Food Chemistry

2.7 Enzyme Utilization in the Food Industry 149

2.7.2 IndividualEnzymes

2.7.2.1 Oxidoreductases

Broader applications for the processing industry,
besides the familiar use of glucose oxidase, are
found primarily for catalase and lipoxygenase,
among the many enzymes of this group. A num-
ber of oxidoreductases have been suggested or
are in the experimental stage of utilization, par-
ticularly for aroma improvement (examples un-
der 2.7.2.1.4 and 2.7.2.1.5).

2.7.2.1.1 GlucoseOxidase........................................

The enzyme produced by fungi such as As-
pergillus nigerandPenicillium notatumcatalyzes
glucose oxidation by consuming oxygen from
the air. Hence, it is used for the removal of
either glucose or oxygen (Table 2.20). The H 2 O 2
formed in the reaction is occasionally used as an
oxidizing agent (cf. 10.1.2.7.2), but it is usually
degraded by catalase.
Removal of glucose during the production of egg
powder using glucose oxidase (cf. 11.4.3) pre-
vents theMaillardreaction responsible for dis-
coloration of the product and deterioration of its
whippability. Similar use of glucose oxidase for
some meat and protein products would enhance
the golden-yellow color rather than the brown
color of potato chips or French fries which is ob-
tained in the presence of excess glucose.
Removal of oxygen from a sealed package system
results in suppression of fat oxidation and oxida-
tive degradation of natural pigments. For exam-
ple, the color change of crabs and shrimp from
pink to yellow is hindered by dipping them into
a glucose oxidase/catalase solution. The shelf life
of citrus fruit juices, beer and wine can be pro-
longed with such enzyme combinations since the
oxidative reactions which lead to aroma deterio-
ration are retarded.

2.7.2.1.2 Catalase

The enzyme isolated from microorganisms is im-
portant as an auxiliary enzyme for the decompo-
sition of H 2 O 2 :

(2.108)

Hydrogen peroxide is a by-product in the treat-

ment of food with glucose oxidase. It is added to

food in some specific canning procedures. An ex-

ample is the pasteurization of milk with H 2 O 2 ,

which is important when the thermal process is

shut down by technical problems. Milk thus sta-

bilized is also suitable for cheesemaking since the

sensitive casein system is spared from heat dam-

age. The excess H 2 O 2 is then eliminated by cata-

lase.

2.7.2.1.3 Lipoxygenase

The properties of this enzyme are described under

section 3.7.2.2 and its utilization in the bleach-

ing of flour and the improvement of the rheo-

logical properties of dough is covered under sec-

tion 15.4.1.4.3.

2.7.2.1.4 Aldehyde Dehydrogenase

During soya processing, volatile degradation

compounds (hexanal, etc.) with a “bean-like”

aroma defect are formed because of the enzy-

matic oxidation of unsaturated fatty acids. These

defects can be eliminated by the enzymatic

oxidation of the resultant aldehydes to carboxylic

acids. Since the flavor threshold values of

these acids are high, the acids generated do not

interfere with the aroma improvement process.

(2.109)

Of the various aldehyde dehydrogenases, the

enzyme from beef liver mitochondria has

a particularly high affinity for n-hexanal (Ta-

ble 2.21). Hence its utilization in the production

of soya milk is recommended.

2.7.2.1.5 Butanediol Dehydrogenase

Diacetyl formed during the fermentation of beer

can be a cause of a flavor defect. The enzyme

fromAerobacter aerogenes, for example, is able

to correct this defect by reducing the diketone to

the flavorless 2,3-butanediol:

(2.110)