The Use of Xylanases from Different Microbial Origin in Bread Baking and Their Effects on Bread Qualities
Moayad H. Khataibeh
Effects of xylanases on bread quality were examined.
Enzymes used were endo-xylanase (EC 22.214.171.124) from different sources of
microorganisms. Baked loaves were assessed for Loaves volume, colour
and staling rate. Xylanases produced from rumen microorganisms M6 had
clearly positive effects on loaf volume of bread as well as anti-firming
potential. M3 (produced from Trichoderma longibrachiatum) improved
crumb softness. The use of xylanase for breadmaking lowered firmness of
bread crumb effectively compared with control loaf. It can be summarized
that xylanases had significant positive effects on bread characteristics.
In particular, they had advantage in retarding the staling rate of bread.
It is recommended that the optimum dosage of enzymes, method of application
in industrial scale especially with xylanase should be studied further
in order to gain the great advantages of enzyme addition in breadmaking.
The use of enzymes during the manufacture of baking products is a primitive
process. In fact, our ancestors already used these enzymes without their
being aware of them because flour naturally contains enzymes. During recent
decades, enzymes have been used on purpose and the application of enzymes
in the bakery has become widespread (Poldermans and Schoppink, 1999; Rani
et al., 2001; Gámbaro et al., 2006; Caballero et
Xylanase has been introduced recently as it can improve the handling
properties of dough, the ovenspring and the bread volume. Moreover, it
has the potential to retard staling thus increases the shelf life of the
bread (Hilhorst et al., 1999). Xylanases are enzymes that specifically
hydrolyze xylans which are the most widely occurring polysaccharides (Uhlig,
1998). In wheat flour, xylans are mainly present as arabinoxylans which
are the cell wall components. Arabinoxylans can be in both water-soluble
and water-insoluble forms. Water-soluble pentosans will hold water about
10 times of their weight in water (Mannie, 2000). In order to increase
the amount of water-soluble pentosans, xylanases are added to bread dough.
During the process of enzymatic hydrolysis, Xylanases can break glycosidic
linkages in arabinoxylans, leading to a smaller fragments of carbohydrates
and therefore water is released in the dough. As a consequence, the dough
becomes softer; the handling properties of dough, the ovenspring and the
bread volume are improved. It also increases the shelf life of bread (Hilhorst
et al., 1999).
Over recent years, the role of xylanases in breadmaking has been investigated
intensively (Hilhorst et al., 2002; Jiang et al., 2005;
Collins et al., 2006; De Schryver et al., 2007). Girhammar
(1993) reported that addition of xylanase increased loaf volume of standard
wheat flour breads significantly. The application of Aspergillus aculeatus
xylanase in bread and bakery products has been introduced by Qi-Si (1995).
The effects of purified endo-beta-xylanase on the structure and baking
characteristics of rye doughs have been investigated by Autio et al.
(1996). Red winter wheat flour, which was treated with beta-xylanase before
the addition to bread formula, resulted in slightly improved crumb grain
(Lin-Wang et al., 1998). Hilhorst et al. (1999) claimed
that the use of peroxidase in combination with xylanase improved the handling
properties of the doughs and the final baked product. The combination
of xylanase and lipase decreased fermentation time and increased dough
extensibility (Collar et al., 2000). There have been several studies
concerned with anti-staling potential of xylanases incorporated with other
enzymes such as amylase, lipase and protease (Martinez-Anaya et al.,
1998, 1999; Gil et al., 1998, 1999).
Hence, the main purpose of the present study was to investigate the effect
of xylanase from different sources on bread quality and bread staling.
MATERIALS AND METHODS
Materials: Super Bakers Flour (Goodman Fielder) (Moisture, 11.9%;
Protein, 11.7%; Ash, 0.66%), Lowan Instant Dry Yeast, Saxa Iodised Cooking
Salt, White Sugar (CSR), xylanases (EC126.96.36.199) (Megazyme International
Ireland Ltd.), they were identified as M1 (from Trichoderma viride,
205 U mg-1); M2 and M3 (from Trichoderma longibrachiatum,
64 and 132 U mg-1, respectively); M4 (from Aspergillus niger,
79.3 U mg-1); M5 (from Humicola insolens, 200 U mg-1)
and M6 (from rumen microorganism, 405 U mg-1), they were suspended
in 3.2M ammonium sulphate solution and kept under refrigerated temperature
Bread making formula: Four hundred and fifty grams strong breadmaking
flour, 9 g sugar, 8 g instant yeast, 7.5 g salt, 9 g vegetable oil and
283.5 mL water. The mixture was processed in an automatic breadmaker (Panasonic
SD-253, Matsushita Electric Ind. Co. Ltd., using a rapid cycle of 1 h
and 55 min. Test loaves were baked from each formula. Baked loaves were
allowed to cool for 1 h at 25 °C before storage and stored in sealed
polyethylene bags at room temperature for periods of up to 5 days, breads
were treated with 10 μL of the xylanase per dough.
Bread firmness: Bread firmness measurements were made with a Texture
Analyser (TA-XT2, Stable Micro Systems, England). Slices (25 mm thickness)
were compressed to 40% (6 mm) using a 35 mm diameter aluminium plunger
with a 5 kg load cell. The rate of compression was 1.7 mm sec-1.
The compression curves of the bread crumb (distance vs. force) were plotted
and the force readings (in Newton) at 25% compression were taken as a
measure of firmness in accordance with AACC method 74-09 (AACC, 2001).
Two slices were analyzed from each loaf.
Loaf volume: The values of bread loaf volume samples were determined
by the RACI standard procedure (RACI, 1995). For this, bread loaf volume
was estimated from the sum of two circumference values of the loaf. The
second measurement was taken perpendicular to the first. All measurements
were taken after 1 h of cooling at room temperature and the sum expressed
Colour measurement: The colour of bread was measured by the Minolta
Chroma Meter (CR-300). The results were recorded by the L*, a* and b*
values at three different points on crust and crumb of bread (RACI, 1995).
Assessment and scoring of baked loaves: This assessment was scored
out of a total of ten points. One meant the poorest and 10 the best. The
factors to be considered were overall symmetry, smoothness, stickiness,
uniformity of crumb cells, aroma and taste.
Data analysis: Experimental data were analyzed using analysis
of variance (ANOVA) (SPSS v.11, SPSS Inc., Chicago, IL), a value of (p<0.05)
was considered significant difference.
RESULTS AND DISCUSSION
In consideration of loaf volume, the control loaf without any of xylanases
was smaller than the other loaves Fig. 1. Loaf using
M6 (from rumen microorganism) clearly was the largest loaf with the highest
loaf volume. Loaf using M2 and M3 was also larger than control, M1 and
M3 in volume.
These findings confirm data that obtained with the other xylanases reported
(McCleary, 1986; Maat et al., 1992; Martinez-Anaya and Jimenez,
1997; Norma and Guillermo, 2003). Courtin et al. (1999) found the
use of endoxylanases impacted significantly on final loaf volume and Jiang
et al. (2005) who fond that the specific volume of bread was increase
30% by using xylanase.
Crumb firmness of control and treated loaves was measured and the results
are shown in Fig. 2. During the first day, loaves with
M1, M2 and M6 were significantly softer than the control loaves and other
loaves (p<0.05). Second and third day, the loaves treated by enzyme
had significantly lower firmness than the control loaf (p<0.05). After
that, the firmness of every loaf increased rapidly excluding the M3 loaf
which the firmness was stable from the second day to the third day.
Firmness of crumb is one of the most evident changes observed during
bread storage. The influence of xylanases on the process of bread staling
is still being debated. Information on this aspect is confusing possibly
because of the variety of xylanases exist (Jiang et al., 2005).
Some results indicated that added xylanases (or hemicellulases or pentosanases)
do not modify the crumb-firming rate, but decrease the initial crumb firmness,
possibly by increasing the loaf volume (Rouau et al., 1994). However,
the results in other studies show that the addition of xylanases can decrease
the staling rate of bread (Martinez-Anaya and Jimenez, 1997; Laurikainen
et al., 1998). It has also been reported that xylanases are among
different carbohydrases that exerted the greatest effect on the anti-staling
during bread storage (Haros et al., 2002).
|| The effect of xylanases on bread loaf volume
||The effect of addition xylanases on crumb firmness of
||The effect of addition xylanases on crust L* value of
All added xylanase retarded
the staling rate of breads in this study. The staling rate was retarded
possibly because of the breakdown of the polysaccharide network and the
presence of more hygroscopic oligosaccharides. Hence, xylanase possibly
induced retardation of the bread staling by reducing the initial crumb
firmness and the firming process during storage (Jiang et al.,
||The effect of addition xylanases on crumb L* value of
||The effect of addition xylanases on crust b* value of
Colour is an important sensory attribute in bread. One criterion consumers
used when selecting bread is its colour in terms of darkness (this usually
has a low L* value) or lightness (this usually has a high L* value). Breads
with xylanases from different sources were significantly lighter in colour
(as indicated by their higher L* values) than the control loaves bread
(p<0.05) (Fig. 3). The data reported in Fig.
4 indicate that the crumb were lighter than the control for all bread
loaves except the sample with M3 (xylanase from Trichoderma longibrachiatum,
64 U mg-1).
The positive b* values, which indicate yellow colour of crumb and crust
bread sample Fig. 5 and 6 demonstrate
that the crust bread samples with M3 and M1 were yellowier than the control
and other samples, for the crumb colour (in term of b* values) the data
did not show significantly effect by using xylanases.
There was a small difference of overall symmetry among the loaves (Table
1), Loaf with M3 had very smooth crust and loaf with M6 had many large holes,
which resulted in the bad uniformity. The stickiness of every loaf was not good,
as they were wet due to not enough resting time after baking. However, all of
them had good flavour and aroma of normal bread, M2 had the best performance
with good shape of loaf, smooth surface of crust, best uniformity of crumb cells.
|| The effect of addition xylanases on sensory analysis
of loaf bread
||The effect of addition xylanases on crumb b* value of
The results obtained show that the addition of xylanases could lead to
improved bread quality. In general, these enzymes significantly improved
loaf volume, loaf colour and crumb texture and firmness. Xylanases produced
from different types of microorganisms play various roles in baked product
quality. In the current study, xylanases from six different sources (M1
(from Trichoderma viride, 205 U mg-1); M2 and M3 (from
Trichoderma longibrachiatum, 64 and 132 U mg-1, respectively);
M4 (from Aspergillus niger, 79.3 U mg-1); M5 (from Humicola
insolens, 200 U mg-1); and M6 (from rumen microorganism,
405 U mg-1) were studied and they showed different positive
effects on bread characteristics, M6 have shown a great advantage particularly
in loaf volume of bread. It is believed that xylanase plays a major role
in converting the insoluble pentosan to soluble pentosan. The soluble
pentosans will bind with water about 10 times of their weight (Mannie,
2000). Water is released in the dough through the partial hydrolysis of
arabinoxylan by endoxylanase, as a consequence, the dough becomes softer
which leads to better ovenspring and larger volume of bread with a softer,
more delicate crumb (Poldermans and Schoppink, 1999). In relation to anti-staling
potential, all enzymes appeared to show good tolerance on bread firmness
compared with the controls. M3 could lower the firmness during 3 day storage.
In comparison, each type of enzymes had different effects on bread quality.
Furthermore, studies in the area of optimum levels of xylanases should
be done in greater depth.
The authors would like to thank the Applied Science University, Amman,
Jordan for their financial support, Appreciation is also due to Dr. Darryl
Small, RMIT University, Melbourne, Australia for his expert advice and
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