Ultrasound-assisted extraction of betalain-rich bioactive compounds of prickly pear fruit: An optimization study

There is currently an increasing interest in obtaining bioactive components and natural pigments by novel extraction technologies. Betalains are plant-derived secondary metabolites with functional characteristics, suitable for use in food products. Conventional (CE) and ultrasound-assisted extraction (UAE) have been studied to extract betalain-rich bioactive compounds from prickly pear fruit (Opuntia ficus-indica L.). Box-Behnken design was used in response surface methodology to predict the optimal conditions for each parameter based on total betalain content (TBC), total phenolic content (TPC), and antioxidant capacity (TAC). In addition, the antimicrobial activity of the extracts at optimal conditions was investigated against Salmonella enteritidis (ATCC 13076), Escherichia coli O157: H7, and Listeria monocytogenes. Results indicated that optimal conditions for CE were achieved at 2.05-h extraction time, 50 degrees C, 80% ethanol concentration, and a 1/22.60 solid/solvent ratio, while for UAE, optimal conditions were at 30-min extraction time, 49.99 degrees C, 40% ethanol concentration, and a 1/30 solid/solvent ratio. The predicted and experimental TBC values for CE were 419.449 and 418.829 mg betalain/ kg dry matter, respectively, and for UAE, they were 472.883 and 471.818 mg betalain/kg dry matter. The extracts demonstrated antimicrobial activity solely against Salmonella enteritidis (ATCC 13076). UAE proved more efficient, extracting betalain-rich bioactive compounds in 75% less time compared to CE. Therefore, UAE emerges as a promising novel technology for obtaining natural pigments and bioactives from prickly pear.