Differences in free amino acid contents between flue-cured tobacco and burley tobacco both cured with flue-curing and air-curing method.
Amino acids are the important precursors of Maillard reaction compounds, and the significant differences in individual amino acid content were measured between different tobaccos. The experiments were conducted in 2010 with a flue-cured tobacco (Hongda) and a burley tobacco (TN86) to investigate the amino acid contents these two tobaccos under two N treatments and two curing method. The results demonstrated that by using the same curing method the contents of proline (Pro) and methionine (Met) were not different in the two types, while the contents of Pro and Met in tobacco cured by the flue-cuing method increased more than 112% and 91%, respectively, over tobacco cured by the air-curing method. Pro and Met were most influenced by curing method and not tobacco type. Contents of free amino acids in burley tobacco were higher than that in flue-cured tobacco and the free amino acids most influenced by genotype were aspartic acid (Asp) and glutamic acid (Glu). Content of Asp in burley tobacco was more than 5 times higher than that in flue-cured tobacco under the same applied nitrogen Contents of Asp and Glu were not altered by curing method. All of the free amino acids increased with increased N application. Conclusions are that flue-curing is the main cause of higher amounts of Pro and Met in flue-cured tobacco, while genetic factors contribute more to the high levels of Asp and Glu in burley tobacco.