Extraction Optimization and Microencapsulation of Anthocyanins from Okra Flowers: Utilizing Plant Waste as a Source of Bioactive Compounds

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 degrees 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.