Microencapsulation by extrusion of an anthocyanin-based pigment extracted from açai ( Euterpe oleracea Mart.)

Abstract

Açai (Euterpe oleracea Mart.) is rich in phenolic compounds, especially anthocyanins, which are a source of the natural pigments used in the food industry as a replacement for chemical dyes. This study aimed to optimize the solid–liquid extraction of anthocyanins with effective antioxidant activity from açai and to microencapsulate the resulting pigment extract by extrusion. A central composite design was applied to evaluate the effects of extraction temperature (9.8–60.2 °C), acidified ethanol concentration (13–97% v/v) and fresh fruit:solvent ratio (1:1–1:6 g fresh fruit:mL solvent) on total anthocyanin content. A second experimental design was used to study the effects of the alginate:gelatin ratio and the anthocyanin concentration in the feed solution on encapsulation efficiency and particle size. Extraction carried out under optimal conditions of 60.2 °C, 97% v/v for acidified ethanol and 6.0 mL solvent/g fresh fruit, yielded 124.3 mg cyanidin-3-glucoside equivalents (C3GE)/100 g fruit and an extract with 88% antioxidant activity and 1163 µmol Trolox equivalents/100 g fresh fruit. Microcapsules showed an encapsulation efficiency of 99.6% and a D50 of 1378 µm at an alginate:gelatin ratio of 82.8:17.2 and 33.5 mg/L of provided anthocyanins in the feed solution. Experimental tests validated the optimization data. The optimized process thus provides a simple and low-cost route to obtain anthocyanin-rich açai pigments suitable for application as natural dyes in food and nutraceutical products.