Effect of water activity on lipid oxidation and protein solubility in freeze-dried beef during storage

Ground beef patties (15% fat) were freeze-dried to different a, endpoints and stored at 25degreesC or 49degreesC. Water activity, total moisture (%), lipid oxidation (TBARS@450nm), and protein solubility were evaluated. TBARS @450nm was favored at 49degreesC,but not at 25 degreesC except at high a(w) range (p < 0.05), whereas protein solubility was greater at 25 degreesC than 49degreesC (p < 0.05).TBARS@450nm values at 49degreesC were generally greatest at low a. range (p > 0.05). Protein solubility was lowest at medium a(w) at 49 degreesC (p < 0.05), while at 25 degreesC low a(w) protected protein solubility better than other low or high a(w) values.