INVESTIGADORES
BERLI Claudio Luis Alberto
congresos y reuniones científicas
Título:
Soft sphere behavior of casein micelles in concentrated milk suspensions
Autor/es:
MARÍA L. OLIVARES, CLAUDIO L. A. BERLI, SUSANA E. ZORRILLA
Lugar:
New Orleans
Reunión:
Congreso; IFT Annual Meeting & Food Expo (IFT 2014); 2014
Institución organizadora:
Institute of Food Technologies
Resumen:
Native casein micelles (CM) can be considered as
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 colloids
interact with 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. The effective maximum packing fractions and corresponding to the shear stress limits and , respectively were
obtained from this model. Experimental viscosity curves were used to obtain the
parameters of the viscosity model. 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. The results obtained are very promising to predict the
behavior of concentrated CM suspensions in industrial operations such as
membrane filtration, evaporation, and drying.