Accelerated Solvent Extraction Improves Efficiency of Lipid Removal from Dry Pet Food While Limiting Lipid Oxidation

Accelerated solvent extraction (ASE) was evaluated for extracting lipids from baked and extruded dry pet foods to determine factors controlling extraction efficiency and effects on lipid oxidation. Hydroperoxide decomposition and new lipid oxidation were minimal at 40 °C but increased at higher extraction temperatures without increasing yields. Maximum extraction required grinding samples to 250 µm particles, presence of polar solvents [chloroform, chloroform/methanol 2:1 (v/v) mixed, hexane/methanol 2:1 (v/v)], and a minimum of 20 min total static extraction time in repeat extraction cycles. Hexane and methanol injected into extraction cells simultaneously but separately was able to nearly duplicate extractions of chloroform/methanol, providing an option for replacing toxic chlorinated hydrocarbon solvents in ASE. However, lipid oxidation was higher in hexane. Yields were quantitative in baked biscuits but lower in extruded kibbles due to more dense, complex molecular structures. ASE extraction yields of 40 min or less were comparable to manual extraction yields of 24–48 h, with lower oxidation. Overall, one or two ASE extraction cycles with static times less than 20 min appeared to provide adequate lipid yields that accurately reflect lipid composition while inducing minimal modification when lipid oxidation products are the analytical endpoint.