Changes in markers of lipid oxidation and thermal treatment in feed-grade fats and oils.

Background: Oxidized feed lipids have been shown to have detrimental effects on food animal growth and metabolism. The present study aimed to measure classes of lipid oxidation products (LOP) in feed-grade oils at temperatures representing production and storage conditions.

Results: There were significant oil type × time interactions in the accumulation of primary and secondary LOP. At 22.5 °C, peroxide value (PV), a marker for the primary phase of lipid oxidation, increased most in fish oil (FO), followed by tallow (TL), soybean oil (SO), linseed oil (LO) and modified algae oil (MAO), whereas palm oil (PO) showed no appreciable increase in PV. Secondary LOP, such as p-anisidine value, hexanal, 2,4,-decadienal, polymerized triacylglycerols and total polar compounds, increased only in FO. At 45 °C, FO and SO produced both primary and secondary LOP, whereas MAO, PO and TL had slower rates of PV increase and no secondary LOP. At 90 °C and 180 °C, all oils except for FO accumulated both primary and secondary LOP.

Conclusions: Higher polyunsaturated fatty acid:saturated fatty acid oils and higher temperatures produced greater quantities of primary and secondary LOP. However, unrefined TL was more prone to oxidation at 22.5 °C than predicted, whereas LO was more stable than predicted, indicating that pro-oxidant and antioxidant compounds can markedly influence the rate of oxidation. Measuring both primary and secondary LOP will provide better information about the oxidative status of feed oils and provide better information about which classes of LOP are responsible for detrimental health effects in animals. Published 2020. This article is a U.S. Government work and is in the public domain in the USA.