Chemistry Reference
In-Depth Information
100
Alcalase
capacity
Alcalase
stability
Protamex
capacity
Protamex
stability
80
60
40
20
0
0
5
10
15
20
25
Degree of hydrolysis (%)
Fig. 13.13
Foaming properties of whey protein concentrate and the hydrolyzate produced by Alcalalse
and Protamex (adapted from Ref. [34]).
The DH is very low, approximately 0.5% for optimum functionality. The enzyme used was
M. miehei
protease, which is also well known as microbial rennet for cheese production.
High DH negatively influences foaming properties. This has been documented by
Severin and Xia,
34
who tested whey protein hydrolyzates (Fig. 13.13).
They also found that there are big variations in the foaming properties, dependent upon
the type of enzyme used. They tested Alcalase and Protamex and found the properties of
hydrolyzates made with Protamex to be best. However, hydrolysis by these enzymes resulted
in a significant decrease in the stability of the foam starting at a DH of 5%. Unfortunately, they
did not have any data in the DH range of 0-5% where optimal performance of hydrolyzates
can be expected, according to the results shown in Fig. 13.12.
In another study showing the difference between using Alcalase and Neutrase, it was
shown that a hydrolyzate made with Alcalase had a 12-fold improvement in foam expansion,
whereas with Neutrase only four times better results were obtained compared with un-
hydrolyzed protein. In both cases, the maximum foam expansion occurred at DH 3-4%.
40
There is no consensus about the DH range for optimum foaming capacity. Don
et al.
41
have found that soya protein hydrolyzed with a
Bacillus subtilis
protease had maximum
foaming capacity at about 10% DH, whereas with
Aspergillus oryzae
protease an increased
foaming expansion up to DH of 20% was obtained.
Some illustrative results were produced by Perea
et al.
,
42
showing the foaming capacity
and foaming stability of an Alcalase-hydrolyzed whey protein concentrate in the DH range of
0-22% (Fig. 13.14). It appears that the foaming capacity is high when the foaming stability
is relatively low and vice versa.
Va n d e r Ve n
et al.
43
investigated the foaming properties of whey and casein hydrolyzates
produced by 11 different commercial proteases. All casein hydrolyzates formed high initial
foam volume but had lower stability than intact casein. Best stability was achieved at relatively
low DH. For whey protein, the foaming properties differed with molecular weight distribution
of the peptides. A large fraction of peptides with a molecular weight range of 3-5 kD had
the best foam formation. The stability of foam produced with whey protein hydrolyzates was
also lower than intact protein.
13.5.6 Gelling
The classic utilization of proteolytic gelling in foods is cheese production. By specific
proteolysis, the
-casein in milk is hydrolyzed at the peptide bond Phe
105
-Met
106,
causing
the charge of the casein micelle to change, thus enabling the gelation. One of the reaction
products is casein macro peptide (CMP), which is released into the whey. Whey has been
κ
