Effects of high-temperature stages on the physicochemical properties and oxidation products formation of rapeseed oil with carnosic acid

With the extension of heat processing, the oxidation and formation of harmful substances in oils appeared. The effect of the high-temperature stages (180 °C, four stages I, II, III, and IV were divided according to the heating-up period) on the fatty acid profile, the thermal properties, the composition of total polar compounds, and the physicochemical properties of rapeseed oil (RSO) were investigated. As the heating processing, carnosic acid (CA) significantly reduces the peroxide value, p-anisidine value, trans-fatty acid, the action of alkyl radicals, and the formation of oxidized triglyceride monomers (Ox-TGM). The Tp of the RSO shifts towards the lower temperature, and the enthalpy exhibits a significant decrease in stages II, III, and IV. Stage II is the crucial period for the transformation of Ox-TGM into polymers. CA helps control the oxidation process of the oil. It is essential to maintain the quality and prolong the usage time of RSO. [Display omitted] •The fatty acid composition of rapeseed oil experiences the most intense changes in stage IV.•Carnosic acid can delay the formation of oxidized triglyceride monomers (Ox-TGM).•Ox-TGM serves as a crucial precursor for the formation of oil-oxidizing polymers.•Stage II is the crucial period for the formation of high-temperature oxidation polymers.•Carnosic acid can effectively limit the action of alkyl radicals in high-temperature stages