Microencapsulation and accelerated stability testing of bioactive compounds of Hibiscus sabdariffa

The aim of this study was to encapsulate hibiscus aqueous extract, which has valuable content in anthocyanins with antioxidant activity. For this purpose, assays were realized using whey protein isolate and polydextrose and a mixture of both as carriers by spray-drying and freeze-drying encapsulation. Statistical analysis indicated that the powder containing only polydextrose by freeze-drying presented the best condition of encapsulation, with retentions of phenolic, anthocyanin and antioxidant activity measured by ABTS, DPPH, and HRSA of 86, 77, 76, 90 and 74%, respectively. Accelerated stability tests (75 and 90% relative humidity, at 40 and 60 °C) performed for 30 days in the powders, showed two periods of losses for polyphenols and antioxidant capacity: a significant decrease (p < 0.05) and its posterior stabilization in all storage conditions. In order to predict the degradation kinetic of anthocyanins encapsulated was used the first-order kinetic model, whose degradation rate constants ranged from 0.0259 to 0.2910 d−1, and increased with the temperature and relative humidity, with the Q10 temperature coefficient values from 1.1 to 2.1. FTIR and TGA assays indicated that the encapsulation occurred by physical incorporation, as well as up to 210 °C, powders presented high thermal stability. The results suggested that the powders may be used as a bioactive ingredient due to its high solubility and thermal stability.