Encapsulation of roselle anthocyanins in blank alginate beads by adsorption and control of anthocyanin release in beverage by coatings with different molecular weight chitosan

In this study, the encapsulation of roselle anthocyanins was improved by immersing blank alginate beads in concentrated anthocyanin extracts. When increasing the alginate concentration (1–3%) and the anthocyanin concentration in the soaking solution (0.1–1.0 g/L), the phenolics, flavonoids, and anthocyanins gradually adsorbed to the matrix over time and peaked at 84–108 hr, leading to higher antioxidant activities. Before added to an acidic beverage, 3% alginate hydrogels soaked in solution of 1.0 g/L after 84 hr were coated using two types of chitosan with low and medium molecular weight. The results showed that low-molecular weight chitosan was superior to medium-molecular weight chitosan in limiting the diffusion of anthocyanins into beverage. The release rates of anthocyanins into beverage were in descending order: control > medium-molecular weight chitosan > low-molecular weight chitosan, as illustrated by the time required for anthocyanins to reach an equilibrium state being 1, 150, and more than 400 hr, respectively. Novelty impact statement Blank alginate gels were soaked in the concentrated roselle solution for anthocyanin adsorption. The antioxidant contents and activities increased at higher alginate and anthocyanin concentrations in the soaking solution and peaked at 84–104 hr. Low-molecular weight chitosan coating reduced the rate of anthocyanin release from beads into acidic beverages.