Effect of ethanol on the microstructure and rheological properties of whey proteins: Acid-induced cold gelation

The microstructure and mechanical properties of ethanol-denatured, acid-induced whey protein (WPI) cold-set gels have been monitored by confocal laser scanning microscopy and rheology. As the ethanol concentration increased, the porosity of the gels progressively decreased, with gels prepared at ethanol concentrations of 50 and 70 g/100 g lacking microscopically visible pores. Large aggregates were observed at ethanol concentrations of 70 g/100 g immediately after alcohol addition. A sharp increase in storage modulus was noted at ethanol concentrations between 30 and 50 g/100 g, while the gel strength at 50 g/100 g, was up to three times higher compared to that of heat-denatured gels. In general, the ethanol-denatured whey protein cold-set gels were prone to phase separation. Ethanol-denatured cold-set whey protein gels exhibited mechanical and microstructural properties that may offer alternative means of structuring protein-enriched food formulations and designing novel food products.