340: Impact of Protein Concentration on Cold Gelling Behavior of Reconstituted Micellar Casein Concentrates

Introduction

Micellar casein concentrate can form thermoreversible cold gels at concentration at higher concentrations (>15% solids). This property can be disadvantageous in high protein beverage formulation. Most of the studies on cold gelling phenomenon have been conducted on liquid version of MCC before drying. However, high protein beverages mostly utilize dried form of MCC. Therefore, we studied the impact of concentration on cold gelling property of reconstituted MCC.

Methods

Micellar Casein Concentrates (MCC) powder was reconstituted in water to 5-23% protein concentration. Cold gelling temperature (CGT) and strength of cold were determined using three step protocol on the MCR-302 Rheometer with concentric cylinder geometry conducting Multiwave oscillation test. Three steps included, holding at 60°C/ 1 hour, ramping down from 60-5°C/ 1 hour and curing the gel at 5°C/ 12 hours. The evolution of casein micelle size over cooling from 60 to 5°C was determined using dynamic laser light scattering device, Litesizer 500.

Results

Cold gels were not formed below 15% protein concentration. However, with increasing protein concentration from 15% to 20%, CGT increased from 8.9°C to 35°C indicating ease of cold gel formation at higher concentration. On the other hand, final storage modulus (G’) increased from 87 Pa to 3082 Pa with increasing protein concentration from 15-20%. At 23% protein concentration reconstituted powder exhibited gel like characteristics at even 60°C with absence of CGT, indicating jamming transition. Particle size increased from 100 nm to 180 nm during cooling MCC solution from 60 to 5°C with a sharp increase around 30°C, suggesting swelling of micellar structures. During curing stage, G’ increased by twice after storing gel for 12 hours at 5°C indicating further strengthening of the cold gel. Frequency dependence of G’ decreased with increasing protein concentration, suggesting a stronger network.

Significance

Cold gel formation is a common problem in high protein milk beverages. Findings from this work will help devise some strategies to avoid this defect in ready to mix beverages.

Authors: Jasper Shekin J, Prateek Sharma*