Question and Flour Problems : Colour

1.Although the ash content is only 0.5%, the flour has a dark colour. Why is that?

There are wheat varieties with a higher pigment content (compare, for instance, U.S. Hard Red Spring Wheat with U.S. Hard White).

2. How can I brighten the colour of the flour?

Chlorine, Chlorine dioxide (both are gaseous) or benzoyl peroxide (powder) can be used for bleaching. In contrast to chlorine and chlorine dioxide, benzoyl peroxide has almost no maturing effect on the flour. The treatment with benzoyl peroxide takes 24 – 72 h to become visible.

3. How can a brighter flour or bread crumb be obtained?

A brighter flour can be obtained with a lower extraction rate, because the outer layers of the wheat kernel contain more pigments. Once the flour has been produced, treatment with chlorine and chlorine derivatives achieves a brighter colour, but is not acceptable in many cases for various reasons.

The addition of benzoyl peroxide also results in a brighter colour, visible 24 -72 h after treatment of the flour.

The addition of enzyme-active soybean flour will make the bread crumb brighter due to oxidation of the pigments. Other additives such as ascorbic acid, oxidizing agents and hemicellulases create a finer crumb structure appears brighter because it reflects the light better.

4. How can I brighten the colour of the bread crumb?

Bleached flour will result in a brighter crumb colour. The same effect can be achieved with enzyme-active soybean or fava bean flour. In all cases the flour pigments are affected. Brightening with ascorbic acid, monoglycerides, hemicellulases and some other additives rests on a purely physical phenomenon: they reduce the pore size, i.e. they create a finer crumb structure. Smaller pores cast less shadow and therefore appear brighter.

5. My flour is white, the ash content is only 0.6%, but when a dough is prepared  a greyish darkening occurs. What is the reason?

In many cases this is due to metal residues in the flour, stemming from roller mills which are worn or badly adjusted.

6. The flour is bright, but there are dark specks. Where do they come from?

Check the sieves for holes.

7. Flours of the types 500 and 750 with relatively high Falling Numbers and a high gluten content without any additives sometimes produce strange results at bakeries. The rolls have a peculiar red colour, not slightly brown like the typical products (no Maillard reaction). Apart from that, all the parameters of the baked goods are ok. What could be the reason?

Possible reason are :

a.The wheat has been treated with a red dye. This was done in Germany to take the wheat out of the food market (market intervention). The dye was not poisonous.

b. Red Fusaria can also cause discoloration. This is a severe health risk and should be tested in microbial and toxin assays.

c. Strong peroxidase activity can also result in such discoloration. Some wheat and rye varieties are rich in peroxidase. This wheat cannot be used for fresh noodles because it leads to discoloration of the products. It is difficult to reduce peroxidase activity, but some effect can be achieved by modifying the pH, i.e. by adding alkaline or acidic buffering agents.

d. A high alkaline pH also results in a yellowish or even reddish discoloration. This effect is used to make yellow alkaline noodles in Asia. At a higher pH the Maillard reaction (non-enzymatic browning) also takes place faster and colour  formation (reddish or brownish) can therefore take place at lower temperatures, i.e. in the crumb.