Chemistry Reference
In-Depth Information
HO
HO
O
O
OH
HO
O
O
O
HO
HO
OH
OH
O
HO
HO
HO
HO
O
O
O
n
OH
OH
OH
O
O
O
HO
HO
Endocellulase
OH
OH
OH
O
O
OH
n
HO
Cellulose
O
O
O
HO
HO
OH
OH
O
Exocellulase
HO
n
Cellulose (crystal)
HO
HO
HO
Cellobiase
(
β
-glucosidase)
O
O
O
OH
OH
OH
HO
OH
HO
O
OH
OH
OH
OH
Glucose
Cellobiose or cellotetrose
Fig. 6.13
Cellulose breakdown by endo- and exo-cellulases and cellobiase.
made up of lignin, cellulose and hemicellulose or water unextractable (WU) arabinoxylans.
Wholemeal flour contains the entire seed of a plant and thus antioxidants, vitamins and
fibres, which are beneficial to human health. Refined flour, used for standard white bread,
has normally had the bran and the germ removed leaving only the endosperm.
The high fibre content of wholemeal bread may influence the dough consistency and
weaken the gluten structure. This will ultimately lead to high water absorption, loss of
extensibility and reduced fermentation tolerance. The final bread may show a reduced loaf
volume, increased crumb firmness and a less pleasant taste and flavour. In addition, the crumb
will be less white compared to normal bread.
Baking enzymes are therefore added to wholemeal formulations to improve dough and
bread characteristics. In addition to the above-mentioned enzymes, cellulases are slowly find-
ing their way into some bakery applications. The addition of cellulase enhances crumb struc-
ture, resulting in a more regular and fine crumb and, consequently, improved whiteness.
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The positive effect is due to break down of cellulose fibrils enabling better gluten devel-
opment and improved proofing stability, increased dough tolerance and enhanced volume,
texture and appeal in wholegrain bread types.
One of the relevant enzyme activities present in normal cellulase preparations is a CBH
with bread improving activity.
205
The most important effects are an improved bread vol-
ume and an improved crumb structure, which are not accompanied by bad dough-handling
properties due to stickiness of the dough (Table 6.7).
Like most sectors of the food industry, the bakery market has been presented with the
opportunity of rising demand for healthy 'wellness' products promising nutritional benefits.
Since consumption of whole grains has been linked to improvements in cardiovascular health
as well as reducing the risk of certain cancers and lowering blood pressure, this move towards
