Figure 11.4 A plot of the logarithm of the aqueous stability of p lactoglobulin versus pH at two different ionic strengths, 0.001 and 0.01 mol kg_1. When the protein is charged at pH values below and above pH 5.3, solubility increases from its lowest point at the isoelectric point. Increased ionic strength shifts the isoelectric point to lower pH values, around 5.2. See also Fig. 11.6.

(NH4)2SO4, with a decrease in solubility occurring at higher ionic strengths - a salting-out effect. Several effects are responsible: (i) the preferential interaction of salts with bulk water, and (ii) the effect of the salts on the surface tension of water, which is related to the energy of cavity formation. The degree to

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