Water hydration capacity values

Table IV. Water hydration capacity values of various protein...

The protein fraction showed low nitrogen solubility and rather low water hydration and oil absorption values relative to those of the proteinates but oil emulsification was quite high. Refined legume fiber had a water hydration capacity of over 20 g/g product. 

Functional property tests were conducted in duplicate. AACC (21) methods were used for the determination of water hydration capacity (Method 88-04) and nitrogen solubility index (NSI) (Method 46-23). Oil absorption capacity was measured by the procedures of Lin et al. (22) and oil emulsification by a modification (22) of the Inklaar and Fortuin (23) method. Pasting characteristics of 12.0% (w/v, db) slurries of the flours and processed products were determined on a Brabender Visco/Amylograph (Method 22-10). The slurries were heated from 30 to 95°C before cooling to 50°C to obtain the cold paste viscosity value. Gelation experiments were conducted by heating 15% (w/v db) slurries in sealed stainless steel containers to 90°C for 45 min in a water bath C3). 

Figure 3. The heat capacity (Cp) for the water intercalated between the layers of kaolinite in the 10A hydrate. Standard values for ice and liquid water are also shown. The heat capacity of the intercalated water was measured using the procedure described in Reference 2.

Both hydrocolloids and emulsifiers increase the water-binding capacity in the mix (increased % of hydrogen atoms with low T2 and decreased T2 values). A synergistic effect is observed when both ingredients are present. From studies described earlier in this chapter, the effect of hydrocolloids is assumed to be due to simple water binding and increased thickness of protein layers around the fat globules, whereas the effect of emulsifiers may be due to the increased hydration of interfacially bound protein as well as increased hydration of polar groups of emulsifier at the oil-water interface. 

Recently, we have measured the partial molar heat capacity Cp of hydrated samples of methylcellulose and elastin at temperatures ranging from 110°K to 330 K (37). For both, just as for collagen, at any temperature, the partial molar heat capacity of water appears to be independent of water content. Its values is equal to that of ice from 110°K to 150°K, where it starts to increase over that of ice and then increases virtually linearly with temperature to values close to that of liquid water at room temperature. Schematically, the results are given in... 

As seen in Table 2.2, the values of P and Va/b are far away from the spherical form and are accurate to form rod-like, as pectin [159], alginate [160]. The hydration value accounts for the high water adsorption capacity for this polysaccharide and its great industrial potential application in highly viscous and thick solutions. The of Tara gum is between the values specified by Wu et al. [161]. 

The fact that the water molecules forming the hydration sheath have limited mobility, i.e. that the solution is to certain degree ordered, results in lower values of the ionic entropies. In special cases, the ionic entropy can be measured (e.g. from the dependence of the standard potential on the temperature for electrodes of the second kind). Otherwise, the heat of solution is the measurable quantity. Knowledge of the lattice energy then permits calculation of the heat of hydration. For a saturated solution, the heat of solution is equal to the product of the temperature and the entropy of solution, from which the entropy of the salt in the solution can be found. However, the absolute value of the entropy of the crystal must be obtained from the dependence of its thermal capacity on the temperature down to very low temperatures. The value of the entropy of the salt can then yield the overall hydration number. It is, however, difficult to separate the contributions of the cation and of the anion. 

Applying the established temperature dependence of A, Cp to the substances listed in Tables II and III, one can find that the enthalpy of the transfer of all these substances from the gaseous phase to water decreases to zero within the temperature range 100-180°C (Fig. 10). As is evident, when one linearly extrapolates A%H values determined at 25°C, using the usual assumption that Ag Cp is temperature-independent, one finds a lower value of the temperature TH(g w) at which the hydration enthalpy is zero (see the last column in Table II). It is clear, however, that these values, obtained by linear extrapolation, i.e., assuming constant heat capacity increment, have only a fictitious meaning. Nevertheless, in all cases one can conclude that the heat of solvation becomes zero at an elevated temperature in the range of 410 40 K. 

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