Lipid source and kibble matrix determine oxidative stability and n-3 fatty acid loss in coated extruded dog food

Abstract Lipid oxidation is a key determinant of nutritional quality, palatability, and shelf life in extruded dog foods. This study evaluated how lipid source, kibble matrix, and antioxidant inclusion influence oxidation and shelf life of coated extruded dog kibble. Two kibble matrices (grain-inclusive and grain-free) were formulated to meet adult maintenance recommendations and externally coated at 10% (as-is) with 1 of 10 lipid sources [algae, fish, flax, camelina, canola, sunflower, coconut, black soldier fly larvae (BSFL) oil, chicken fat, duck fat] or left uncoated (control). Each coated treatment was produced with or without a natural antioxidant blend (tocopherols + rosemary extract; 200 ppm), then stored under ambient (22 °C, 50% RH; 15 mo) and accelerated conditions (37 °C, 40% RH; 3 mo). Oxidation was assessed via peroxide value (PV), hexanal, 2,4-decadienal, and tocopherols, and time to failure was defined as PV ≥ 5 mEq/kg or (hexanal + 2,4-decadienal) ≥ 25 ppm. Proximate, mineral, and fatty acid profiles were assessed during ambient storage. Under ambient storage, PV and aldehydes increased with time (P < 0.05), and oil source influenced oxidation markers and fatty acid losses (P ≤ 0.01). Oils rich in polyunsaturated fatty acids (PUFA; algae, flax, and camelina) had greater oxidation, more rapid tocopherol depletion, and shorter time to failure than more saturated lipid sources (coconut and poultry fats). Baseline double bond index (DBI) predicted oxidative failure (P < 0.0001). Mean eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) concentrations across treatments decreased by 98.7% and 77.9%, respectively, from 0 to 15 mo. Grain-inclusive kibble was associated with greater aldehyde accumulation (P < 0.05), greater antioxidant depletion (P < 0.0001), and shorter time to failure than grain-free kibble (P = 0.001). Antioxidant inclusion increased baseline tocopherol concentrations but did not consistently affect PV or secondary aldehyde concentrations or extend time to failure across oil types at the inclusion level used (P > 0.10). In the present study, lipid source was the dominant determinant of oxidative stability, with baseline DBI supporting degree of fatty acid unsaturation as an important contributor, alongside meaningful contributions from the kibble matrix. Effective preservation of long-chain n-3 PUFA requires formulation-specific stabilization strategies, beyond a uniform antioxidant solution, or alternative delivery approaches.