THE INFLUENCE OF ELECTROLYTES ON THE SOLUTION AND PRECIPITATION OF CASEIN AND GELATIN

Area of Science:

• Colloid Science
• Physical Chemistry
• Protein Chemistry

Background:

• Colloids are classified as hydrophilic or hydrophobic based on electrolyte precipitation ease.
• Hydrophobic colloids precipitate at low electrolyte concentrations, following Hardy's rule.
• Hydrophilic colloids require high electrolyte concentrations for precipitation, with no clear ion charge relationship.

Purpose of the Study:

• Investigate electrolyte influence on Na caseinate (hydrophilic) and casein chloride (hydrophobic) solubility.
• Determine the forces governing dissolution in both colloid types.
• Clarify the role of Donnan equilibrium and particle swelling in colloid stability and precipitation.

Main Methods:

• Comparative solubility studies of solid Na caseinate and casein chloride in the presence of electrolytes.
• Analysis of dissolution mechanisms, focusing on Donnan equilibrium and particle swelling.
• Examination of electrolyte concentration effects on colloid stability and precipitation.

Main Results:

• Hydrophobic casein chloride dissolution is driven by swelling, regulated by Donnan equilibrium.
• Hydrophilic Na caseinate dissolution is attributed to residual valency forces, independent of Donnan equilibrium or swelling.
• Donnan equilibrium explains the stability of hydrophobic colloids and their precipitation by electrolytes, validating Hardy's rule for casein chloride.

Conclusions:

• Distinct mechanisms govern the dissolution of hydrophilic and hydrophobic colloids.
• Donnan equilibrium is crucial for hydrophobic colloid stability and electrolyte-induced precipitation.
• Further research is needed to elucidate the specific mechanisms of hydrophilic colloid salting out by different salts.