Fermentation of celery (Apium graveolens L.) with Lactobacillus plantarum NCU116: Impact on physicochemical properties, free amino acids, and volatile aroma compounds

Lactic acid bacteria (LAB) fermentation has been demonstrated to enhance the flavor and nutritional composition of vegetables. In this study, the physicochemical properties, amino acids and aroma compounds of celery were systematically analyzed during the Lactobacillus plantarum NCU116 ( L. plantarum NCU116) fermentation. Significant changes in its physicochemical properties were observed predominantly within the first 24 h. Then, the total amino acid in the celery significantly decreased from 4.52 to 3.73 mg/L. The content of total sugar and reducing sugar decreased steadily by 85.33 % and 82.61 %, respectively. In addition, a total of 65 volatile compounds, including 5 alcohols, 29 terpenoids, 3 aldehydes, 2 acids, 3 ketones, 4 alkenes, and 13 esters, were identified. Fermentation progress significantly increased the diversity and content of alcohols, aldehydes and alkanes. Further analysis revealed that 18 key aroma compounds (ROAV > 1), including trans-2-octen-1-ol, copaene, terpinen-4-ol, and linalool, significantly contributed to the fruity and woody aroma profile of fermented celery and conferred the fruity and woody aromas. Moreover, the result of sensory evaluation demonstrated that the increase in the concentration of the above compounds during fermentation contributes to the sensory characteristics. The study indicates that fermentation is a promising approach to improve the flavor of celery. • The volatile flavor of celery during fermentation was evaluated by E-nose and HS-SPME-GC-MS. • The increase of umami amino acids and the decrease of bitter amino acids greatly enhanced the flavor of celery. • Trans-2-octen-1-ol, copaene, terpinen-4-ol, and linalool played a crucial role. • Fermentation progress significantly increased content of alcohols, aldehydes and alkanes.