Effects of ethanol extraction and acetic acid fermentation on the functional properties of roasted coffee beans

This study evaluated the effect of acetic acid fermentation added to coffee concentrate using the concentrate of fermented coffee bean ethanol extract. The ethanol concentration that can extract a high content of coffee’s active ingredients (caffeine, chlorogenic acid) was 50% (v/v). The ethanol extract from coffee was concentrated to a solid content of 7.94% (w/v) and added at a concentration of 7-10% to prepared coffee liquor containing 6% ethanol. Additionally, 20% seed vinegar was introduced to initiate acetic acid fermentation. During the fermentation period of coffee vinegar with different concentrations of coffee extracts (CVCE1-CVCE4) lasting 30 days, the viable cell counts, physicochemical properties (soluble solid contents, pH, and total acidity), organic acids, free sugars, and ethanol content were measured. The number of viable cells was 4.50-7.33 log CFU/mL on the 10th day of fermentation, and the growth of bacteria tended to decrease as the content of coffee solids increased. As acetic acid fermentation progresses, the ABTS and DPPH radical scavenging activities of coffee vinegar decreased, while pancreatic lipase inhibition activity increased. The analysis showed that the amount of coffee extract concentrate added affects the fermentation characteristics of acetic acid bacteria, resulting in a difference in the functionality of coffee vinegar.