Water Binding of Food Constituents As, Determined by Nmr, Freezing, Sorption and Dehydration

The water binding properties of some common food constituents were determined by water sorption, dehydration, freezing and NMR methods. The sorption isotherms of sodium alginate, pectin, corn starch, casein and cellulose were obtained and the heats of adsorption and monolayer values were calculated. The unfreezable water contents of these five materials were determined and the values corresponded to the equilibrium moisture contents at a water activity of about 0.90. The bound water capacities of 14 food materials were determined using wide‐line NMR. These values correlated closely with the tertiary moisture contents determined by a drying rate study and the equilibrium moisture contents at 100% relative humidity. The different NMR properties of free and bound water were discussed in terms of nuclear relaxation times and molecular mobilities.