The impact of saponification on the stability of sterol oxidation products as related to alkalinity and time of reaction

The cold saponification is widely applied to analyze sterol oxidation products (SOPs), which are debated compounds due to their implications on human health. However, it may itself compromise analytical accuracy due to the formation of artefacts. Thus, a comprehensive understanding of the SOPs' behavior during cold saponification is pivotal. The present study investigated the impact of cold saponification conditions, including KOH concentrations (1, 2, 4 mol/L) and reaction times (2, 4, 18 h) on the stability of 7-ketocholesterol (7-KC), 7-ketositosterol (7-KSit), 7-ketocampesterol (7-KCamp), 7-ketostigmasterol (7-KSt), 7β-hydroxycholesterol (7β-OH) and 5β,6β-epoxycholesterol (5,6β-EP). Results showed that all 7-keto derivatives significantly degraded. In contrast, 5,6β-EP and 7β-OH exhibited a greater stability. The behavior of 7-keto derivatives and 5,6β-EP was also evaluated in medium-chain triglycerides (MCT) system, powdered milk and French fries. In MCT the residual content of 7-keto derivatives in model system was <23 %. On the other hand, in powdered milk, 4 mol/L KOH (18 h) decreased the presence of 7β-OH and 7-KC; while no significant differences ( p > 0.05) were found on the 5,6β-EP content. Again, in French fries lipid matter, a significant reduction of 50.37 %, 38.17 % and 42.92 % was noted for 7-KSit, 7-KCamp and 7-KSt, respectively. This study demonstrated that also cold saponification could influence the stability of SOPs, offering the experimental basis required to reevaluate and enhance existing analytical techniques.