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This study focuses on optimizing the ultrasound-assisted extraction (UAE) of bioactive compounds from purple-fleshed sweet potatoes (PFSP) for potential use as natural colorants. Factors such as time, temperature, and solid-to-liquid ratio were varied using a Box–Behnken Design. The optimal conditions were determined as 75 min, 70 °C, and a 1:15 m/v solid-to-liquid ratio, resulting in 18.372 mg/100 g total anthocyanin (TA) and 151.160 mg GAE/100 g total phenolic content (TPC). The validation yielded 18.822 mg/100 g for total anthocyanin and 162.174 mg GAE/100 g for total phenolic content, showing a 7% difference from predictions. UAE significantly increased TA extraction by 81% and TPC by 93% compared with the conventional method, with a notable reduction in process time from 24 h to 75 min. Additionally, three kinetic models were tested to compare extraction mechanisms, confirming the efficiency of UAE for PFSP bioactive compound recovery. This study proposes the UAE technique as a highly effective means of extracting bioactive compounds from PFSP, offering promising applications across multiple industries.

ABSTRACT: This study aimed to optimize the ultrasound-assisted extraction (UAE) of total anthocyanins from two stages of ripening purple tomatoes (low and high) and to compare the optimized extraction with the conventional one. In the optimization of UAE, the studied variables were time (5 to 75 min), temperature (30 to 70 °C), and solid: liquid ratio (1:5 to 1:15 m/v). The optimal condition of the UAE process, for low-ripened purple tomatoes, occurs at a time of 75 min, temperature of 40 °C, and solid: liquid ratio of 1:15 m/v, predicting the content of 12.487 mg/100g. For high-ripened purple tomatoes, the optimal condition occurs at a time of 40 min, temperature of 50 °C, and solid: liquid ratio of 1:15 m/v, predicting the content of 8.802 mg/100 g. On validation of these optimized conditions, less than a 3% difference was reported between the predicted and experimental values (12.267 mg/100 g for low-ripened, and 8.894 mg/100 g for high-ripened purple tomatoes). When comparing the optimized UAE with the conventional extraction, it was observed that UAE increased (P < 0.05) the extraction of total anthocyanins content by 73% for low-ripened and by 54% for high-ripened purple tomatoes. Thus, the study indicated that the UAE is an efficient technology for recovering bioactive compounds from purple tomatoes.