Complex coacervation in gelatin/sodium caseinate mixtures

• In gelatin/NaCN mixtures complex coacervation occur.
• Gelatin/NaCN mass ratio determines if formed complexes are soluble or insoluble.
• Neutral insoluble complex is always formed at gelatin:NaCN mass ratio 2:1.
• Interactions have a significant influence on rheological properties of gelatin gels.

Gelatin is a protein widely used in food, pharmaceutical and cosmetic products as an emulsifier, peptizer, thickener, and binder. Polypeptide structure of gelatin molecule facilitates its interactions with other oppositely charged ingredients often present in such products. Sodium caseinate (NaCN) due to its excellent functional and nutritional properties, is also very often used as a hydrophilic emulsifier in a wide range of dispersed systems together with other proteins, like gelatin. Since both proteins are polyelectrolytes, different type of interactions in such systems may occur. In the present study, turbidimetric, viscosimetric, surface tension, zeta potential and rheological measurements were performed in order to investigate the interactions in the mixtures of those two proteins. All these measurements showed presence of interaction between gelatin and NaCN that resulted in insoluble complex coacervate formation at certain proteins ratio.

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