Effect of three different preservative systems on the stability of extruded dog food subjected to ambient and high temperature storage.

Three different preservative treatments were applied to extruded dog food. After processing the dog foods were placed in bags and stored for 16 wk at 48.8 degrees C for 12 mo at 22.2 degrees C. The preservative treatments were as follows: 1) ethoxyquin and butylated hydroxyanisole (EX/BHA), 2) mixed tocopherols (TC/TC) and 3) ascorbyl palmitate and mixed tocopherols (ATL/TC). There were no significant differences among treatments for thiobarbituric acid values for either the high or ambient temperature tests, whereas peroxide value (PV) showed significant treatment and storage effects. For products stored at 22.2 degrees C, PV increased linearly from week 4 to week 16 in both the TC/TC and ATL/TC preservative treatments and was significantly higher than the PV for EX/BHA. In the ambient temperature test, the PV was also higher for the TC/TC and the ATL/TC treatments compared to the EX/BHA treatment after 5 and 12 mo of storage. Results of the sensory evaluations were closely associated with PV. In both the high and ambient temperature tests the dogs consumed more of the foods with the lowest PV when given a two-bowl choice. Using PV and sensory tests as criteria, we concluded that the ATL/TC and TC/TC preserved dog foods deteriorated during storage compared to the EX/BHA preserved food in both the high and ambient temperature tests.