Storage stability and antioxidant activity of astaxanthin and beta-carotene as affected by the architecture of O/W emulsions of milk proteins

Abstract

Astaxanthin and β-carotene are among the potential anti-oxidant carotenoids with strong health promoting features. However, their sensitivity to light, heat and mechanical forces limit their application in food processing and storage conditions. The design of food matrix system, such as emulsions, that could prevent them from exposure to environmental factors will be utmost importance to slow down their degradation. In this study, O/W emulsion systems containing sunflower oil were prepared by applying ultrasound treatment and using different stabilizers (i.e. whey protein isolate (WPI) and sodium caseinate; NaCAS), co-surfactants (pectin and lecithin) while their performance against physical and chemical stability were investigated. The WPI– lecithin system produced emulsion droplets with Average diameter in the range of 560–2900 nm with a zeta-potential in the range of (−31) – (−34) mV, whereas the NaCAS – lecithin systems produced emulsion droplets with average diameter in the range of 230–240 nm and zeta potential of (−44) – (−48) mV. These values have a direct effect on the physical stability and chemical stability of the carotenoids in the emulsions. Astaxanthin was found to be more sensitive than β-carotene to ultrasound processing conditions. The designed emulsion systems slowed down the degradation of the carotenoids and maintained their DPPH scavenging properties during storage with astaxanthin loaded emulsions exhibiting better DPPH activity than β-carotene loaded emulsions. • Astaxanthin loaded emulsion exhibited better DPPH activity than β-carotene loaded emulsions. • β-carotene showed better resistance to ultrasound treatment conditions than astaxanthin. • Viscosity profile of the emulsions is highly correlated to the droplet size of emulsions. • Smaller size of emulsion droplets and higher zeta-potential offered better physical stability and protection of carotenoids. • Less acidic food environments are more favourable to the stability of β-carotene and Astaxanthin.