Application of PLSR in correlating sensory and chemical properties of middle flue-cured tobacco leaves with honey-sweet and burnt flavour

Among the eight types of aroma and flavour characteristics of Chinese flue-cured tobacco (FCT), tobacco grown in Shandong is classified as having a honey-sweet and burnt aroma. To elucidate the key chemical components that determine the characteristics of the honey-sweet and burnt aroma styles of Shandong FCT, we qualitatively and quantitatively evaluated the smoke flavour quality and five categories of flavour-related chemical components (routine components, water-soluble sugars, free amino acids, Amadori compounds and key aroma-active compounds) in Shandong middle FCT leaves using sensory analysis and modern instrumental analysis techniques. The association between the chemical components and sensory quality was analysed. Our results showed that the total sugars, reducing sugars (fructose, glucose, and psicose), total sugar-nicotine ratio, proline-total amino acid ratio, sulphur-containing amino acid-total amino acid ratio and fructosyl-proline (Fru-Pro) were high in premium FCT leaves. The aroma-active compounds associated with the honey-sweet burnt flavour style of the Shandong Middle FCT included sweet-scented 2,3-pentanedione, 2,3-butanedione, butyrolactone, 2-furanmethanol, roasted-like 2-pentylfura, and green-like 1-penten-3-one. Partial least squares regression (PLSR) analysis revealed that 29 aroma precursors were positively correlated with the sensory quality characteristics of Shandong FCT. The results of our study can provide guidance for the targeted improvement and precise regulation of the flavour-style characteristics of Shandong FCT.