Old flour

Aging the flour will lead to maturation and later degradation of flour.

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.

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 enzymes .

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.

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 flours. 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. Roy

OK, so if I'm understanding this correctly it's not simply a matter of oxidation breakdown but also a matter of other enzymes that do not need the presence of free oxygen in order to function? This seems in keeping with other aspects of food storage. Oxidative rancidity is the primary cause affective shelf-life but once that is addressed there are still other causes that eventually will do the same damage, just in a larger time frame.

Further, refined white flour suffers the same problems as whole-wheat flour but at a slower pace because it's fat content is much reduced, but not completely eliminated.

I'm looking at this as two seperate problems.

The first is how to keep flour in good condition while in storage, or at least getting a feel for how long it can be stored before it really begins to go off. White flour specifically - we'd just mill whole-wheat flour on the spot. This particular flour that I'm dealing with wasn't supposed to be kept so long but between the time I purchased and repackaged it and now circumstances changed and we ended up keeping it a lot longer than originally anticipated. If I had planned on keeping it this long at the time of purchase I'd have packed it with some oxygen absorbers which would have given me a longer shelf-life, but as you seem to be pointing out even in a no-free-oxygen enviroment other processes will still be ongoing that puts a definite limit on shelf-life. I am presuming the only thing that would affect that would be to lower the temperature of the storage area. Not really an option for me, but others might be able to do so.

The second would be in the dough itself. I'm thinking that the act of measuring and mixing the dry ingredients before incorporating the liquid ingredients would reoxygenate the flour. Is this correct?

This is what we're doing with the old white bread flour. Mixing in small quantities into the whole wheat flour we're making bread with. We seem to be getting good rises this way and the bread is pretty good.

Do you know of any place on the Internet that I could go and read up on this that doesn't require a cereal chemist's knowledge depth to understand?

.....Alan.

-- Curiosity killed the cat - lack of it is killing mankind.

i am not aware if there is an internet link that could provide you more information related to your questions. It is certain that.... You can only get more information from the food science related library. Roy