Effect of thermal processes on roselle anthocyanins encapsulated in different polymer matrices

Abstract

The stability of roselle anthocyanins was investigated under three different heat treatments (60, 80 and 98C). The dry red powder from roselle calyces was produced using spray-drying technique using four different encapsulating agents, i.e., maltodextrin, gum arabic, a combination of maltodextrin and gum arabic, and soluble starch. The four types of matrices increased the half-life of the pigments during heat treatment, especially at 98C (P < 0.05), compared with the roselle extract as the control. Heat treatment results showed that the combination of maltodextrin and gum arabic had the lowest degradation kinetic rates at 60 and 80C. Arrhenius parameters' results further confirmed that the degradation of anthocyanins was strongly dependent on the operating temperatures during heat treatment. In this study, all encapsulating agents, except the soluble starch, largely elongated the half-life of roselle anthocyanins compared with the nonencapsulated anthocyanins. A spectrum of natural, red-hue primer colorants is derived from roselle plant extracts, which is substantially free of alkaloids, enzymes, aroma or solvent residuals, and is microencapsulated to ensure good stability and shelf life. This study measured the thermal stability and suitability of the microencapsulated natural colorants. The colorants are for functional use in the food, pharmaceuticals, cosmetics and other industries.