of reducing sugars and amino acids in sun dried tobacco flowers, and by a content of reducing sugars lower than that in freeze-dried one , and the content of total amino acids higher than that of freeze-dried tobacco flowers in constant temperature dried tobacco flowers; Ⅳ(Program heating up 59 ℃ and 65 ℃ drying respectively), which is typified by a significant higher total amount of 18 amino acids except for Asn and a higher content of reducing sugars than those of the air dried one. Additionally, the total amino acid content of dried tobacco flowers at 59 ℃ was significantly higher than that at 65 ℃, but the difference in reducing sugar content was not significant. Taking into account the cost and contents of targeted quality-related component composition, air drying, sun drying, or programmed heating up 59 ℃ drying were recommended for tobacco flowers drying.