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Thermodynamic incompatibility and complex formation in pectin/caseinate mixtures
Camila F Rediguieri1, Osvaldo de Freitas, M Paul Lettinga
1Department of Pharmaceutical Sciences, University of São Paulo (FCFRP-USP), Avenida do Café s/n, Ribeirão Preto, SP, Brazil.
Biomacromolecules
|November 13, 2007
Summary
The instability of pectin/caseinate mixtures depends on pH. At higher pH, thermodynamic incompatibility causes phase separation, while lower pH leads to complexation and microparticle formation.
Area of Science:
- Food science
- Biochemistry
- Physical chemistry
Background:
- Polysaccharide/protein mixtures can exhibit instability due to thermodynamic incompatibility or complexation.
- Understanding these mechanisms is crucial for controlling mixture properties.
Purpose of the Study:
- To investigate the dominant instability mechanism in pectin/caseinate mixtures.
- To determine the effects of temperature, pH, and biopolymer concentration on phase separation.
Main Methods:
- Studied pectin/caseinate mixtures under varying temperature, pH, and concentration conditions.
- Observed phase separation phenomena, including spinodal decomposition and microparticle formation.
Main Results:
- At pH > 6, thermodynamic incompatibility caused spinodal decomposition and water-in-water emulsions.
- Lowering pH below 6 resulted in pectin/caseinate complexation and formation of stable microparticles.
- Increased pectin concentration or decreased temperature retarded demixing by increasing viscosity.
Conclusions:
- The pH is a critical factor determining the instability mechanism in pectin/caseinate mixtures.
- Thermodynamic incompatibility dominates at higher pH, while complexation prevails at lower pH.
- The resulting microparticles are stable and insensitive to salt addition.
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