The effect of adding salt on aggregation at other pH values has not yet been studied in much detail. Schmitt et al. (2007) found that the turbidity of a WPI dispersion (10 g L1) after 15 min heating at 85 C increased more quickly with increasing NaCl concentration if the pH was lowered between pH 7.0 and 6.0. It is reasonable to suppose that the effect of adding salt in this pH range is similar to that at pH 7, but that it occurs at lower salt concentrations when the pH is lower. The heterogeneity of gels formed at 100 g L1 b-lg also increased more rapidly with increasing NaCl concentration if the
pH was reduced in this range (Mehalebi et al., 2008a). Not much is known yet about the effect of the type of salt on
the aggregation. The aggregation process at pH 7.0 in 0.1 M CH3COONH4 is the same as in 0.1 M NaCl, but Cg is smaller in CH3COONH4 (∼7 g L1) than in NaCl (∼15 g L1), which suggests that CH3COONH4 screens electrostatic interaction more efficiently. A much bigger effect is found when CaCl2 is used. Baussay et al. (2004) mention that at pH 7.0 Cg is less than 1 g L1 in 1 mM CaCl2. Croguennec, O’Kennedy, et al. (2004) observed at this pH much faster depletion of native b-lg in 1 mM CaCl2 than in 15 mM NaCl. No oligomers and a smaller amount of non-native monomers were formed in the presence of CaCl2. Oligomers that were formed without salt aggregated rapidly when 1 mM CaCl2 was added. O’Kennedy and Mounsey (2009) observed in the pH range 5.0e7.0 that more proteins were denatured after 10 min at 78 C in 5 mM CaCl2 than in 100 mM NaCl.