Chemistry Reference
In-Depth Information
Table 6.8
Effects of
β
-mannanase and guar on the anti-staling properties of bread.
Dough
consistency
Improver
Xylanase
Mannanase
Guar
Freshness (4 days)
1
39.000
62
0
1
2
2
39.000
0
0.1%
2
3
3
39.000
62
0.1%
1
1
Galactoglucomannan is the major hemicellulolytic component of softwood. Two different
structures can be identified within this group of polysaccharides. Both consist of a
β
-1,4-
linked D-mannose backbone, which can be substituted by
α
-1,6-linked D-galactose. The
galactoglucomannan backbone also contains
-1,4-linked D-glucose residues. Water-soluble
galactoglucomannan has a higher galactose content than does water-insoluble galactogluco-
mannan and in addition contains acetyl residues attached to the main chain. Approximately,
20-30% of the backbone glucose and/or mannose residues are esterified with acetyl groups
at C-2 or C-3.
Mannanases are useful in several industrial processes, such as the extraction of vegetable
oil from leguminous seeds and the reduction of the viscosity of coffee extracts during manu-
facture of instant coffee. In the pulp and paper industry, mannanases can act synergistically
with xylanases as biological pre-bleaching agents for soft wood pulp, allowing a significant
reduction of environmental pollution compared with the use of chlorine-based chemical
agents. However, in spite of these potentially interesting applications, the widespread use of
mannanases is limited due to high production costs for the enzyme.
Mannanases are produced by microorganisms such as mould or yeast fungus as well as
Bacillus subtilis
,
Aeromonas
,
Enterococcus
,
Pseudomonas
and
Streptomyces
. Some higher
plants or animals can produce mannanase. Microorganisms used for production of the man-
nanase are usually
Trichoderma
or
Aspergillus
sp. fungal strains.
Industrial applications of mannanases in bread making have been described.
76, 206
β
The
use of a
-mannanase in a baking improver in the preparation of baked goods improves
the properties of dough and that of the final baked product. With regards to the dough,
the tolerance can be improved, but also the dough flexibility, dough stickiness and general
handling properties. With regards to the final baked product, mannanase retards staling and
improves crumb structure.
206
Interesting is that the addition of a mannanase together with
glucomannan and/or galactomannan such as guar of konjac gum, improves the properties of
the dough and the baked products even further. This is shown in Tables 6.8 and 6.9.
206
β
Table 6.9
Effect of specific enzymes on dough characteristics and shape.
Specific
volume with
Shape with
Dough
proofing time
proofing time
50
65
50
65
Improver
Consistency
Stability
KBrO3
1
−
6
4
100
100
Xylanase (Xyl.)
4
+
7
5
104
103
Xyl.
+
glucose oxidase
2
+
7
5
106
105
Xyl.
+
β
-mannanase
3
+
7
5
106
105
Xyl.
+
β
-mannanase
+
2
++
7
6
107
107
glucose oxidase
