Effect of Roselle (Hibuscus sabdariffa L.) extract on physical properties and lipid oxidation stability of model extra virgin olive oil emulsions

Abstract

This research studied the effect of Roselle (Hibiscus sabdariffa. L) extract on the physical properties and lipid oxidation stability of extra virgin olive oil (EVOO) emulsions. The methods used to test the physical properties were droplet size distribution, microstructure observation, flow behavior analysis, viscosity, pH, color and centrifugation assay. While, peroxide value (PV) and p-Anisidine value (AV) were used to investigate lipid oxidation stability under accelerated oxidation at 60 C for 10 days and the total oxidation was calculated as Totox value. 0.02 % Roselle extract emulsion showed lower polydispersity (Span = 1.76) and more uniform droplet size compared with BHTE and NAE through droplet size distribution and microstructure observation. There are flocculation and coalescence happen for all freshly prepared emulsions. Viscosity of 0.02% Roselle extract (0.02 RE) emulsions at 10 s- ° showed the lowest viscosity (0.089 mPa s) measured using a controlled stress rheometer while the viscosity of 0.02 RE was the highest (--4 Pa s) when it was tested at 200 s- 1 using viscometer. pH of the emulsions were in the increasing order for 0.02 RE< 0.01 RE <NAE< BHTE. 0.02 RE emulsion showed the lowest lightness and yellowness which represented by L * and b* values with 86.38 and 13.91, respectively.