Effect of pH and calcium chelation on cold gelling properties of highly concentrated-micellar casein concentrate

Highly Concentrated Micellar Casein Concentrate (HC-MCC) (17–23% casein content) gels upon cooling (<10 °C). We investigated the impact of pH and calcium chelation by adding tri-sodium citrate (TSC) on the cold gelling behavior of HC-MCC. Viscoelastic properties i.e., storage modulus (G’) and cold gelation temperature (CGT) were measured using three-stage multiwave oscillatory rheology. Samples withdrawn at different steps of gel formation were subjected to particle size, zeta potential, and transmission electron microscopy (TEM) analysis. It was clearly evident from TEM images and particle analysis that casein micelles swelled and retained their structural integrity at low temperature (5 °C). At natural pH (6.6), the gel strength of cold gels at 18.5% protein concentration was 3.12 kPa which was reduced to 1.49 kPa at pH 6.2 and increased to 15.8 kPa at pH 6.8. Alkalization and TSC addition resulted in an increase in particle size, and zeta potential favoring protein-water interactions. Gel strength and CGT both increased in response to TSC addition and alkalization, enabling formation of much stronger gel (G' = ∼15 kPa). Overall, this study serves as a foundation for future research for understanding the mechanism of gel formation and role of TSC and pH modification in improving cold gel formation characteristics. • The pH and calcium chelation affect the cold gelling behavior of HC-MCC. • Increased charge on casein micelles and solubilization of CCP leads to cold gelling. • At low temperature, the casein micelles swell and retain structural integrity of the gels. • Alkalization and calcium chelation improve cold gelling behavior of the HC-MCC.