Model mixtures evidence the respective roles of whey protein particles and casein micelles during acid gelation
2014
Andoyo, Robi | Guyomarc'H, Fanny | Cauty, Chantal | Famelart, Marie-Hélène | Science et Technologie du Lait et de l'Oeuf (STLO) ; Institut National de la Recherche Agronomique (INRA)-AGROCAMPUS OUEST | Directorate General of Higher Education (DGHE) of the Ministry of Education and Culture Republic of Indonesia, under the grant of DGHE scholarship overseas program.
In acidified milk, heat-induced whey protein aggregates and casein micelle particles assemble to form asoft gel. The present study was set to evaluate the respective roles of whey protein aggregates (WPIA)and native casein micelles (NMC) during acid gelation by means of changing their ratio in model systems.NMC and WPIA were dispersed in milk permeate at different weight ratios ranging from 0% to 100% NMCfor a total protein concentration of w45 g kg 1. Acidification was performed at 35 C by addition ofglucono-d-lactone to achieve the same final pH of 4.5 in 6 h. Acid-induced gelation of these systems wasfollowed using small deformation rheology followed by large deformation test and whey retentionmeasurement at pH 4.5, while their microstructure was investigated microscopically. The results showedthat higher content in WPIA promoted faster gelation and led to more elastic gels with smaller pore sizeand increased whey retention. The effects were particularly dramatic up to w10% w/w WPIA, where theaggregates were about equimolar to the casein micelles and covered w8% of the micellar surface. Theresults were discussed in terms of the physical interactions between two populations of colloids ofdifferent abilities for acid gelation. It seemed likely that a preferred interaction exists between the caseinmicelles and the aggregates, and directs the structural and mechanical properties of the acid gel.
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