Question and Flour Problems : Storage (Wheat, Flour, Bread)

1.We noticed an increase in the temperature of the wheat to 45 ⁰C in parts of the silo during the winter. When we checked the wheat we couldn’t find any signs of infestation. What may the reason have been? Can we still use the wheat?

This phenomenon is probably due to self-heating caused by fermentation. This can occur if the wheat is not moved or sufficiently aerated during storage. If only a small amount is affected, the thoroughly mixed wheat can be used (unless the taste and smell are impaired), but the performance should checked. Unusually short dough properties indicate heat damage to a larger proportion of the wheat.

2. If the flour has been treated with enzymes/ ascorbic acid/ bleach, will its properties be maintained during storage? For how long?

Most enzymes except glucose oxidase and transglutaminase are very stable in the flour too. In most cases the shelf-life is restricted by the organoleptic properties of the flour rather than by its baking performance. Ascorbic acid slowly oxidizes to dehydro-ascorbic acid, which is the oxidizing agent to which ascorbic acid has to converted anyway before it has an oxidizing effect. A shelf-life of 6-9 months is no problem.

3. Why does flour milled from wheat of different ages behave differently when baked, although the age of the flour itself (i.e. number of days after milling) is identical?

Maturation does not only take place in flour; it also takes place in the intact grain, although the chemical and biochemical processes are probably different. Maturation can be observed every year with the new crop: The optimum dosage of oxidizing agents (maturing agents) is high when the new wheat is first milled and can be (or has to be) reduced after longer storage.

4. Is there any additive I can use to protect flour against insect infestation?

So far there seems to be no such additive. And there will probably always be an insect species that is not repelled by the treatment.

5. My flour forms lumps after a few weeks of storage, especially at the bottom of the bags. What can I do to prevent it?

This may be due to a slightly elevated moisture level in the flour. The granulation also plays a role in lump formation. Very fine particles tend to form lumps more readily (semolina is more free-flowing than wheat flour).

6. I am having problems with the microbiology of my wheat and fear they will impair the self life of my flour. What product might help?

If the flour has less than an even 15% moisture the microorganisms are unable to grow, so they cannot impair the shelf-life. On the other hand these microorganisms may just be a sign of inadequate cleaning of the wheat or failure to remove all the bran. If the lipid content of the flour is also high for this reason, the shelf-life will indeed be impaired. But we do not recommend treatment with chemical agents such as antioxidants.

The microorganisms may, however, play a role in the further processing of the flour. Especially if there is a large number of thermophilic spore formers (Bacillus subtilis, B. masentericus), some may survive baking and cause degradation of the crumb of the bread. Preservatives such as propionate, acetic acid and even vinegar may help.

7. Why does flour go rancid, and how can this be prevented?

At moisture levels above 15%, flours can go rancid because of the activity of fat-degrading enzymes. Storage at termperatures above 20 ⁰C also plays a role in the effectiveness of the enzymes. A moisture content below 14% reliably prevents hydrolysis of the fat in the flour because the aw value is then so low that the enzymes are only very slightly active.

8. How can we avoid rancidity?

The germ and the aleuron layer contain most of the flour lipids. If both are neatly removed while the germ is kept intact to avoid release of fat, rancidity will not occur during a reasonable period of storage. Furthermore, rancidity is triggered by exposure to light, moisture, heat and oxygen, so any condition reducing these factors also reduces rancidity.

9. The wheat has a strange, musty smell.  What is the reason? Can I use the wheat? How can I remove the smell?

The smell is probably caused by unsuitable transportation or storage conditions resulting in mould formation. If the damage is only superficial, thorough cleaning and milling with a low yield will remove most of the substance that smells. In the past, attempts have also be made to mix the grain with active charcoal in order to absorb the substance responsible for the smell. The charcoal was subsequently removed by sifting.

10. The flour has a strange smell. Where does it come from? Can I use the flour?

The off-smell may be a carry-over from the wheat (See question 9), or it may have been caused by unsuitable storage of the flour itself. There is no viable method for removing the smell from the flour. Adding it in small amounts to intact flour is probably the only way to use the flour.

11. The bread develops a strange smell during storage. What may the reason be?

This is probably due to the potato disease. Later on, the crumb will form slimy strands when broken open.