Soy isolates, soy concentrate, soy flour, and ovalbumin were analyzed for amounts of unfrozen water at different total moisture contents. Analysis was by differential scanning calorimetry to determine heats of fusion and integral heats of vaporization. Unfrozen water did increase with increased total water content. When plotted against total moisture (dry basis), the unfrozen water was a linear function of total water above a concentration of 1 g of water/g of solids, and ~10% of added water was unfrozen. Plots of integral heats of vaporization vs. total water gave peaks below the critical moisture content.Bound water can be defined as the water that remains unfrozen in samples held well below 0 °C (Fennema, 1977).

No abstract

Water 4 Molecular chemistry 4 Cooperative hydrogen bonding 5 Water structure 6 Bound water and water activity 17 Measurement of Bound Water 21 Nuclear magnetic resonance 21 Steady-state NMR 21 Pulsed NMR 27 Calorimetry 32 Calorimetric measurement of bound water 33 Dehydration 33 Occurrence of fusion 35 Measurement of freezable water 37 Dieletric measurements 42 Vaporization of Water 44 Heat of vaporization 44 Vaporization curves 46 Heat Capacity 48 Structured Water of Hydration 50 NMR evidence 50 Dielectric evidence 53 MATERIALS AND METHODS 54 Materials 54 Calorimetric standards 54 Soy protein products 54 Ovalbumin 55 iii Methods 55 Calorimetric measurements 55 Calibration 55 Bound water 56 Heat of vaporization 56 Water content 59 Sample preparation 59 Weights 62 RESULTS AND DISCUSSION 63 Bound Water 63 Initial results 63 Comparison with other bound water studies 63 Results of other calorimetric studies 66 Measurement of bound water in other protein systems 67 Comparison of bound and free water contents 72 Linear regression 85 Critical moisture contents 86 Methodological variables 88 Conflict with NMR data 89 Heat of Vaporization 97 Results 97 Analysis of results 105b Relationship to NMR data