A Closer Look at Flour: From Ingredient to Meal

This longer reference provides the background behind the topic. Read it alongside the recipe collection when you want to connect an ingredient or food idea with a dish to prepare.

In this story

Overview Degermed and heat-processed flour Production Composition of cereal flour Bleached flour Bread flour More types

Overview

Flour is a powder used to make many different foods, including baked goods, as well as thickening dishes. It is made by grinding grains, beans, nuts, seeds, roots, or vegetables using a mill.

Cereal flour, particularly wheat flour, is the main ingredient of bread, which is a staple food for many cultures. Archaeologists have found evidence of humans making cereal flour over 32,000 years ago. Other cereal flours include corn flour, which has been important in Mesoamerican cuisine since ancient times and remains a staple in the Americas, while rye flour is a constituent of bread in both Central Europe and Northern Europe. Cereal flour consists either of the endosperm, germ, and bran together, known as whole-grain flour, or of the endosperm alone, which is known as refined flour. 'Meal' is technically differentiable from flour as having slightly coarser particle size, known as degree of comminution. However, the word 'meal' is synonymous with 'flour' in some parts of the world.

The processing of cereal flour to produce white flour, where the outer layers are removed, means nutrients are lost. Such flour, and the breads made from them, may be fortified by adding nutrients. As of 2016, it is a legal requirement in 86 countries to fortify wheat flour.

Nut flour is made by grinding blanched nuts, except for walnut flour, for which the oil is extracted first. Nut flour is a popular gluten-free alternative, being used within the "keto" and "paleo" diets. None of the nuts' nutritional benefits are lost during the grinding process. Nut flour has traditionally been used in Mediterranean and Persian cuisine.

Bean flours are made by grinding beans that have been either dried or roasted. Commonly used bean flours include chickpea, also known as gram flour or besan, made from dried chickpeas and traditionally used in Mediterranean, Middle Eastern and Indian cuisine. Soybean flour is made by soaking the beans to dehull them, before they are dried (or roasted to make kinako) and ground down; at least 97% of the product must pass through a 100-mesh standard screen to be called soya flour, which is used in many Asian cuisines.

Seed flours like teff are traditional to Ethiopia and Eritrea, where they are used to make flatbread and sourdough, while buckwheat has been traditionally used in Russia, Japan and Italy. In Australia, millstones to grind seed have been found that date from the Pleistocene period.

Root flours include arrowroot and cassava. Arrowroot flour (also known as arrowroot powder) is used as a thickener in sauces, soups and pies, and has twice the thickening power of wheat flour. Cassava flour is gluten-free and used as an alternative to wheat flour. Cassava flour is traditionally used in African, South and Central American and Caribbean food.

Degermed and heat-processed flour

An important problem of the Industrial Revolution was the preservation of flour. Transportation distances and a relatively slow distribution system collided with natural shelf life. The reason for the limited shelf life is the fatty acids of the germ, which react from the moment they are exposed to oxygen. This occurs when grain is milled; the fatty acids oxidize and flour starts to become rancid. Depending on climate and grain quality, this process takes six to nine months. In the late 19th century, this process was too short for an industrial production and distribution cycle. As vitamins, micronutrients and amino acids were completely or relatively unknown in the late 19th century, removing the germ was an effective solution. Without the germ, flour cannot become rancid. Degermed flour became standard.

Degermation started in densely populated areas and took approximately one generation to reach the countryside.

Heat-processed flour is flour where the germ is first separated from the endosperm and bran, then processed with steam, dry heat or microwave and blended into flour again.

Production

Milling of flour is accomplished by grinding grain between stones or steel wheels. Today, "stone-ground" usually means that the grain has been ground in a mill in which a revolving stone wheel turns over a stationary stone wheel, vertically or horizontally with the grain in between.

Roller mills replaced stone grist mills in the 19th century. The production of flour has historically driven technological development, as attempts to make gristmills and flour mills more productive and less labor-intensive led to the watermill and windmill. These terms are now applied more broadly to uses of water and wind power for purposes other than milling. More recently, the Unifine mill, an impact-type mill, was developed in the mid-20th century.

Composition of cereal flour

Flour contains a high proportion of starches, which are a subset of complex carbohydrates also known as polysaccharides. The kinds of flour used in cooking include all-purpose (North America) or plain flour, self-rising (North America) or self-raising flour, and, in North America, cake flour. The higher the protein content, the harder and stronger the flour, and the more it will produce crispy or chewy breads. The lower the protein, the softer the flour, which is better for cakes, cookies, and pie crusts. Cereal flour consists either of the endosperm, germ, and bran together (whole-grain flour) or of the endosperm alone (refined flour).

Bleached flour

"Bleached flour" is "refined" flour with a chemical whitening (bleaching) agent added. "Refined" flour has had the germ and bran, containing much of the nutritional fibre and vitamins, removed and is often referred to as "white flour".

Bleached flour is artificially aged using a "bleaching" agent, a "maturing" agent, or both. A bleaching agent affects the carotenoids responsible for the natural colour of the flour; a "maturing" agent also affects gluten development. A maturing agent may either strengthen or weaken gluten development.

This is still available in North America, but has been banned in Europe, Australia and New Zealand.

Bread flour

Bread flour is typically made from hard red winter wheat planted in the fall and harvested in the spring. Hard wheat is high in gluten, a protein that makes dough stretchy. Hard wheat is 11.5–13.5% (12–14% from second source) protein. The increased protein binds to the flour to entrap carbon dioxide released by the yeast fermentation process, resulting in a better rise and chewier texture.