Optimization of Ultrasound-Assisted Extraction of Anthocyanins and Phenolic Compounds from Black Soybeans (Glycine max L.)

Abstract

Black soybeans have been reported to contain high antioxidant content, including anthocyanins. Ultrasound-assisted water extraction of antioxidants from Korean black soybeans (Glycine max [L.] Merr. Cheongja4ho) was investigated for the first time. A three-level, three-factor Box-Behnken design using a response surface methodology (RSM) was employed to optimize the conditions for the maximum yields of three dependent variables, including total anthocyanin content, total phenol content, and 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging activity, based on 17 different experiments. The solid-liquid ratio (X1, 1/30–1/50 g mL−1), extraction time (X2, 1–9 min), and amplitude (X3, 20–100%) significantly affected three dependent variables. The optimized conditions were solid-liquid ratio of 49.1 g mL−1, extraction time of 8.59 min, and amplitude of 81.4%. At the optimum point, the total anthocyanin content, total phenol content, and ABTS•+ scavenging activity were 66.44, 940.96, and 242.45 mg 100 g−1. The difference (%) between the predicted and experimental values was less than 6.40%, indicating that the model fits well. The conditions optimized for ultrasound-assisted water extraction of antioxidants from black soybeans can be applied as an efficient technique for extracting anthocyanins in plants on a larger scale.