The gradual disaggregation of casein micelles improves their emulsifying capacities and decreases the stability of dairy emulsions. - Université de Rennes Accéder directement au contenu
Poster De Conférence Année : 2016

The gradual disaggregation of casein micelles improves their emulsifying capacities and decreases the stability of dairy emulsions.

Résumé

Casein micelles are highly aggregated colloidal particles of 150 to 200 nm diameter constituted of 4 casein molecules (αs1, αs2, β, κ) and minerals (mainly calcium phosphate). Physico-chemical changes alter the casein-mineral interactions and consequently modify their organization. These modifications provide possibilities for the development of new casein aggregates with original structures that deliver novel functionalities. The objective of our work was to investigate the emulsifying and emulsion-stabilizing properties of gradually demineralized casein aggregates in model dairy emulsions. Sodium citrate, a calcium chelating salt, was used to remove calcium and inorganic phosphate from the casein micelle. 4 suspensions of differently demineralized casein aggregates were produced and physico-chemically characterized. 2 different types of milkfat-in-suspension (30:70) emulsions were then prepared to separately study the emulsifying and emulsion-stabilizing capacities of these casein aggregates. Results of atomic absorption spectrometry showed a progressive demineralization of the casein micelles with the increase in sodium citrate concentration (from 24 to 81% of calcium impoverishment). The characterization of the suspensions by asymmetrical flow field flow fractionation pointed out the presence, in every suspension, of 3 distinct populations of particles (micelle-like aggregates - Rh of 110 to 270 nm, smaller aggregates - Rh of 10 to 20 nm and casein monomers). Their respective proportions varied as a function of the amount of added tri sodium citrate. Indeed, the progressive demineralization of the large aggregates induced their dissociation and the release of small casein aggregates and monomers.The emulsions formed with the 4 different casein suspensions at a concentration of 1.20 g.L-1 became thinner in size with the increase in demineralization rate. This result showed an increase in emulsifying capacities for the small aggregates that were able to stabilize larger amounts of suspension/milkfat interface compared to the large ones. Interfacial studies demonstrated that each type of aggregates had similar surface activities and confirmed that the state of aggregation of the casein is the main factor that controlled their emulsifying capacities.Increasing the concentration of casein aggregates in suspensions to 20 g.L-1 enabled to produce 4 emulsions with identical droplet size. These emulsions were less stable against creaming and flocculation when the aggregate demineralization rate increased, but still resist to coalescence under our storage conditions (21 days at 50°C). The characterization of the interfacial casein layers indicated that their properties did not depend on the type of casein aggregates used to form the emulsions. The stability differences observed can therefore be attributed to the nature of the non-adsorbed casein aggregates.Our study revealed that modulating the mineral content of the casein micelles is an interesting tool to understand its role in the formation and the stabilization of emulsion. This strategy can and will be extended to the study of other techno-functionalities.
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Dates et versions

hal-01339540 , version 1 (29-06-2016)

Identifiants

  • HAL Id : hal-01339540 , version 1
  • PRODINRA : 358412

Citer

Fanny Lazzaro, Eric Beaucher, Christelle Lopez, Marie-Noelle Madec, A. Saint-Jalmes, et al.. The gradual disaggregation of casein micelles improves their emulsifying capacities and decreases the stability of dairy emulsions.. 13. International Hydrocolloids Conference (IHC), May 2016, Guelph, Canada. 2016. ⟨hal-01339540⟩
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