From 'green' technologies to 'red' antioxidant compounds extraction of purple corn: a combined ultrasound-ultrafiltration-purification approach.

Abstract

A pilot scale process consisting of ultrasound-assisted extraction, ammonium sulfate precipitation, cross-flow ultrafiltration and AB-8 macroporous resins purification aiming to recover anthocyanins and zein from purple corn (PC) was optimized and scaled-up. The effects of five independent variables (ethanol concentration, liquid to solid ratio, ultrasound temperature, time and power) were discussed and the most influential factors were optimized. The highest total anthocyanin (0.45 ± 0.01 g kg-1 ) and zein (17.14 ± 1.73 g kg-1 ) contents from purple corn were obtained using an ultrasound power of 105 W, an extraction time of 90 min, an ethanol concentration of 74% and a liquid to solid ratio of 26:1, at 70 °C, and this was consistent with the predicted values (0.46 and 17.36 g kg-1 , for anthocyanin and zein, respectively). Subsequently, ammonium sulfate precipitation was used to isolate anthocyanins and zein. After cross-flow ultrafiltration, zein (6.30 g) was obtained with 80% purity. Anthocyanins were purified by AB-8 macroporous resins, resulting in 1.60 g of anthocyanins. High-performance liquid chromatography-electrospray ionization-mass spectrometry analysis revealed eight different anthocyanins in purple corn extracts. From the results obtained in the present study, it can be concluded that the proposed extraction-separation-filtration-purification method applied under the optimal conditions could be scaled-up to recover anthocyanins and zein simultaneously. Moreover, under the selected conditions, no significant degradation of anthocyanins was observed. © 2018 Society of Chemical Industry.