Impact of storage conditions on protein oxidation of rendered by-product meals

Rendered products used in animal feed and pet food undergo extreme temperatures during manufacturing and may be stored up to 2 yr. No information is available on protein oxidation in these products. The objective of this study was to determine the extent to which typical antioxidant inclusion at different storage conditions may limit protein oxidation in typical rendered protein meals. Two experiments were conducted on 14 rendered products stored at either 45 degrees C for 7 or 14 d, or at 20 degrees C for 3 or 6 mo to determine the extent to which time, temperature, and antioxidants affect protein oxidation. Results from this study show that fish meal and chicken blood meal are susceptible to protein oxidation during storage at 45 degrees C (P = 0.05; 0.03) as well as during storage at 20 degrees C (P = 0.01; 0.04). Natural antioxidants were effective at limiting carbonyl formation in fish meal during short-term storage at 45 degrees C, whereas ethoxyquin was effective at limiting the extent of protein oxidation in fish meal stored long term at 20 degrees C.