Extraction optimization and microencapsulation of anthocyanins from okra flowers: Utilizing plant waste as a source of bioactive compounds
Hojjat Pashazadeh, Ali Ali Redha, Joel B. Johnson, İlkay Koca
Abstract
Okra ( Abelmoschus esculentus ) flowers are a common agriculture by-product across regions in Africa, Asia and the Americas; however, they have considerable value-adding potential as rich sources of health-benefitting anthocyanins. One major barrier standing in the way of this potential is the high pectin content, resulting in viscous extracts which are difficult to process. In this study, a response surface methodology approach was used to optimize the extraction process (extraction time, temperature and solvent) of anthocyanins (total anthocyanins, cyanin, cyanidin-3-rutinoside and cyanidin-3-glucoside) from okra flowers. This procedure was used to maximize the anthocyanin yield while maintaining an acceptable viscosity. The optimized conditions were an extraction temperature of 60 °C, extraction time of 40.5 min, and solvent volume of 85 mL (for 2 g of dried powder). Rheological testing revealed that the extract acted as a non-Newtonian fluid but was not overly viscous. The three drying methods tested (freeze-drying, microwave-drying and spray-drying) all showed very high efficiency for microencapsulation (>99%); however, freeze-drying yielded the best anthocyanin bioaccessibility. This optimized extraction procedure may be useful for exploiting okra flowers as a rich source of bioactive anthocyanins that can be utilized as functional food ingredients.