Techno-economic evaluation of the extraction of anthocyanins from purple yam (Dioscorea alata) using ultrasound-assisted extraction and conventional extraction processes

Abstract

Anthocyanins have high antioxidant activity. Purple yam (Dioscorea alata) is a common plant found in tropical countries and could be a valuable source of anthocyanins. Ultrasound-assisted extraction (UAE) increases the extraction yield using reduced extraction times, low temperatures, and solvents that are considered safe. This study aims to obtain ethanolic anthocyanin-rich extracts from purple yams. The effects of temperature (30 °C and 60 °C), extraction time (10 and 30 min), amplitude (20% and 60%), and ethanol-to-water ratio (80:20 and 50:50) were evaluated. The global extraction yield (GEY) and monomeric anthocyanin content (MAC) were determined; the GEY varied between 14.9% and 22.6%, while the MAC ranged between 1.44 ± 0.04 mg and 0.44 ± 0.04 mg Cy3GlE/g DR obtained in the UAE process. Results indicate that the optimum extraction conditions are 60 °C for 10 min with 60% amplitude and an ethanol-to-water ratio of 80:20. The economic evaluation was performed using SuperPro Designer® software (v. 8.5). A two-extractor system with capacities of 5, 50, and 500 L was considered. The cost of manufacturing (COM) decreased from US$ 950.52 kg−1 to US$ 124.08 kg−1 when the extractor capacity increased from 5 l to 500 l. Results of the sensitivity study show that the extraction of anthocyanins from purple yam by UAE is economically feasible when the selling price is above US$170 kg−1. UAE is a feasible technique for obtaining anthocyanin-rich extracts from purple yam.