Chemistry Reference
In-Depth Information
900
525
600
350
300
175
0
0
0
5
10
15
20
25
Degree of hydrolysis (%)
Fig. 13.14
The effect of the degree of hydrolysis on foaming properties of hydrolyzed whey protein
concentrate made by Alcalase treatment. Foaming capacity
, foaming stability
. (Reprinted from Ref.
[42], Copyright (1993), with permission from Elsevier.)
found to have properties that can be utilized by isolating the CMP and use it in functional
food products. Instead of producing cheese from the curd it can be used for production of
rennet casein. In this case, the curd is heated which contracts the gel and releases the whey,
followed by drying of the casein.
The utilization of proteases has also been suggested for the coagulation of soya
protein.
44-46
In section 13.5.5, the use of a Glu-specific enzyme was mentioned which can cause
viscosity increase and eventually gelling of whey protein solutions. This section describes
gelling by a number of proteases in surprising conditions. Trypsin, papain, Pronase and a
protease from
Streptomyces griseus
all caused gelling of whey protein. The DH for gelling
was 27.1% for trypsin, 23.1% for papain, 28.2% for Pronase and 15.6% for the
S. griseus
protease.
47
To
et al.
48
found that pepsin did actually improve the gel strength of whey protein
concentrate but at lower DH.
A special term - plastein reaction - has been used for describing the gelling/aggregation
taking place when a protein hydrolyzate/peptide mixture is incubated with a protease. Even
though the plastein formation is hardly utilized in the production of protein ingredients, it
is of interest since it can develop during the production of protein hydrolyzates. The most
important parameters for plastein formation are type and size of peptides, concentration of
peptides and pH of the reaction mixture. Generally, the DH of the protein hydrolyzate must
be high to promote the plastein formation. Casein hydrolyzate with a molecular weight of
380-800 Dalton was the best substrate for plastein formation.
49
Plastein formation generally takes place at a pH value different from that of the optimum
for hydrolysis. Adler-Nissen
8
tested eight different proteases and showed that all but one had
a pH optimum for plastein formation 2-3 pH units away from the optimum for hydrolysis.
Only papain had the same pH optimum for hydrolysis and plastein formation.
It has been suggested by Fujimaki
et al.
50
and Lalasdis and Sjoberg
51
that the plastein
reaction can be used to reduce the bitterness of protein hydrolyzates. Several researchers have
suggested improving the nutritive value of a protein hydrolyzate by incorporating essential
