Physical Chemistry of Foods
other organic solvents. The presence of other polymers may lead to phase separation (Section 6.5.2), which might be interpreted ...
is illustrated in Figure 7.14c. Here Line 1 indicates a relation that would be observed for a single pure protein of limited sol ...
Questions The globular proteinb-lactoglobulin generally is a mixture of two genetic variants, A and B. One difference is that A ...
shielded from the solvent due to association (it occurs as a dimer).b-casein is a disordered protein, having many hydrophobic re ...
elongated structures of mostly not very hydrophobic peptide chains; and (c) disordered, which structure somewhat resembles a ran ...
temperatures (mostly 50–80 8 C). Several complications can cause more complicated denaturation kinetics. Solubility. The solubil ...
A monograph on denaturation is S. Lapanje. Physicochemical Aspects of Protein Denaturation. John Wiley, New York, 1978. Kinetics ...
8 Water Relations The water content of foods varies widely, and several properties of foods greatly depend on water content. Thi ...
dependent food properties (such as its stability) than gravimetric water content, in the first place because several constituent ...
Dissociationof the solute. For NaCl,msshould be replaced by mNaþmCl, assuming complete dissociation. The broken line in Figure ...
net solvent–solute interaction, and q ¼12, the approximate value for sucrose in water. It is seen that the correction is somewha ...
from the Gibbs–Duhem relation [e.g., Eq. (2.13)], assuming interactions (i.e., net attraction or repulsion) between different so ...
Question 1 In what direction will the water activity of a liquid food change (higher, lower, or virtually unaltered) if the foll ...
Question 2 Calculate the water activity of a 25%(w/w) solution of glucose in water, assuming ideal behavior. What would be the e ...
with moist air can thus adsorb water. The amount adsorbed increases with increasing relative humidityðawÞof the air. Note that t ...
relations predominantly depend on food composition, and the basic factors governing them are given in Section 8.1. Figure 8.3c s ...
axis in graphs like those in Figure 8.3 does not represent the water activity of the food, at least at lowaw. In an actual food ...
i.e., about particle size—andt0.5¼time needed to halve a difference in concentration over a distancex^0 ), we obtain for water t ...
evaporation of water, which is 43 kJ?mol^1 at 40 8 C. Difficulty of removal of the last bit of water is thus not due to strong ...
inaw, a larger specific surface area of the material, and a higher diffusion coefficient of water in the material. If water upta ...
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