Study on ultrasound-assisted extraction of cold brew coffee using physicochemical, flavor, and sensory evaluation

Cold brew coffee is popular with consumers due to its simple preparation and unique taste. However, traditional cold brew coffee extraction is time consuming and inefficient, which can be improved by ultrasound-assisted extraction to enhance the product market potential. In this study, the flavor profiles and sensory differences of coffee prepared at three different ultrasonic temperatures, as well as traditional cold brew and hot brew coffee, were evaluated by consumer-based sensory evaluation, Rate-All-That-Apply, combined with the determination of the content of volatile and non-volatile components. The results showed that ultrasound assisted cold brew coffee prepared at 25 °C had a good extraction effect, with chlorogenic acid (CGA) and organic acid contents of 1.05 mg/mL and 0.97 mg/mL, respectively, which were higher than the traditional cold brew coffee obtained after 12 h of preparation, with contents of 0.53 mg/mL and 0.85 mg/mL, respectively. And the total content of volatile compounds can almost reach the results of traditional cold brew for 12 h, which were 1.25 mg/kg and 1.42 mg/kg, respectively. Sensory evaluation indicated that ultrasonic treatment enhanced the sensory attributes such as nutty and cocoa flavors in the coffee. Consumers preferred the cold brew coffee obtained via ultrasound-assisted extraction. These samples presented higher levels of sweetness, floral, and fruity flavors, which were associated with 2,5-Dimethyl-3-(2-methylpropyl)pyrazine, 2,3-Dimethyl-5-(3-methylbutyl)pyrazine, (S)-(+)-4-sec-Butylpyrazole, and styrene. In this study, we demonstrated that ultrasound-assisted extraction can help reduce the time to prepare cold brew coffee and make it possible to commercialize ultrasound-assisted cold brew coffee.