Oxidative and nutrient stability of a standard rodent spaceflight diet during long-term storage

The National Aeronautics and Space Administration's standard spaceflight diet for rodents is the nutrient-upgraded rodent food bar (NuRFB). The shelf life of the NuRFB needs to be determined in order to avoid malnutrition of rodents and confounding of research results resulting from nutritional deficiency. The authors compared the oxidative and nutrient stability of NuRFBs stored at either ambient temperature (26 degrees C) or at refrigeration temperature (4 degrees C) for use in long-term rodent feeding experiments. After 0, 3, 6, 9 and 12 months (mo) of storage, lipid oxidation, fatty acid composition and amounts of specific vitamins and amino acids in NuRFBs were analyzed. No oxidative rancidity developed in NuRFBs stored at 4 degrees C for up to 12 mo, but NuRFBs stored at 26 degrees C for 6 mo developed oxidative rancidity and had reduced amounts of gamma-linolenic acid (18:3n-6). Despite loss of vitamin E, vitamin A and thiamin after storage at 26 degrees C for 12 mo, vitamin levels in NuRFBs remained at or above the levels recommended for optimal rodent health. The amino acid profile of NuRFBs was unaffected by storage at 4 degrees C or 26 degrees C for 12 mo. The results suggest that NuRFBs stored at 4 degrees C for up to 12 mo and NuRFBs stored at 26 degrees C for up to 6 mo provide suitable nutrition for rodents in long-term experiments.