Baking and Confectionery Technology

Wheat Flour Milling

Wheat Flour? Wheat flour is a powder made from the grinding of wheat

used for human consumption.

Wheat flour is the most common flour used in baking. There are different types of wheat flour, and they're distinguished by the amount of gluten they contain.

Wheat is unique or its protein content (gluten).

What is Gluten?

Gluten is protein composite( gliadin and a glutelin) found

in foods processed from wheat and related grain species,

including barley and rye.

It gives elasticity to dough, helping it to rise  and to keep

its shape, and often gives the final product chewy texture.

It gives baked goods their structure. When dough is

kneaded, these glutens develop and become firm.

Where’s the Flour?

• Whole grain flour contains all grain parts

• Refined, enriched flours are made from the endosperm only

• Endosperm (83% of kernel)Energy for plant growthCarbohydrates; protein for people

• Bran layers (14.5% of kernel)

Protects seedFiber, B-vitamins; minerals

• Germ (2.5% of kernel)Nourishes seedAntioxidants, Vitamin E, B-vitamins

The basic aim of the milling process -to break the wheat grain, remove the outer bran layers and the germ .-to grind the pure endosperm into flour.

This is achieved by a gradual series of operations including -a breaking stage, -a reduction stage and -a series of separations of the ground material by means of both particle size and density.

THE MODERN FLOUR MILLING PROCESS

First wheat is cleaned and conditioned to a suitable moisture

level for milling before passing through the BREAK ROLLS.

The break rolls consist of pairs of fluted rolls running in

opposite directions at a differential speed so that both a shearing

and grinding action is produced.

The stock from the first roll is sieved in a plansifter and branny

material with endosperm adhering is separated and sent to the

next set of break rolls.

Wheat Flour Milling

Coarse endosperm chunks (SEMOLINA) and finer endosperm particles (MIDDLINGS) are separated in the purifier and sent to the reduction rolls.

Any remaining fine bran particles may be removed by the purifier using a combination or sieves and air currents.

Generally, four break stages are used with successively finer flutings and gap settings for each stage.

After the final break stage, bran is removed as commercial mill bran.The coarse endosperm particles are ground to flour using smooth

REDUCTION ROLLS. After each grinding, flour is removed by sieving in a plansifter and

overtailings of the sieves are sent to subsequent reduction rolls.

Wheat Flour Milling

The number of reduction stages depends on the flour yield required but in recent years, the number of stages has gradually been reduced by the use of impact equipment (flake disruptors, entoleters).

After the final reduction roll, any remaining fine bran, endosperm and germ is removed as POLLARD.

Germ is normally flattened on the reduction rolls and, in certain mills, separated by sieving.

The amount separated is generally less than 2%. Bran and pollard are sold as animal feeds, although bran and

germ are also packaged separately for human consumption.

Flour Milling

EXTRACTION RATE

The number of parts by weight of flour that is produced from one hundred

parts of wheat is termed the FLOUR YIELD or EXTRACTION RATE.

This figure is used as an index of the overall efficiency of a flour milling

system.

In practice, the limit of white flour extraction has been 75-79%;

Further they increases in the extraction rate lead to darker flour colour and

higher ash and fibre contents which adversely affect the breads baked from

them.

Milling to produce white flour results in the removal of varying amounts of

bran, pollard and germ which together constitute 12-15% of the grain by

weight.

The national average extraction rate has been reported as 75.8% with a range

of 69-80% depending on the efficiency of the mill.

DISTRIBUTION OF NUTRIENTS DURING MILLING

Wheat flour is an excellent source of complex carbohydrates.

Other than gluten flour, all types of wheat flour derive at least 80 percent of their calories from carbohydrates.

Depending on the flour type, the percent of calories from protein ranges from 9 to 15 percent, except from gluten, which has 45 percent protein content.

Flour, comprising about 75-78% of the total mill products, generally contains 90-95% of the grains protein, 50% of the thiamin (vitamin B1), and 30-60% of the minerals.

Bran and pollard contain most of the grains fiber and a variable amount of the vitamins and minerals.

Types of wheat Flour

1. Hard wheat flour: including hard white, hard red winter, and hard red spring wheat have a high protein content (ranging from 10 to 14 percent), which means the gluten forming capacity is also higher, suitable for baking yeast breads and similar products.

2. Soft wheat flour: include soft white and soft red winter, which are both used for products, such as cakes, cookies. The protein content of soft wheat varieties, such as cake and pastry flour, usually ranges from 6 to 10 percent.

3. Durum wheat flour : is the hardest wheat grown. It is used almost exclusively for making pasta and is most often ground into a granular flour with a light yellow color known as semolina,

Classifications of wheat flour based on gluten content and purposes of uses

1. All-Purpose Flour: All-purpose flour is formulated to have a medium gluten content of around 12 percent or so.

2. Bread flour is a strong flour, meaning that it has a relatively high gluten content — usually around 13 to 14 percent.

3. Cake flour is made from soft wheat and has a lower gluten content — around 7 to 9 percent. Its grains are visibly finer than bread flour, and it is much whiter in color. Its fine, soft texture makes it preferable for tender cakes and pastries

4. Pastry flour is slightly stronger than cake flour, at around 9 to 10 percent gluten. It can be used for biscuits, muffins, cookies, pie doughs and softer yeast doughs. It has a slightly more off-white color than cake flour.

NON-WHEAT FLOURS

Types of Flour Ground from CornSeveral varieties of corn are used to produce different types of corn flour. The degree in which the corn is milled and processed also determines the type of flour that is produced.

Corn Flour

A type of flour milled from dried kernels of yellow corn. Corn flour is very useful for gluten-free quick breads.

Because corn flour contains no gluten, it must be blended with wheat flour when preparing yeasted breads.

Types of Flour Ground from Rice Rice flour is produced from uncooked rice that has been

ground into a powder ranging from course to very fine. Rice ground to a course texture is often used in baked items such as cookies and cakes.

Standard rice flour is available in brown or white varieties.

Brown Rice Flour Brown rice flour is a type of flour made from rice kernels

that have been processed to remove the outer hulls, but not the nutritious bran layers covering the kernel.

When the kernels are ground into flour, the resulting color is only a shade darker than flour milled from polished rice and the texture is not quite as smooth.

White Rice Flour

White rice flour is a type of flour produced from grinding polished rice (the bran and germ have been removed) into a powder.

White rice flour can be used as a thickening agent for sauces and puddings.

It is also very popular for the preparation of a variety of Asian noodles.

It is used in some baked goods, such as cakes, cookies

Types of Flour Ground from Rye

Rye flour is produced from grinding the grains of rye into a powder.

Like most other types of flour produced from grains, rye flour may be ground into varying degrees of fineness ranging from course to very fine.

It also is available in light, medium, and dark varieties according to the quantity of bran included in the flour.

The type of protein necessary for gluten formation is lower in rye than wheat, but it is higher than in most other grains.

Rye flour is often combined with wheat flour when baking risen breads.

Light Rye Flour

During the milling process, the bran is removed from the rye to produce light rye flour, which is a lightly colored and very starchy version of rye flour. It is often used for making crusty black breads.

Medium Rye Flour

Medium rye flour contains some bran, but not as much as darker versions of rye flour. It is widely used in a variety of rye breads and other baked goods.

Dark Rye FlourDark rye flour is produced from the whole grain minus the husk. The bran and the germ are retained, which are full of nutrients.

Types of Non-Wheat Flour Ground from Other Grains

Barley Flour

Barley flour is usually produced from barley, which

refers to barley that has been scoured and polished to

remove the husk and the bran.

After the malting process has removed the sugar and

starch, the remaining barley (known as malted barley

flour), is steam dried, milled, and sifted to provide the

finished flour product.

Oat Flour

Oat flour is produced from hulled and cleaned oats. It is also ground from rolled oats or oatmeal. Oat flour adds texture and a rich nutlike flavor to breads and other baked goods

Seven-Grain Flour or composite flour:

Seven-grain flour is a commercially blended flour mixture of seven ground grains consisting of wheat, rye, corn, oats, barley, millet, and flax (or triticale). Usually used for the manufacturing of baked products.

Sorghum Flour

Sorghum, which has a sweet, nutty flavor, is often milled into flour, but it lacks gluten, so it isn't suitable for making yeast breads. 

Some other non wheat flours are:

buckwheat flour , casava flour, potato flour, chapati flour , chickpea flour