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(A.T. Hagan) wrote in message >...
> Can someone explain to me the mechanism by which using old flour in
> raised bread baking would lead to a lower volume, denser loaf?
Aging the flour will lead to maturation and later degradation of
If the flour is old that it smells musty the mechanism of its
degradation is contributed primarily by the fatty acids present in the
flour fat.These is done by the fat degrading enzymes as well as
oxidation- reduction enzymes such as the lipoxygenase , oxidases and
even protein degrading enyzmes;proteinases.
The flour aging starts the moment ( first stage)its stored and it
will achieve its peak when the reaction of the lipoxgenase with the
unsaturated fatty acids favors the strenghening of the wheat gluten
which is akin to oxidation improvement of the flour. That is the
point that is most beneficial to baking.
Later the second stage the amound of degraded fatty acids reach a
level that free radicals and other reactive decomposition components
will result that gluten strands become taut and less extensive and the
loss of elasticity results.
The gluten can still be formed during the hydration of flour protein
but its quality suffer due to combination of chemical and enzymatic
degradation which is a complex multistep reaction that originates from
the flour fat breakdown.
> I'm presuming it's because the gluten proteins have oxidized over
> time. Is this correct?
That is partly the reason as the tightening of the gluten is akin to
oxidation but has gone beyond the beneficial limit.
Another is at that state it is more sensitive to proteolytic
> If so, then I'm further presuming that removal of the oxygen would
> greatly retard any breakdown of the flour, at least so far using it to
> bake raised breads are concerned?
Removal of oxygen is not the solution, as the dough to be functional
need the sufficient oxygen and if you mixed the dough under high
vacuum the bread quality is inferior or similarly in pure nitrogen
atmosphere meaning that oxygen is required.
Some high speed machines mixes dough under partial vacuum but the
amount of oxidants needed is maximum. Which is the same reasoning that
there really is a need for oxygen in the dough development.
> This would be for refined white flour - all purpose or bread flour
It will be the same with all flours.But the defect is more obvious
with wholemeal and clear flours and less with the refined white flour
which can be classified in the patent category.Even with low ash
There comes the point that in overaged flour( regardless of the ash
level which )) the chemical reaction that ensues contributes to the
degradation of gluten quality.
The best solution for using overaged flour is to blend it with large
amounts normally aged flour or even freshly milled flour and you can
still obtain satisfactory baking peformance.
That can be confirmed by your baking tests.
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