Food Biochemistry and Food Processing

8 Part I: Principles

maltose, and glucose for the food, pharmaceutical,
and other industries. In the 1950s, researchers dis-
covered that some xylose isomerase (D-xylose-keto-
isomerase, EC 5.3.1.5) preparations possessed the
ability to convert D-glucose to D-fructose. In the
early 1970s, researchers succeeded in developing
the immobilized enzyme technology for various ap-
plications. Because of the more intense sweetness of
fructose as compared to glucose, selected xylose
isomerase was successfully applied to this new tech-
nology with the production of high fructose syrup
(called high fructose corn syrup in the United States).
High fructose syrups have since replaced most of the

glucose syrups in the soft drink industry. This is

another example of the successful application of

biochemical reactions in the food industry.

BIOCHEMICAL CHANGES OF

PROTEINS AND AMINO ACIDS IN

FOODS

PROTEOLYSIS INANIMALTISSUES

Animal tissues have similar structures even though

there are slight differences between mammalian land

animal tissues and aquatic (fish and shellfish) animal

Table 1.2.Degradation of Complex Carbohydrates

Enzyme Reaction

Cellulose degradation during seed germinationa
Cellulase (EC 3.2.1.4) Endohydrolysis of 1,4--glucosidic linkages in cellulose and
cereal -D-glucans
Glucan 1,4--glucosidase Hydrolysis of 1,4 linkages in 1,4--D-glucan so as to remove
(Exo-1,4--glucosidase, EC 3.2.1.74) successive glucose units
Cellulose 1,4--cellubiosidase Hydrolysis of 1,4--D-glucosidic linkages in cellulose and
(EC3.2.1.91) cellotetraose releasing cellubiose from the nonreducing
ends of the chains
b-galactosan degradationa
-galactosidase (EC 3.21.1.23) -(1→4)-linked galactan →D-galactose
b-glucan degradationb
Glucan endo-1,6--glucosidase Random hydrolysis of 1,6 linkages in 1,6--D-glucans
(EC 3.2.1.75)
Glucan endo-1,4--glucosidase Hydrolysis of 1,4 linkages in 1,4--D-glucans so as to
(EC 3.2.1.74) remove successive glucose units
Glucan endo-1,3--D-glucanase Successive hydrolysis of -D-glucose units from the
(EC 3.2.1.58) nonreducing ends of 1,3--D-glucans, releasing -glucose
Glucan 1,3--glucosidase 1,3--D-glucans →
-D-glucose
(EC 3.2.1.39)
Pectin degradationb
Polygalacturonase (EC 3.2.1.15) Random hydrolysis of 1,4-
-D-galactosiduronic linkages in
pectate and other galacturonans
Galacturan 1,4-
-galacturonidase (1,4-
-D-galacturoniside)n
H 2 O →(1,4-
-D-
[Exopolygalacturonase, poly galacturoniside)n-1
D-galacturonate
(galacturonate) hydrolase,
EC 3.2.1.67)
Pectate lyase (pectate transeliminase, Eliminative cleavage of pectate to give oligosaccharides with
EC 4.2.2.2) 4-deoxy-
-D-galact-4-enuronosyl groups at their
nonreducing ends
Pectin lyase (EC 4.2.2.10) Eliminative cleavage of pectin to give oligosaccharides with
terminal 4-deoxy-6-methyl-
-D-galact-4-enduronosyl
groups
Sources:aDuffus 1987, Kruger and Lineback 1987, Kruger et al. 1987, Smith 1999.
bEskin 1990, IUBMB-NC website (www.iubmb.org).