Models aggregates flocculation

The mechanism of protein haze formation in wines is not fully understood. Slow denaturation of wine proteins is thought to lead to protein aggregation, flocculation into a hazy suspension and, finally, formation of visual precipitates. The importance of non-proteinaceous factors in white wine protein haze formation such as proan-thocyanidins (Koch and Sajak 1959 Waters et al. 1995a Yokotsuka et al. 1991) have been suspected for some time. Other factors such as polysaccharides, alcohol levels and pH have also been implicated (Mesquita et al. 2001 Siebert et al. 1996a). It has been observed that grape protein added to model wine does not precipitate or produce haze when heated, whereas visually obvious hazes occur when the same protein is added to a commercial wine (Pocock 2006). 

Other general trends that are described correctly by the model [42] include an increasing r (relative) with particle aggregation (flocculation) and the onset of solid-like behavior (the existence of a yield stress ) in some dispersions at low shear rates. 

Figure 2 (a) Model of flocculation according to the Smolu-chowski scheme (b) coalescence in an aggregate of A particles to become an aggregate of i particles, with a rate constant 1 < i < k. (From Ref. 39.)... 

By use of Eq. (84) we allow for a spheroidal shape of the floes, as expressed through the parameters Ap 3d, f and 3K, f In this model the flocculated aggregates are characterized by the packing density of the droplets in the floe and a shape factor. 

With respect to Equation 5.37, the aggregates flocculation model allows thus, to consider that the low strain modulus of a CB filler compounds... 

Comparing the aggregate flocculation model (Equation 5.46) with the Guth and Gold equation data used Np(D)=200 particles, d=30nm, D=200 nmandfl=2 nm, G(0)=1 MPa,... 

This review indicates that good solvent conditions (in terms of either x or 0) result in a positive value for AGR. This is what would be expected from a model that assumes that the first encounter between particles with adsorbed layers is dominated by the polymers. Conversely, in a poor solvent AGR is negative and amounts to a contribution to the attraction between the core particles as far as flocculation is concerned. Under these conditions the polymer itself is at the threshold of phase separation. Van der Waals attraction between the core particles further promotes aggregation, but it is possible that coagulation could be induced in a poor solvent even if the medium decreases the effective Hamaker constant to zero. 

See Chapter V of R. Jullien and R. Botet, Aggregation and Fractal Aggregates, World Scientific, Singapore, 1987, for a description of cluster-cluster flocculation processes in the context of computer models. 

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