Colloidal Behaviour of Casein Micelles with Concentration

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Colloidal Behaviour of Casein Micelles with Concentration

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dc.contributor.advisor Corredig, Milena
dc.contributor.author Krishnankutty Nair, Pulari
dc.date 2012-09-10
dc.date.accessioned 2012-09-14T14:29:30Z
dc.date.available 2012-09-14T14:29:30Z
dc.date.issued 2012-09-14
dc.identifier.uri http://hdl.handle.net/10214/3997
dc.description.abstract Structure function changes of casein micelles were studied as a function of concentration using a non invasive concentration method, osmotic stressing. A combination of serum analysis, light scattering and rheological measurements were used to characterize the physico-chemical properties of casein micelles. In heated and unheated milk, rheological studies indicated that casein micelles behave as hard spheres of similar volume fractions, if the viscosity changes in the serum phase and the particle particle interactions are taken into account. The differences in the distribution of the heat induced complexes between colloidal and soluble phase affected the colloidal properties of casein micelles. Above 70 g L-1 protein, the protein particles were no longer free diffusing. Re-dilution of the suspensions showed no irreversible aggregation. The data suggested that in the range of concentration studied casein micelles behave as hard spheres. Age gelation was also investigated on heated and unheated concentrated milk. In unheated concentrated milk proteolysis played an important role in imparting an increase in viscosity by causing aggregation of the casein micelles. On the other hand, in heated milk, there was a significant effect of the whey protein aggregates, which increased their interaction with the casein micelles over time. This effect, together with proteolysis caused age gelation in heated concentrated milk. The method of concentration used in this research, osmotic stressing, was then compared to ultrafiltration. It was demostrated that these two methods are not equivalent, as shear and mixing during ultrafiltration cause rearrangements to the casein micells. The differences were clearly demonstrated by adding soluble caseins to the milk before or after concentration. This project brings a better understanding on the effects of concentration on the structure-function of casein micelles and the interactions occurring in milk proteins during concentration. en_US
dc.language.iso en en_US
dc.subject Casein Micelles, Concentrated milk, Sodium Caseinate, Age gelation, Rheology, Colloidal Properties en_US
dc.title Colloidal Behaviour of Casein Micelles with Concentration en_US
dc.type Thesis en_US
dc.degree.programme Food Science en_US
dc.degree.name Doctor of Philosophy en_US
dc.degree.department Department of Food Science en_US


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