Effect of Environmentally Friendly Betalain Extraction Methods on Antioxidant Compounds of Tunisian Opuntia stricta Fruit.

Abstract

This study focuses on the extraction of betalain compounds from Opuntia stricta as a natural alternative to synthetic colorants and sustainable environmentally friendly technology solutions. Non-conventional extraction technologies including microwave (MW) and ultrasound (US) were used alone or in combination. The extraction process was conducted for both undried Opuntia stricta (OS) and dried Opuntia stricta (DOS) plant material at two distinct drying temperatures, 40 °C and 60 °C, to assess the stability of betalain molecules. The colorant's potential was evaluated by determining the betalain content, total phenolic content, and antioxidant activity. The MW (2 min) and MW (2 min) + US (10 min) extraction processes yielded the greatest betalain content in OS fresh weight (FW), with 48.54 ± 0.29 mg/100 g FW and 51.01 ± 0.16 mg/100 g FW, respectively. Furthermore, the results showed a considerable drop in betalain content when the plant material was dried at 40 °C and 60 °C, with reduction rates of 53.75% and 24.82%, respectively, compared to the betalain content before the drying process. The LC-DAD-ESI-MS analysis supported this result, revealing the presence of 17-decarboxy betanin, 17-decarboxy neobetanin, and Cyclo-dopa5-O-βglucoside in DOS at 40 °C. This study highlights the potential future in the sustainable green extraction of betalain compounds with less heat degradation to offer a stable natural colorant.