Food Biochemistry and Food Processing

1 Food Biochemistry—An Introduction 7

of these enzymatic reactions. This table also lists
some enzymes and reaction products of organic acids
present in very small amounts in milk. However, they
are important flavor components (e.g., propionate,
butyrate, acetaldehyde, diacetyl, and acetoine).

REMOVAL OFGLUCOSE INEGGPOWDER
PRODUCTION

Glucose is present in very small quantities in egg
albumen and egg yolk. However, in the production
of dehydrated egg products, this small amount of
glucose can undergo nonenzymatic reactions that
lower the quality of the final products. This problem
can be overcome by the glucose oxidase–catalase
system. Glucose oxidase converts glucose to glu-
conic acid and hydrogen peroxide. The hydrogen
peroxide is then decomposed into water and oxygen

by the catalase. Application of this process is used

almost exclusively for whole egg and other yolk-

containing products. However, for dehydrated egg

albumen, bacterial fermentation is applied to re-

move the glucose. Application of yeast fermentation

to remove glucose is also possible. The exact pro-

cesses of glucose removal in egg products are the

proprietary information of individual processors

(Hill 1986).

PRODUCTION OFSTARCHSUGARS ANDSYRUPS

The hydrolysis of starch by means of enzymes (
-

and - amylases) and/or acid to produce glucose

(dextrose) and maltose syrups has been practiced for

many decades. Application of these biochemical

reactions resulted in the availability of various

starch (glucose and maltose) syrups, maltodextrins,

Table 1.1.Starch Degradation during Cereal Grain Germination

Enzyme Reaction

-amylase (EC 3.2.1.1) Starch →glucose
maltose
maltotriose

-limited
dextrins
linear maltosaccharides
Hexokinase (EC 2.7.1.1) D-hexose (glucose)
ATP →D-hexose (glucose)-6-
phosphate
ADP

-glucosidase (maltase, EC 3.2.1.20) Hydrolysis of terminal, nonreducing 1,4-linked
-D-glucose
residues with release of
-D-glucose
Oligo-1,6 glucosidase (limited dextrinase,
-limited dextrin →linear maltosaccharides
isomaltase, sucrase isomerase,
EC 3.2.1.10)
-amylase (EC 3.2.1.2) Linear maltosaccharides →Maltose
Phosphorylase (EC 2.4.1.1) Linear maltosaccharides
phosphate →
-D-glucose-
1-phosphate
Phosphoglucomutase (EC 5.4.2.2)
-D-glucose-1-phosphate →
-D-glucose-6-phosphate
Glucosephosphate isomerase (EC 5.3.1.9) D-glucose-6-phosphate →D-fructose-6-phosphate
UTP-glucose 1-phosphate uridyl (UDP- UTP

-D-glucose-1-phosphate →UDP-glucose

glucose pyrophosphorylase, Glucose- pyrophosphate transferase
1-phosphate uridyltransferase,
EC 2.7.7.9)
Sucrose phosphate synthetase UDP-glucose
D-fructose-6-phosphate →sucrose
(EC 2.4.1.14) phosphate
UDP
Sugar phosphatase (EC 3.1.3.23) Sugar phosphate (fructose-6-phosphate) →sugar
(fructose)
inorganic phosphate
Sucrose phosphatase (EC 3.1.3.24) Sucrose-6-F-phosphate →sucrose
inorganic phosphate
Sucrose synthetase (EC 2.4.1.13) NDP-glucose
D-fructose →sucrose
NDP
-fructose-furanosidase (invertase, Sucrose →glucose
fructose
succharase, EC 3.2.1.26)
Sources:Duffus 1987, Kruger and Lineback 1987, Kruger et al. 1987, Eskin 1990, Hoseney 1994, IUBMB-NC web-
site (www.iubmb.org).