Preparation, chemical profiles, antioxidative activities, and angiotensin‐converting enzyme 2 inhibitory effect of date fruit vinegar

Date palm (Phoenix dactylifera L.) is an important commercial crop extensively consumed as a staple food and has been applied in many ethnomedical systems. Fruit vinegar is a preservative, condiment, and beverage with a spectrum of health benefits. Studies about the preparation, chemical profiles, and bioactivities of date fruit vinegar (DFV) are fundamental requirements for industrialization production. This study focused on the lab-scaled producing conditions, chemical profiles of DFV, and its bioactivities in vitro. According to the results, a date wine containing 9.75% methanol was obtained by yeast fermenting the enzyme-hydrolyzed date juice with 23.11% ± 0.39% of total sugar content. The optimized acidic fermentation conditions were an inoculation amount of 0.02%, a fermentation temperature of 31.14°C, and an initial alcohol content of 7.78%. Total acidity and total phenolic contents of the DFV were 7.74% ± 0.29% and 1.44 mg gallic acid equivalent/mL, respectively. In total, 32 organic acids were quantitated in the unaged DFV, with acetic, L-malic, and oxoglutaric acids as the predominant compounds. A total of 930 volatiles were identified in the DFV, including 186 esters, 177 terpenoids, and 148 heterocyclic compounds. There are 18 phenolic acids presented in the DFV. In addition, 42 flavonoids were quantitated in the DFV, including catechin, taxifolin, and cynaroside. The results of free radical scavenging activities and reducing power demonstrated that the DFV displayed good antioxidant properties. The DFV also acted well on angiotensin-converting enzyme 2 inhibition. These results suggest that the DFV can be industrially developed as a dietary supplement.