Colloidal gels from proteins and peptides - Physical Gels from Biological and Synthetic Polymers - page 267

(a)

(b)

(c)

(d)

Schematic of the stages envisaged for enzymatic coagulation of milk, starting from the initial
mixture of casein micelles and enzyme (a) and proceeding through proteolysis (b), initial
aggregation into small clusters (c) and attainment of the gel point at percolation (d). Adapted from
Horne and Banks ( 2004 ) © 2004 Elsevier.

Figure 9.6

of chymosin. Niki et al. used the method of Hooydonk and Oliemann to estimate GMP
from

-casein in casein micelles by rennet and to monitor the reaction of chymosin, and
the liberated GMP as a function of time (Ekstrand et al., 1978 ; McGann et al., 1980 ; Niki
et al., 1994a , 1994b ).
The gel time for small micelles was shorter than that for large micelles, in good
agreement with previous

κ

finding (Ekstrand and Larsson-Raznikiewicz, 1980 ). The
gelation time was found to be a decreasing function of temperature. The

nal
value of G 0 was proportional to the square of concentration, and showed a
maximum as a function of temperature. It is suggested that while hydrogen
bonding is not negligible in the gelation of casein micelles, this event is governed
mainly by hydrophobic interactions. Smaller micelles form a more solid-like gel
than larger micelles.