Protein aggregates modulate the texture of emulsified and acidified acid milk gels
Résumé
Acid milk gels with fat (3.5 or 10%) or without fat containing 0.2–1% of whey proteins (WP) or 0.2–1.5% ofprotein aggregates (fractal aggregates, microgels and mixed casein/WP aggregates with an 80/20 ratio) wereinvestigated. The fat-containing systems were homogenized and the systems were preheated (90 °C, 11 min) andacidified to a pH of 4.6 by adding glucono-delta-lactone. The protein composition of the fat droplet interface wascharacterized by SDS-PAGE and the textural and rheological properties, microstructure, and whey separation ofacid networks were determined. WP and fractal aggregates showed the best ability to improve the texturalproperties and microstructure of all acid milk gels and reduce whey separation. Increasing the concentrations inmicrogels and mixed aggregates did not lead to an increase in gel firmness or generate a strong impact on theprotein network, but a high concentration in mixed aggregates could reduce whey separation. The fat dropletinterface was made almost exclusively of caseins, even if the fractal aggregates could also be adsorbed when theinterfacial surface was increased either through fat content or through an increase in homogenization pressure.Adding proteins changes the textural properties of the acid gels in all the systems, mainly due to their role in thecontinuous phase.
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