Microencapsulation of anthocyanin extract from purple rice bran using modified rice starch and its effect on rice dough rheology

Abstract

The investigation aims to microencapsulate anthocyanin extract from purple rice bran with modified glutinous rice starch to provide stable anthocyanin powder. The modified glutinous rice starch was used as wall material where anthocyanin extract was a core material for microencapsulation. The microencapsulation was carried out in a spray dryer, and the process was optimized using a rotatable central composite design. The effect of independent parameters, viz., starch concentration, inlet air temperature, and atomizer pressure, on the dependent parameters, such as encapsulation efficiency, anthocyanin content, 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging activity, true density and water activity were investigated. The optimum values of the spray drying process parameters were 6.01% of starch concentration, 168.78 °C inlet air temperature and 4.96 MPa atomizer pressure. The physical characteristics of spray-dried powders were investigated in term of water activity (0.51), solubility (51.83%), bulk density (1.404 g/cm3), porosity (0.20), and diameter (6.44 μm) and the Hausner ratio (1.020). The thermal, crystallinity and surface morphology of the microencapsulated particles were also comprehensively studied using DSC, XRD, FTIR, and SEM. The storage stability of microencapsulated anthocyanin showed more stability at 4 °C than at 25 °C for 90 days. The microencapsulated particles also have an effect on the steady-shear rheology of the rice dough.