Microencapsulation of Hibiscus sabdariffa L. Calyx Anthocyanins with Yeast Hulls

Yeast hulls, due to their specific thin mannoprotein layer and high content of β-glucan, constitute a promising material to stabilise the colour of anthocyanins. This study evaluates the potential of yeast hulls on the freeze-drying encapsulation of anthocyanins-rich extract from Hibiscus sabdariffa L. calyx with comparison to maltodextrin microcapsules. The moisture content (5.28-16.38%), water activity (< 0.039-0.307) and hygroscopicity (17.50-25.99 g/100 g) of obtained powders were evaluated. The stability of encapsulated anthocyanins, monitored through the total anthocyanin content, was evaluated with the pH differential method immediately after production and after a 10-week storage under different conditions of temperature (5 or 37 °C), humidity (45 or 85% RH), in presence or absence of light. The colour parameters (a, b*, L*, C*, H°, ΔE^*) of powders were measured. The results indicated that yeast-hulls showed a good ability to protect anthocyanin against the influence of temperature, light, moisture compared to freeze-dried anthocyanins-rich extracts (p < 0.05). Yeast hulls protected anthocyanin better than maltodextrin under high humidity conditions (p < 0.05).