Effect of endoxylanases, endoglucanases and their combination on wheat flour bread quality
Date
2009-03
Authors
Roets, Carien
Journal Title
Journal ISSN
Volume Title
Publisher
Stellenbosch : University of Stellenbosch
Abstract
Endoxylanases are known to improve dough stability, oven spring, loaf volume, crumb structure
and shelf life. The use of endoglucanases (cellulases) usually results in increased bread loaf volume,
bread score and reduced crumb firmness. Even though bakeries use ‘pure’ enzymes in their
formulations, they are supplied with an enzyme mixture which can contain up to five different
enzymes. These mixtures often also include an emulsifier and ascorbic acid. To compare the ability
of endoxylanase and endoglucanase to improve bread quality characteristics, a commercial
endoxylanase (from Aspergillus niger) and endoglucanase (from Trichoderma reseei) were
evaluated together with a pure endoxylanase and endoglucanase (both from Trichoderma sp).
Baking trials were conducted on small (100 g) as well as commercial (700 g) scale. Quality
characteristics evaluated included dough quality, bread weight, bread height, bread volume, softness
of crumb, bread slice characteristics and overall crumb texture. All the results were compared to a
control. From the results of the small-scale baking trials both the pure and commercial
endoxylanases significantly (P<0.05) improved bread height and softness of crumb, with the pure
endoxylanase also increasing slice brightness. Both the pure and commercial endoglucanases
significantly (P<0.05) increased softness of the crumb and slice brightness. When the enzymes were
evaluated in combination, only an increase in bread height was observed for some of the
combinations.
From the results of the baking trials conducted on commercial scale, the loaf height was
significantly (P<0.05) increased by the pure endoxylanase and the pure endoglucanase, while the
bread volume was significantly (P<0.05) increased by all the enzymes being tested. Enzyme
combinations resulted only in a significant (P<0.05) increase in bread volume. The texture of the
bread crumb was significantly (P<0.05) influenced by the commercial endoxylanase, the pure
endoxylanase, the pure endoglucanase as well as two of the enzyme combinations, resulting in a
more open and coarse crumb texture. Slice brightness was significantly (P<0.05) decreased by the
commercial endoxylanase, the pure endoxylanase, the pure endoglucanase as well as the two
enzyme combinations. Both endoxylanases and endoglucanases can therefore be used to improve
bread quality characteristics such as bread height and/or volume, slice brightness and softness of
crumb. However, using pure enzymes specific characteristics can be targeted. This would become
more feasible if pure or single component enzymes become more readily available and cost
effective to use.
Apart from testing the effect of the enzymes on bread quality characteristics using small-scale
baking trials, it was shown in this study that testing of enzymes could also be efficiently conducted
on commercial scale. In the latter the enzymes were being tested using commercial white bread flour as well as a leaner formulation. The leaner formulation allowed for the effect of the enzymes
to be observed more prominently. The benefit of the evaluation on commercial scale was that the
effect of the enzymes was tested in a process similar to that used in industry.
Description
Thesis (Msc Food Sc (Food Science))--University of Stellenbosch, 2009.
Keywords
Endoglucanase, Bread quality, Dissertations -- Food science, Theses -- Food science