Physicochemical properties, and volatile compounds of blackened jujube vinegar as prepared by optimized fermentation process

Response surface methodology was used to optimize the fermentation factors of blackened jujube vinegar (BJV). Physicochemical properties, antioxidant activity, sensory evaluation, and volatile compounds were studied with the methods of high-performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC-MS). The results indicated that the optimal fermentation conditions was the acetic acid inoculation amount of 15%, the fermentation temperature of 30.44°C, and the initial alcohol content of 6.45% vol. During fermentation processing, there was a delay in the start of BJV fermentation and the fermentation rate was lower than red jujube vinegar (RJV). There was a significant difference in cyclic adenosine monophosphate (cAMP) content between these two (P < .05), and BJV is 3.55 times that of RJV. The content of polysaccharides in BJV and RJV decreased significantly and the trend was the same. The 5-Hydroxymethylfurfural (5-HMF) content of BJV decreased rapidly with the process and reached a very low level finally. The antioxidant activity of BJV was significantly higher than that of RJV in terms of 2,20 -azinobis (3-ethylbenzothiazoline6-sulfonicacid) (ABTS) and ferric reducing antioxidant power (FRAP) (P < .05). From sensory evaluation, the aroma and taste of BJV were better than those of RJV. There were no significant differences in the categories and quantities of volatile compounds between them. Volatile acid of BJV was less than that of RJV with the value of 72.91% and 81.15%, respectively, meanwhile, volatile esters of BJV (19.11%) was significantly higher than that of RJV (9.28%), for these reasons, sensory of BJV was softer, richer ester fragrance, and RJV was more stimulating.