Chemistry Reference
In-Depth Information
It is well known that bread volume has a clear relationship with crumb softness. Higher
specific volume leads to a softer bread crumb. Fine crumb structure with thin cell walls
gives a softer crumb than a coarse structure with thick cell walls.
Formulation also has a clear influence on staling since any ingredient, like shortening,
having an effect on volume will also have an effect on softness.
Processing has a certain influence on staling as well. Sponge and dough processing gives
a different structure and softness compared with straight dough processing. In the same
way a twisting step, resulting in a finer and more uniform crumb, will also positively
affect softness.
Finally, storage conditions play a role in staling since storage at lower temperature en-
hances starch retrogradation and thus will have a clear influence on crumb softness.
In the beginning of this century, the extended shelf life (ESL) concept was introduced in
the US. This concept used already existing enzyme technology in order to achieve dramatic
improvements in industrial bread making. These improvements were significantly ESLs for
industrial bread up till 11 days, strongly reduced stale bread returns and also strongly reduced
logistic complexity and costs due to a reduced number of transport routes.
68
The most visible applications of ESL have been in bread and, to a lesser extent, in snack
cakes. However, important improvements are also feasible in other grain-based food products,
ranging from cookies via cakes to frozen dough products.
Following these improvements, the demand for even longer shelf lives became obvious.
The objectives for further ESL developments can be found within four major areas
69
:texture,
flavour, microbial stability and crumb moistness.
With regards to texture, with the use of specific enzymes, like bacterial amylases or
intermediate stable maltogenic amylases (see section on amylases) sufficient softness can
be obtained. However, sufficient crumb elasticity (or crumb resilience or crumb springiness)
is more difficult to achieve. Since it is not fully understood which structures determine
resilience, that is gluten, starch, amylopectin, modified amylopectin, etc., it is extremely
difficult to find enzymes and/or ingredients which positively influence resilience.
When bread is kept for a longer time, a stale bread flavour develops and the well-known
fresh bread flavour and aroma disappear.
70
Removal or masking of this stale flavour is
a prerequisite for ESL. Keeping bread soft for a longer period may be feasible by using
proper enzymes, but the microbial deterioration has to be suppressed. Increasing the level
of propionate in the dough is not an option, due to problems with taste and yeast growth.
Longer storage times will result in enhanced evaporation of water from the crumb, via the
crust to the outside, thus leaving an unacceptable dry crumb. Specific precautions are needed
in order to prevent this.
Further, ESL developments will lead to highly interesting opportunities for industrial bak-
ing. Merchandizing, for example showing bread on displays in groceries and supermarkets,
baking to inventory - just as is done for cookies and biscuits - and further optimization of
distribution and transportation are currently being discussed.
Fungal amylases have limited effect on staling. These enzymes act predominantly on
damaged starch, but at the temperature at which starch starts to gelatinize, fungal amylases
are already inactivated and thus cannot act on starch when it has become accessible.
Bacterial amylases are much more heat stable and these enzymes have a significant ac-
tion on gelatinized amorphous starch. Modification of gelatinized starch results in a clear
anti-staling effect. However, since bacterial enzymes are extremely heat stable, these
