Abstract

Phytosterol esters with anti-cholesterol potential have been synthesized and fortified into various emulsion-based foods. However, phytosterol esters as one of the lipid species are prone to oxidation. Here, oxidations of oil-in-water (o/w) emulsions containing β-sitosteryl oleate and native β-sitosterol were evaluated during storage at 65 °C for 35 days. Changes in chemical indices, namely the hydroperoxide value, thiobarbituric acid reactive substances, p-anisidine value, and 7-keto substances, differed depending on the sterol structure. Losses of β-sitosteryl oleate and β-sitosterol in the o/w emulsion kinetically fitted the first order. A faster rate of loss was observed in β-sitosteryl oleate (k = 0.0244 day⁻¹/R² = 0.8838) when compared to native β-sitosterol (k = 0.0085 day⁻¹/R² = 0.9819). The molecular structure and crystallinity can be the main parameter affecting the loss of phytosterol and its ester in the o/w emulsion during storage.