Chemistry Reference
In-Depth Information
Table 11.3
Biochemical properties of main pectinases from Aspergillus niger for fruit processing.
◦
C
pH
range
Temp
Preferred
substrate
Enzyme
Mode of action
range
Functionality
30-45
◦
C Fully methyl-
esterified
oligogalactur-
onides
Endo-pectinlyase
Eliminative cleavage of
(1,4)-
4.0-6.0
Pectin viscosity
decrease
-
D
-galacturonan
methyl ester in
oligosaccharides with
4-deoxy-6-O-methyl-
α
α
-
D
-
galact-4-enuronosyl
groups at their
non-reducing ends
40-45
◦
C
Endo-
polygalacturonase
Random hydrolysis of
1,4-
3.5-6.0
α
-
D
-
galacturonosyl-
(1,4)-O-
Pectin viscosity
decrease
-
D
-galactosiduronic
linkages in pectate and
other galacturonans
hydrolysis of O-glycosyl
bond
α
-
D
-
galacturonate
+
α
H
2
O
30-60
◦
C (1,4-
Exo-
polygalacturonase
Catalyzing the
degradation of
D
-galacturonans by
terminal action pattern
3.0-5.2
-
D
-
galacturonide)
2
α
Release of
galacturonic
acid
+
H
2
O
40
◦
C
Pectinmethylesterase
Hydrolysis of carboxylic
ester
3.5-5.5
Methyl-esterfied
oligogalactur-
onides
Release of
methanol
+
H
2
O
50-60
◦
C 1,2-1,3-
Arabinofuranosidase
Hydrolysis of terminal
non-reducing
α
2.0-5.5
-
L
-
arabinosides
α
Improved access
to abn and agn
-
L
-arabinofuranoside
residues in
α
-
L
-arabinosides
40-45
◦
C1,5-
Endo-arabinase
Endohydrolysis of
1,5-
4.5-4.8
-
L
-
arabinan
α
Prevents araban
haze formation
in apple and
pear concentrate
-arabinofuranosidic
linkages in 1,5-arabinans
α
+
H
2
O
Commercial pectinases for the fruit juice industry come from selected strains of
A. niger
.
After strain growth in a defined culture medium, exo-cellular enzymes are purified and
concentrated.
Pectinases are defined and classified on the basis of their reaction to pectin and are grouped
into three main categories: lyases, hydrolases and esterases. The biochemical properties of
the main
A. niger
pectinases used in fruit processing are summarized in Table 11.3.
Figure 11.1 shows a schematic pectin composition.
13
Enzyme positioning on their sub-
strate named with gene codes is described in Table 11.2.
11.4
COMMERCIAL PECTINASES
11.4.1 Production
In juice processing it is not necessary to completely break down the fruit-flesh cell wall to
extract fruit juice. The main goal is to decrease the pectin's viscosity within the mash or
