Chemistry Reference
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Table 1 Characterization of the casein micelle coverage as a function of the
interaction parameters: F
R
free, C
R
coating, P
R
patches. Free
(F) implies there is no whey protein particle (or very few) bound to the
surface. This occurs for a repulsive surface (A
o
0), or one of low
binding probability (p
{
1). For a high binding probability, and a not
too repulsive surface, a more-or-less homogeneous coating (C) is
formed. A special situation arises when a low binding probability is
combined with high attraction, for which the whey proteins form a
patchy cover (P) of the casein micelle
Parameter p
sl
10
5
10
4
10
3
10
2
10
1
A
sl
0
1
5
F
F
F
F
F
F
C
0
F
F
C
C
C
C
C
5
F
P
C
C
C
C
C
10
F
P
C
C
C
C
C
25
F
P
C
C
C
C
C
protein components, respectively. For these large-scale simulations we use
slightly different parameter values from those indicated above. High pH
corresponds to A
sl
¼
5 and p
sl
¼
10
3
(the lower binding probability gives
less coating); medium pH corresponds to A
sl
¼
5 and p
sl
¼
10
4
; and low pH
corresponds to A
sl
¼
25 and p
sl
¼
10
5
, the same as above. In Table 1 these
parameter values can be seen to lead to free micelles, coated micelles, and
patchy coatings, respectively. The other parameters are the same. In particular,
the large particles have only a repulsive Hookean overlap interaction.
The difference between the three sets of conditions in the pre-heating phase is
most obvious if we consider the number of bonds between the large particles
and the small ones (Figure 7). As a pair of particles can only form a single
bond, the plotted number is also the number of whey protein particles directly
bound to the casein surface. For the high pH system the number at the end of
the simulation is of the order of 100, implying that only about 2% of the whey
proteins are bound to the casein. In the medium pH system the number is
substantially larger, but still only
20% are actually bound to the casein
micelles, and so the average surface area covered is
B
15%. The patchy coating
at low pH has only 7% of the whey proteins actually bound.
B
18.4 The Gelation Phase
The second stage is the gelation phase. In the heat-treatment phase, we chose to
distinguish three sets of values of the interaction parameters, corresponding to
high, medium, and low pH. For comparison, we added a fourth case in which
the heat-treatment phase is omitted, i.e., with no complexation, but with
reactive whey proteins. During the gelation phase, the interaction parameters
are assumed to be the same for all four cases. Other differences from the
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