Freshly milled flour has its limitations. Decades ago, millers and bakers would naturally age their flour, noting improved baking performance after several months of storage. For obvious reasons, this practice has been replaced by the addition of various additives to the flour by the flour miller.

The type and amount of additives used by the flour mill will vary with the type and grade of flour and its intended end use. Except for bleaching agents, many of these additives can and are added in various forms at the bakery to adjust for specific processing conditions or desired finished product characteristics. At the flour mill, these additives are incorporated directly into the flour stream by micro feeders and their presence is confirmed by the mill QA.

So why is flour treated? For three reasons: to add nutrients, to change its color, and/or to improve its baking performance. Flour additives can be grouped into four categories: enrichment, bleaching agents, maturing agents and enzymes.

Enrichment
During the milling process, some nutrients are removed when the bran and germ are separated from the wheat endosperm. Enrichment of flour adds back some of the vitamins and minerals lost during the refining process, and also provides folic acid fortification as mandated by the FDA in 1998.

If flour is to be enriched, the Code of Federal Regulations (CFR) for enriched wheat flour requires each pound of flour to contain 24 mg niacin, 20 mg iron, 2.9 mg thiamine, 1.8 mg riboflavin and 0.7 mg folic acid. Calcium enrichment is optional (960 mg per pound). Iron is added as either reduced iron (most common) or ferrous sulfate. At the mill, these vitamins and minerals are added as a dry pre-blend, allowing precise addition rates. The enriching of flour has no effect on the baking performance of the flour. It is for nutritional benefit only.

Bleaching Agents
Bleaching is a traditional milling and baking term used to refer to both the whitening of flour and the aging or maturing of flour. For this discussion, the term bleaching will be used to describe only the whitening of flour. Freshly milled unbleached wheat flour is creamy in color. This color is thought to be undesirable in some applications. Bleaching agents oxidize the pigments naturally found in flour producing a whiter color. The two most common bleaching agents used are benzoyl peroxide and chlorine gas. Benzoyl peroxide can be applied to both hard wheat and soft wheat flours in powder form. It is a very effective bleaching agent, but its reaction is relatively slow, requiring 24 hours to 48 hours to completely react with the flour pigments. It has no appreciable effect on the baking performance of the flour. Flours treated with benzoyl peroxide are labeled as "bleached."

Chlorine gas is unique in that it acts as both a bleaching agent and a maturing agent. It is typically applied only to soft wheat flours, but does have some application with low protein hard wheat flours. The chlorine is applied to the flour at the mill as a gas. In addition to its whitening effect, chlorine also modifies the protein and starch, improving the baking performance of the flour, particularly in cake and cookie type products. Flours treated with chlorine are often also treated with benzoyl peroxide to further whiten the flour. Flours treated with chlorine are labeled as "bleached."

Maturing Agents
The term maturing implies aging. Aging of hard wheat flour improves its dough forming and gas retention properties. To facilitate this aging effect, wheat flours often contain various maturing agents. The three most commonly used at the mill level are azodicarbonamide (ADA), ascorbic acid and potassium bromate. These oxidizing agents are inactive in the flour but react in the dough. Bread and roll products made with these maturing agents will typically exhibit increased dough strength, better processing tolerance, increased loaf volume, and improved cell structure and symmetry. Although each of these additives contributes to these stated improvements, they react at different times within the bread-making process.

The reaction rate of ADA is relatively rapid, improving dough strength predominantly in the mixer. ADA may be added to the flour at levels up to 45 ppm. Ascorbic acid is intermediate in its rate of activity, starting in the mixing bowl and continuing its dough strengthening effect throughout most of the dough phase. Ascorbic acid is permissible in flour up to 200 ppm. Because it is destroyed in the oven, ascorbic acid (Vitamin C) cannot be declared on the nutritional panel. Potassium bromate reacts late in the bread making process (proofing and baking), providing strength when it is most needed. It may be added to a maximum of 50 ppm to flour. he use of potassium bromate has diminished over the years and is being replaced with ascorbic acid, other oxidizing and dough strengthening ingredients and specific enzyme technologies.

Ascorbic acid and potassium bromate must be declared on the ingredient declaration when added to the flour. However, azodicarbonamide is declared as a bleaching agent, although its function is one of maturing and not whitening.

Enzymes
Enzymes are keys to fermentation. Amylase enzymes help convert damaged starch (created during the milling process) into simple, fermentable sugars (sugars capable of being metabolized by yeast). These sugars are necessary for yeast fermentation, resulting in the production of carbon dioxide gas, ethanol, acids and many flavor compounds unique to yeast leavened baked goods.

Amylase enzymes are naturally present in wheat flour. However, they are not present in sufficient quantity to effectively carry out the fermentation process. Millers (and bakers) will supplement the low level of amylase enzymes with the addition of malted barley flour, malted wheat flour or fungal amylase enzymes. These additions will be declared on the ingredient legend of the flour. By standardizing the flour’s amylase activity, millers ensure consistent baking quality of the flour.

Some millers and bakers prefer the use of fungal amylase enzymes over malted barley flour. Benefits of treating with fungal enzymes include more uniform activity and thus improved mixing and fermentation control. The temperatures at which the fungal amylase enzymes are deactivated are lower than cereal (malt) enzymes. For this reason, modified methods are used to measure the enzyme activity and care must be taken when comparing values for flour treated with malted barley.

It is common industry practice to treat flour at the mill. Depending on the type and grade of flour, and the customer’s specifications, enrichment, bleaching agents, maturing agents and enzymes can be added to the flour. These additives function to enrich the flour, whiten the flour or improve the flours baking performance. For additional assistance or questions, contact your local flour sales or technical service representative.