Effect of endoxylanases, endoglucanases and their combination on wheat flour bread quality
Thesis (Msc Food Sc (Food Science))--University of Stellenbosch, 2009.
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.