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Improvement of rheological properties of firm acid gels by skim milk heating is conserved after stirring

Published online by Cambridge University Press:  16 October 2003

P Cayot
Affiliation:
École nationale supérieure de biologie appliquée à la nutrition et à l'alimentation, Département d'ingénierie moléculaire et sensorielle de l'aliment, 1 esplanade Erasme, 21000 Dijon, France
J-F Fairise
Affiliation:
Arilait-Recherche, 34, rue de St Petersbourg, 75382 Paris, Cedex08, France
B Colas
Affiliation:
École nationale supérieure de biologie appliquée à la nutrition et à l'alimentation, Département d'ingénierie moléculaire et sensorielle de l'aliment, 1 esplanade Erasme, 21000 Dijon, France
D Lorient
Affiliation:
École nationale supérieure de biologie appliquée à la nutrition et à l'alimentation, Département d'ingénierie moléculaire et sensorielle de l'aliment, 1 esplanade Erasme, 21000 Dijon, France
G Brulé
Affiliation:
Institut national de la recherche agronomique, Laboratoire de recherche en technologie laitière, 65, rue de St Brieuc, 35042 Rennes, France

Abstract

The enhancement of the strength of set acid gels by heating milk was related to rheological parameters (water retention capacity, storage modulus) of corresponding stirred gels. To obtain accurate rheological data from stirred gel it was necessary to maintain a constant granulometry of gel particles and to recognize time after stirring as a contributing factor. Two hours after stirring, the gel exhibited a higher storage modulus when milk was heated above 80 °C. A measurement of viscosity of just-stirred yoghurt was sufficient to predict correctly the quality of a stirred gel analysed by viscoelastic measurements. Increased resstance to syneresis of just-stirred gels was related to higher viscosity. The quantity of β-lactoglobulin (β-lg) bound to casein micelles explains the improvement of these gel qualities. We have considered that the structure of the initial firm gel (mesostructure level) was conserved in fragments within the stirred gel. Consequently, the explanation given by various authors for the effect of heating milk on the properties of set gels can also be applied to stirred gels. The same mechanism, described in literature for structure formation of set gels from acidified milk is purposed to explain the role of heating milk on the recovery of gel structure after stirring. The β-lg association with casein micelles during heating favoured micelle connections during the acidification. It also favoured the association of gel fragments after stirring during the recovery in gel structure.

Type
Research Article
Copyright
© Proprietors of Journal of Dairy Research 2003

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