EQUILIBRIUM MOISTURE CHARACTERISTICS OF FREEZE‐DRIED BEEF COMPONENTS

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Abstract
SUMMARY –The equilibrium moisture content isotherms of beef components and fractions were measured and analyzed. Measurements were conducted in an electrobalance system which allows continuous measurement of sample weight change during the experiment. Equilibrium moisture content isotherms were measured for water soluble and water insoluble fractions, actomyosin, connective tissue (collagen) and sarcoplasmic fraction along with raw and precooked freeze‐dried beef. The measurements were conducted at 52° and 70°F. In general, the moisture adsorption by product components was very low at low water activities when compared to the freeze‐dried product. Actomyosin adsorbed only a small amount of moisture until a water activity greater than 0.6 was exceeded. Although the influence of temperature on the magnitude of water activity was as expected, the shapes of desorption isotherms were abnormal when compared to desorption isotherms for the precooked freeze‐dried beef. A comparison of desorption isotherms for raw and precooked freeze‐dried beef revealed a similar difference. An attempt to predict product isotherms from knowledge of component isotherms and weight fractions of components revealed that predictions were significantly lower than experimental values.