Protein-stabilized oil-in-water emulsions and low-fat dairy stirred gels
2009
Bongard, Sébastien | Meynier, Anne | Riaublanc, Alain | Genot, Claude | Unité de recherche sur les Biopolymères, Interactions Assemblages (BIA) ; Institut National de la Recherche Agronomique (INRA)
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Show more [+] Less [-]English. The evolution of the oil-water interface was investigated throughout the preparation of stirred acid gels, which were models of stirred yoghurts. Stock emulsions were prepared (200 g.kg-1) and diluted to the final values of 15 g.kg-1 or 5 g.kg-1 by a solution of milk proteins. Gels were obtained by addition of glucono-delta-lactone and stirred. Evolution of the protein load and composition of the interface was investigated at 10,25 and 43°C. The protein load at the oil-water interface (mg.m-2) was similar regardless of the nature and level of fat, and the liquid versus gel state of the continuous phase. It was reduced upon storage ar 10°C, but tended to increase at higher temperatures. The caseins / whey proteins ratio (Cas/WP) was higher at the interface of fresh emulsions (fat content, 200 g.kg-1) than in skimmed milk. It decreased in low-fat matrices stored at 10°C, becoming generally not significantly different from that of skimmed milk. At the interface of stirred gels, it also decreased significantly with the temperature of storage. Re-organization of interfacial casein micelles and secondary adsorption of WP were involved. The protein load and composition at the interface of the final products could not be simply extrapolated from that of the original concentrated emulsions.
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