Effects of earlier harvesting on the quality and style characteristic of fresh-sweetness flavor type flue-cured tobacco upper leaves

【Objective】 The effects of earlier harvesting on the quality and style characteristics of fresh-sweetness flavor type flue-cured tobacco upper leaves were explored to provide reference for improving the quality and highlighting the style characteristics of fresh-sweetness flavor type of flue-cured tobacco upper leaves in Guizhou. 【Method】 Yunyan 87 upper tobacco leaves used as experimental material，the effects of different harvesting times and maturities（CK，normal harvesting/mature；T1，4 d earlier harvesting/ just mature；T2，8 d earlier harvesting/immature）on the appearance quality，fragrance substance content and sensory quality were studied，and the substance basis of the style characteristics manifestation of fresh-sweetness flavor type flue-cured tobacco upper leaves in Guizhou was analyzed. 【Result】 With the earlier of harvesting time and the decrease of maturity，the appearance quality of flue-cured tobacco upper leaves became worse，mainly showing in the aspects of color，maturity and leaf structure. Compared with CK，the total scores of fluecured tobacco leaf appearance quality evaluation of T1 and T2 treatments decreased by 8.33% and 22.92% respectively. T1 treatment could significantly increase the content of carotenoid degradation products，Maillard reaction products，aromatic amino acid degradation products，cemdrenoids degradation products，fatty acid substances，unclassified fragrance substances，total fragrance substances（except neophytadiene）and total fragrance substances（P<0.05，the same below）， among them，total fragrance substances increased by 7.54%. In addition，it was beneficial to highlight the style characteristics of fresh-sweetness flavor type flue-cured upper tobacco leaves with the evaluation score increased by 3.64%. However，T2 treatment was not conducive to highlight the style characteristics of tobacco leaves，with the total fragrance substances content of flue-cured tobacco leaves increased by 4.27%. Six kinds of plastid pigment degradation products（safranal，β-damascenone and megastigmatrienone Ⅰ-Ⅳ），three kinds of aromatic amino acid degradation products（phenylethyl acohol，phenyl acetaldehyde and 2-methoxy-4-vinylphenol）and two kinds of unclassified aroma substances（trans- 3-hexen-1-ol and nonanal）were screened and mainly characterized by the fresh-sweetness flavor type of tobacco leaves. Moreover，2 kinds of Maillard reaction products（decanal and 1-（1H-pyrrol-2-yl）-ethanone），and 1 kind of cemdrenoids degradation product（solanone）were mainly characterized by the grass flavor type of tobacco leaves. In addition，2 kinds of fatty acid substances（palmitic acid and methyl linolenate）were mainly characterized by the sweetness flavor type of tobacco leaves. The total scores of sensory quality evaluation of CK and T1 treatment were significantly higher than that of T2 treatment，with an increase of 7.57% and 7.41% respectively. Industrial availability and formula suitability of CK and T1 treatment were one grade/level higher than that of T2 treatment. 【Conclusion】 It is beneficial to improve the fragrance content and manifestation of the style characteristics of tobacco leaves with 4 d earlier harvesting. Moreover，a total of 16 kinds of marker substances that highlighting style characteristic of fresh-sweetness flavor type are screened. However，4 d earlier harvesting is not conducive to the improvement of appearance quality of flue-cured tobacco upper leaves. In addition，8 d earlier harvesting has the poor overall quality of flue-cured tobacco upper leaves. Therefore，earlier harvesting of upper tobacco leaves of fresh-sweetness flavor type in Guizhou should adjust the corresponding curing parameters according to the tobacco leaves.