29.2 Wheat, milling and the kinds of flour

Wheat through history

Grains of wheat, millet and rye about 10,000 years old have been dug up where lake dwellers once lived in Switzerland. The Romans perfected the rotary mill for grinding wheat. By the time of Christ the city of Rome had over 300 bakeries, and Roman soldiers carried wheat across the empire. Milling stayed rough for a long time: even flour milled twice and bolted, meaning sifted through silk gauze, came out yellowish, uneven and spotted with bran and germ.

The big change came in the second half of the 1800s. Edmund LaCroix, an American inventor, added a purifier that took the middlings (bran, germ and other coarse bits) away from the fine particles that make smooth white flour. More recently, whole grain flour has come back into demand because whole grain foods have proved more nutritious than white-flour ones.

Large-scale wheat farming in Canada began only after settlers moved onto the Prairies in the 1800s. Hard wheats such as Red Fife, Marquis and Selkirk made Canada a granary for Britain and much of Europe. Most wheat in Western Canada today is hard red spring; soft red and soft white wheats grow mainly in Quebec and Ontario.

Across North America, wheat grows mostly on the Canadian Prairies and on the Great Plains of the United States. Winter wheat grows from Nebraska southward; northward through Saskatchewan, spring wheat takes over. Kansas, home of the American Institute of Baking, sits at the heart of American wheat country, and Saskatchewan is its Canadian match.

What the miller is after

Milling turns whole grain into flour. A miller wants three things: flour that is the same every time, a range of flours for different jobs, and flours that behave predictably in the bakery.

The first step is to analyze the incoming grain, for example its gluten content and its amylase (a starch-digesting enzyme) activity. That analysis decides how grains will be blended. Milling then runs in three stages: cleaning and conditioning, breaking, and reduction.

Stage 1: cleaning and conditioning

Wheat arrives carrying weeds, seeds, chaff and other matter.

• An aspirator blows strong air through the grain to lift out light rubbish.
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• A disc separator removes barley, oats and other unwanted grains.
• Scourers use metal beaters to throw the wheat hard against perforated steel. This knocks loose the dirt packed in the crease of each kernel, and a blast of air carries it off.
• A magnetic separator pulls out any iron or steel.
• The wheat is dampened, and machines called whizzers spin off the wet on the surface.
• The grain is tempered: left damp in bins for a short while so the bran toughens and can be peeled away cleanly from the part that makes flour.
• Last, the wheat is warmed to an even temperature, ready for breaking.

Stage 2: breaking

Breaking has two aims: get as much bran and germ as possible away from the endosperm, and get as much flour as possible from that endosperm. A home grain mill does the job in one pass. A commercial mill works in many small steps, so very little bran or germ ends up mixed into the endosperm.

The stage is called crushing, but large steel rollers actually crack the wheat. The first rollers are ridged, or corrugated, and split the grain into coarse pieces. These pass through screens that get finer and finer, while moving air draws off impurities. The coarse pieces of endosperm, between semolina and flour in size, are the middlings. The bran and germ are sifted off, and the coarse stock goes round again: more rolling, sifting and purifying.

Taking out the bran and germ gives a flour that makes better dough and has a better color. It also helps the flour keep, since the oil in the germ can spoil it.

Stage 3: reduction

Now the coarse particles pass through finer sieves and rollers. Once the first crushing is done, the stock is split into five or six streams. The machines that do this are plansifters: stacks of sieves, each with a different mesh, the finest as fine as finished flour. Some flour is already made at this early point.

Each stream then goes through purifiers, rows of flat sieves set at a slight slope with air blowing upward to clear the dust. The stock is crushed a little more and sifted into many more parts. Perfectly smooth steel rollers make the last crushings, turning middlings into flour.

The new flour is bleached and held in bulk storage. It is then enriched with thiamine, niacin, riboflavin and iron, and either bagged for homes and bakeries or loaded for bulk delivery.

Extraction rate

Flour streams

A modern mill makes about 25 separate streams of flour, each a little different in quality and make-up. These are combined into four kinds of flour people eat, plus streams sold as animal feed.

One measure used to grade them is ash: the minerals, such as phosphorus, left behind when flour is burned. The more refined the flour, the lower its ash.

Kinds of wheat flour

Each edible stream yields several flours, each with its own character and uses.

A miller's specification sheet tells a baker what is in a flour. One Canadian bread flour, for example, lists these ingredients:

• wheat flour
• amylase
• ascorbic acid
• the vitamins niacin, thiamine mononitrate, riboflavin and folic acid
• iron
• azodicarbonamide

That flour has 14.2% moisture, 0.54% ash and 13.00% protein. The sheet also carries microbe test results and an allergen statement. The protein figure is worked out in the laboratory from the flour's nitrogen.

Semolina, triticale and no-time flour

Semolina is the gritty product made of small bits of endosperm from durum wheat. The same bits from other hard wheats are called farina. The best-known semolina on store shelves is a hot wheat breakfast cereal. Semolina as the flour for dried pasta is covered with pasta. see chapter 16: Italian-style pasta

Triticale is a cross between wheat and rye that brings together the best of both. It was the world's first new grain and is now a commercial crop in Manitoba.

Bakers have always wanted to save time and money without losing quality, flavor or structure. No-time flour is the millers' answer: flour treated with additives (ascorbic acid, bromate and cysteine, for example) that does away with bulk fermentation, for both the sponge method and the straight dough method. It saves time, labor and floor space, and a baker can keep their own formulas with small changes.

Blending flours

Weather changes the grain from year to year. If harvest time is damp, for instance, grain can start to sprout, which leads to damaged starch. Mills test and test-bake their flours and blend them to make up for this, so the flour a baker receives stays fairly constant. When something goes wrong with a bake, the flour is seldom to blame; the baker usually is.

Bakers blend too. Some soft flour mixed into bread flour makes a Danish pastry or a sweet dough less tough. Gluten flour is added to multigrain bread to help it rise.

Bleached, enriched and pre-sifted

Freshly milled flour, even fine flour, runs from yellow to cream in color, and its doughs tend to be sticky and hard to handle. Kept well, flour gets better in color and quality as it ages, for up to a year.

Storing flour that long costs money. So, near the end of the 1800s, millers began treating fresh flour with oxidizing agents to whiten it and make it handle like aged flour. These bleaching and maturing agents leave the flour's food value unchanged. They include:

• chlorine dioxide
• chlorine gas with a little nitrosyl chloride
• ammonium persulfate
• ascorbic acid

Two kinds of bleach are used. An organic peroxide whitens only the yellow pigment and leaves the gluten alone. Chlorine dioxide, used more than any other in North America, whitens the pigment and also improves the gluten, but it destroys the tocopherols (the vitamin E group).

Enriched flour has had iron and three key B vitamins (thiamin, riboflavin and niacin) put back after milling removed part of them. Enrichment does not change the taste, color, texture, baking quality or calories of the flour.

Pre-sifted flour has been sifted many times at the mill through extremely fine silk. The mesh differs by flour. Cake flour goes through a finer mesh than bread flour, so a cup of cake flour holds more tiny particles, packs denser and weighs a little more than a cup of bread flour. Sifting also matters in the bakeshop: bread made with sifted flour rises to a bigger volume, because of the extra air.

Flour additives

Many additives work better in combination, which is why commercial flour may carry several. Some act as dough conditioners and some help fermentation. Countries differ in what they allow: in Germany, ascorbic acid is the only additive permitted.

• Bromate made flour age, or oxidize, much faster. It was used until the early 1990s; Canadian millers stopped after the U.S. Food and Drug Administration raised health concerns. In the United States some states allow it and others, such as California, ban it.
• Azodicarbonamide (ADA) has been approved in the United States since 1962 and is permitted as a food additive elsewhere too, but is banned in Europe. It works fast and gives a dry, cohesive dough that can take up a lot of water. It is not a bleach, but the finer texture it gives makes the crumb look whiter. It destroys no vitamins. A baker can ask the flour supplier whether a flour contains ADA or other chemical additives.
• L-cysteine is an amino acid that speeds up reactions in the dough, cutting bulk fermentation nearly to nothing and giving a "no-time" dough. It makes dough more elastic and better at holding gas.
• Ascorbic acid is vitamin C. It was first used to improve bread in 1932, after bakers noticed that old lemon juice in a dough helped it hold gas and rise higher. Too much does no harm, because the heat of baking destroys the vitamin. It is now added as a matter of course to some North American flours meant for artisan bread.
• Calcium peroxide is another agent that matures dough. It is a different thing from the peroxide used to bleach flour.
• Glycerides go into cake mixes and yeast doughs. They are surfactants, short for "surface-acting agents". In bread they mainly keep the crumb soft, which slows staling, and they strengthen the dough a little.
• Sodium stearoyl lactylate, approved in the United States since 1961, helps dough hold gas, shortens proofing, gives a bigger loaf and slows staling.

Whole grain and artisan milling

Before shoppers came to want smooth white flour with additives to age it fast, flour was milled the whole grain, artisan way. Artisan flour differs from the white kind.

• It is less refined.
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• It has few or no additives.
• It keeps more nutrition.
• It suits traditional breads.

Demand for it, and for whole grain flour made from the entire grain, is growing.

Artisan millers, also called micro millers, grind many grains the big mills do not, such as spelt, kamut and buckwheat, along with other grains and pulses that have no gluten. Bakers can buy from them directly or through a distributor, and knowing where a grain came from matters to an artisan baker. Many of these millers buy straight from farmers, which builds trust and makes growing and food safety practices easier to see.

Their grain may be grown conventionally or organically. Certified organic grain has passed a demanding process that guarantees no chemical additives. When a whole grain flour with little refining is wanted, stone mills and impact hammer mills are the usual methods.