INVESTIGADORES
ZORRILLA Susana
congresos y reuniones científicas
Título:
Soft sphere behavior of casein micelles in concentrated milk suspensions
Autor/es:
OLIVARES, ML; BERLI, CLA; ZORRILLA, SE
Lugar:
New Orleans
Reunión:
Congreso; 2014 IFT Annual Meeting; 2014
Institución organizadora:
Institute of Food Technologists
Resumen:
Native casein micelles (CM) are colloidal particles formed via self-assembly of four casein
proteins and calcium phosphate. Even if the structure and composition of the CM
are now reasonably known, little has been done in understanding how these particles interact each other. Several authors showed that
dispersions of CM can be closely described by the so-called hard sphere model.
However, at higher packing fractions, the deformability of CM plays an
important role in the viscous behavior. Therefore, the aim of the present work
is to predict the rheological behavior of CM dispersions considered as soft
sphere particles. For this analysis, a simple
structure for CM composed of a spherical core with a brush of k-casein
was considered. A rheological model that
allows obtaining an explicit relationship between viscosity and shear stress
for non-Newtonian behavior of concentrated soft sphere suspensions was used. Experimental
viscosity curves were used to obtain the parameters of the viscosity model. The
effective maximum packing fractions and corresponding
to the shear stress limits and ,
respectively were obtained. The ratio grows almost
linearly as the core volume fraction increases and
reaches the limit value of 1 when 0.5 - 0.6. This
behavior agrees with the packing fraction of CM at the critical overlap concentration,
0.51. However, the ratio as function of shows a lower
slope and it does not reach the limit value of 1. This behavior may be
explained taking into account that CM behave as soft spheres and start to
deform and align along the flow direction at high shear rates. In addition, the
effective radius of CM may decrease as a consequence of hydrodynamic forces on
the k-casein layer. This study
has important implications for predicting the behavior of concentrated CM
suspensions in industrial operations such as membrane filtration,
evaporation, and drying.