Effect of total solids content in feed emulsion on the physico-chemical properties and thermal stability of freeze-dried roselle extract

Abstract

Roselle anthocyanin has some potentials in the development of natural food colorants and as a source of antioxidant. Nevertheless, during processing or storage, some factors affects its stability and leads to the degradation. The purpose of this work is to analyze the effect of total solids content on the physico-chemical properties of freeze-dried roselle extract (FDRE) and compare the thermal stability with roselle extract under controlled temperature (80°C and 126°C) and period (0, 20, 40, 60, 80 min). Physico-chemical properties were done from the form of roselle extract, roselle pre-mix solution, and FDRE while thermal stability was done on roselle extract and FDRE following the first order of degradation kinetics. FDRE with 17%, 23%, and 28% total solids content (TSC) were prepared. Results proved that freeze-drying improved the physico-chemical properties and thermal stability of FDRE. Encapsulation efficiency represented that TSC of 28% was the best formulation among others and it affected the half-life of FDRE. At 80°C, TSC of 28% (277.26 min) had the half life 4 times longer than TSC 17% (67.96 min) while at 126°C, the half life of 28% TSC (154.03 min) was 2 times longer than 17% TSC (70.73 min).