Biomedical Engineering Reference
In-Depth Information
200
160
120
80
40
addition of immobilized
invertase
0
0
2
4
6
8
10
12
14
16
18
20
time [h]
Fig.18.
Enzymatic hydolysis of sucrose following isomerization of glucose to fructose
4.6
Monitoring in Food Technology
In several European countries and the USA,the sterilization of milk is perfor-
med by addition of0.1% H
2
O
2
as a preservative.Catalase is an ingredient ofmilk
and decomposes H
2
O
2
. However, Novo Nordisk, Baegsvard, supplies catalase
especially for this procedure, and Boehringer Mannheim GmbH, Mannheim,
developed sensors to control remains of H
2
O
2
.The treatment of milk with H
2
O
2
prevents “cooking flavour”which is often obtained after pasteurisation processes.
Recently,Akertek and Tarhan (1995) showed that H
2
O
2
-sterilization has no nega-
tive effect on nutrients such as amino acids,proteins,vitamins,sugars or fats.
The ET is suitable for on-line monitoring of the raw milk sterilization pro-
cess.Here,immobilized catalase is inserted into the ET,raw milk samples with
H
2
O
2
are automatically diluted within a FIA-system and continuously analyzed.
Figure 19 shows on-line data of a H
2
O
2
decomposition experiment.After addi-
tion of 0.1% H
2
O
2
to raw milk, the ET signal increases tremendously whereas
addition ofcatalase obviously causes H
2
O
2
decomposition.Thus,raw milk's own
catalase seems to have a too low activity.
Aspartame monitoring represents a second interesting task for the ET.Immo-
bilized
-chymotrypsin hydrolyzes the artificial sweetener under release ofpro-
tons which are easily detected via a tris/HCl-buffer due to its high protonation
enthalpy.The immobilized enzyme unfortunately causes an unspecific conver-
sion. However, the procedure might be interesting for monitoring aspartame
during its industrial production within the Tosoh-process.
a
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