Abstract: 【Objective】To analyze the effect of spraying compound biological agents on the quality of tobacco leaves in southern Shaanxi during the initial baking process of flue-cured tobacco,so as to provide a reference for the selection of the material ratio of compound biological agents and the regulation of the quality of tobacco leaves after curing.【Methods】The upper leaves （B2F） of Yunyan 99 was the main flue-cured tobacco cultivar in Shangluo City,Shaanxi Province,were used as the experimental materials,and three kinds of compound biological agents （SXC-4） were designed,including 5% material ratio （T1）,4% material ratio （T2） and 3% material ratio （T3）,and sprayed at the yellowing stage and final stage （42 °C） at the initial baking stage,and the chemical composition and aromatic substance content of the flue-cured tobacco leaves were determined, and the sensory evaluation and analysis were carried out.【Results】Compared with CK,the degradation effect of pectin and lignin was the best under T1 treatment,which decreased by 58.00% and 5.90%,respectively;the content of free amino acids and aromatic substances in the downstream of T2 treatment had the best effect,increasing by 6.50% and 51.80%,respectively;under T3 treatment,the contents of reducing sugar,total sugar,chrysatropic acid,degradation products of plastid pigments,phenylalanine aromatic substances and Amadori compounds content increased the most,which were 21.00%,17.00%,51.00%,54.80%,2.70% and 11.20%,respectively,and the score of sensory quality was the highest,was 60.95;pectin and lignin of T3 treatment decreased by 43.49% and 4.50%,respectively,and the content of free amino acids increased by 2.90%,the treatment effect was worse than T1 and T2 treatments.【Conclusion】The spraying of compound biological agents in the initial baking stage of flue-cured tobacco can improve the coordination of chemical components,the aroma quality and quantity of tobacco leaves,improve the transmission,reduce miscellaneous qi and thrill,improve the concentration and strength,and significantly improve the sensory quality,among which the spraying of compound biological agents with 3% material ratio can significantly improve the quality of tobacco leaves in southern Shaanxi.

Key words: Flue-cured tobacco, Compound biological agents, Quality of tobacco leaves, Initial baking stage of flue-cured tobacco