Effect of kappa carrageenan on acid-induced gelation of whey protein aggregates. Part II: Microstructure

Publication date: Available online 14 December 2019Source: Food HydrocolloidsAuthor(s): Dasong Liu, Peng Zhou, Taco NicolaiAbstractThe influence of κ-carrageenan (KC) was investigated on the microstructure of gels formed by acid-induced gelation of whey protein aggregates (WPA). In part I of this two-part series we discussed results obtained by potentiometric titration, rheology and turbidimetry. Here we report on the microstructure of both the proteins and the polysaccharides using confocal laser scanning microscopy with different fluorescent labels for each type of biopolymer. The effect of KC concentration at fixed net protein charge densities (α) and the effect of α at fixed KC concentrations were studied. It is shown that WPA starts to form microdomains and associates with KC at approximately the same α. Microstructures at steady state at different α were compared with those obtained at different times during in-situ acidification after addition of GDL. Significantly different microstructures were observed at elevated gelation temperatures. Fluorescence recovery after photobleaching measurements showed that a significant fraction of the KC chains associated with the proteins could still freely exchange even when the proteins were strongly positively charged. The observations of the microstructure are compared with those obtained with other experimental techniques that were reported in part I.Graphical abstract

Source: Food Hydrocolloids - December 16, 2019 Category: Food Science Source Type: research