Effect of Dehulling Treatment on the Oxidative Stability of Cold-Pressed Low Erucic Acid Rapeseed Oil

This study compared the oxidative stability of cold-pressed rapeseed oil (CPRO) and dehulled cold-pressed rapeseed oil (DCPRO) in the dark at 60 °C and monitored the evolution of minor constituents (tocopherols, phytosterols, phenolics). The results showed that dehulling significantly influenced the oxidative stability of the oils, the DCPRO was more easily oxidized. During the autoxidation, the peroxide value (PV) and anisidine value (p-AV) of the DCPRO ranged from 2.38 to 95.97 mequiv O₂ kg⁻¹ and from 1.20 to 30.75, whereas those of the CPRO ranged from 3.80 to 46.17 mequiv O₂ kg⁻¹and from 2.69 to 14.87, respectively. Dehulling affected the contents and the rates of decrease of tocopherols and phytosterols of the cold-pressed oils, and the rates of decrease of tocopherols and phytosterols of the CPRO were lower than those of the DCPRO (10% less, on average). The rancimat induction periods (IPs) were positively correlated with the concentrations of the total tocopherols (For DCPRO, R ² = 0.9622, For CPRO, R ² = 0.8334). The total phenolics contents as determined by spectrophotometry first increased and then decreased. Tocopherols and phytosterols had a greater effect on oxidative stability of the rapeseed oils during the first 30 days, and phenolics had a greater effect in the 30–40 day period.