Chemistry Reference
In-Depth Information
DH had a broad range of droplet size. The last group of hydrolyzates was characterized by a
relatively large droplet size but within this group there was a relationship between DH and
emulsion stability. Increasing DH resulted in decrease in emulsion stability.
The emulsifying properties of extensively hydrolyzed proteins are of importance in low
allergenic baby food products. An indication of the decrease in emulsifying properties at
very high DH in the range of 25-67% has been documented.
36
At these high DH values
minimal emulsifying properties were found. The practical implications of the inferior emul-
sifying properties are that baby food formulations and other nutritional products made with
extensively hydrolyzed proteins often require the addition of emulsifiers. The protein/peptide
part is not effectively keeping the emulsion stable as is often seen with native proteins. A
detailed discussion of the difference between whey protein and hydrolyzed whey protein has
been made by Tirok
et al.
37
who suggest use of lysolecithin to help stabilizing emulsions
with hydrolyzed whey protein. A good emulsion in food products promotes the uptake of the
nutrients besides giving a better appearance.
13.5.5 Foaming
The use of hydrolysis to improve the foaming properties has been suggested for making an
egg white substitute from soya protein.
38
It was proposed that soya protein isolate at DH of
3% made by Alcalase could be used (see Fig. 13.12).
From this figure it is evident that the type of raw material used for making hydrolyzates
is important. When using acid-precipitated soya protein, representing the typical production
process for soya isolate, there is a narrow maximum for foaming expansion/capacity.
If instead ultrafiltration-derived soya isolate is used, the foaming properties are quite
different and better.
In a process patented by Boyce
et al.
,
39
the use of a very specific protease is suggested
for the hydrolysis of soya protein isolate to produce a high-quality egg white substitute.
1600
1400
1200
1000
Ultrafiltered
Acid precipitation
800
600
400
200
0
0
2
4
6
8
10
Degree of hydrolysis (%)
Fig. 13.12
Whipping expansion of soya protein hydrolyzates produced by Alcalase and Neutrase
(adapted from Ref. [24]).
