What does plain flour contain?

November 15, 2025 •

4 min read

Did you know that plain flour, also known as all-purpose flour, consists solely of the wheat grain's starchy endosperm, with the bran and germ removed? This unique milling process is the key to understanding what plain flour contain and how it differs from other types.

Quick Summary

Plain flour is primarily composed of ground wheat endosperm, the starchy center of the grain. In many regions, it is enriched with vitamins and minerals to replace nutrients lost during milling.

Key Points

Milled Endosperm: Plain flour is made from the starchy endosperm of the wheat grain, with the bran and germ removed.
Medium Protein Content: It contains a moderate amount of protein (glutenin and gliadin), giving it balanced gluten potential for diverse baking applications.
Often Enriched: In many regions, the flour is fortified with nutrients like iron and B vitamins to replenish those lost during processing.
Bleached vs. Unbleached: The two types differ in their aging process; bleached flour uses chemicals for faster aging and a finer texture, while unbleached ages naturally.
Do Not Eat Raw: Raw plain flour can contain harmful bacteria and should always be cooked or baked before consumption.

The Core Ingredient: The Wheat Endosperm

Plain flour, or all-purpose flour, is a white, versatile powder made primarily from the grinding of wheat grains. The key to its composition lies in the milling process, where the wheat kernel is separated into its three main components: the bran, the germ, and the endosperm. Unlike whole wheat flour, which uses all three parts, plain flour is made exclusively from the endosperm. The endosperm is the starchy, interior part of the grain that contains the majority of the carbohydrates, a moderate amount of protein, and very little fiber. The removal of the nutrient-rich bran and germ gives plain flour its light color and fine texture, while also extending its shelf life.

The Role of Protein and Gluten

Within the endosperm are two specific proteins, glutenin and gliadin. A common misconception is that gluten is an ingredient in the flour. In reality, gluten is a substance that is formed when these proteins are hydrated and agitated through mixing or kneading. Plain flour is typically milled from a blend of hard and soft wheat, which gives it a moderate protein content, usually between 9-12%. This balanced protein level is what makes it so versatile, providing enough structure for some breads and pizza bases, while still being delicate enough for cakes and pastries.

How Gluten Affects Baking

The amount of gluten potential in flour directly impacts the texture of the final baked good. A higher protein content means more gluten can be developed, resulting in a chewy, elastic dough, ideal for bread. A lower protein content leads to less gluten formation, producing a tender, crumbly texture, perfect for cakes and biscuits. Plain flour's medium protein content places it perfectly in the middle, capable of a wide range of applications.

Fortification: Enriched Plain Flour

During the refining process, when the bran and germ are removed, many natural vitamins, minerals, and fibers are lost. To combat this, many governments mandate or encourage flour enrichment. This involves adding specific nutrients back into the flour. For example, in the UK, it is legally required for white and brown flours to be fortified with calcium, iron, niacin (vitamin B3), and thiamin (vitamin B1). These added nutrients help to restore some of the nutritional value lost during milling.

Typical Nutrients Added During Enrichment

Iron: Essential for red blood cell production.
Calcium: A mineral important for bone health.
Thiamin (Vitamin B1): A B vitamin crucial for cell function.
Niacin (Vitamin B3): A B vitamin that helps convert food into energy.
Riboflavin (Vitamin B2): Important for energy production and cellular function.
Folic Acid (a form of Folate): A B vitamin added to fortified flour to help reduce birth defects.

Bleached vs. Unbleached Plain Flour

When shopping for plain flour, you will often find two options: bleached and unbleached. Both start as the same milled wheat endosperm, but differ in their aging and treatment process.


Feature	Bleached Plain Flour	Unbleached Plain Flour
Aging Process	Artificially aged using chemical agents like chlorine or benzoyl peroxide to speed up the process.	Naturally aged by exposure to oxygen over a longer period.
Appearance	Whiter and brighter in color due to chemical treatment.	Off-white or pale yellow color that naturally fades over time.
Texture	Finer, softer, and more absorbent due to chemical modification.	Denser, more structured, and slightly coarser grain.
Ideal Uses	Works well for delicate, fluffy baked goods like white cakes, cookies, and pancakes.	Better for baked goods that require more structure, such as yeast breads, puff pastries, and eclairs.
Taste	Some very sensitive palates may detect a slight chemical aftertaste.	More neutral, natural flavor.
Cost	Generally less expensive due to the faster production process.	Often slightly more expensive due to the longer, natural aging process.

The Dangers of Raw Plain Flour

While plain flour is a staple ingredient, it is crucial to remember that it is a raw agricultural product and should not be consumed raw. Raw flour can carry bacteria, such as E. coli, which can cause food poisoning. Therefore, it is important to always cook or bake any dough or batter containing plain flour before eating. For those using raw flour for crafts or playdough, heat-treating the flour beforehand is a necessary safety precaution.

Conclusion: A Versatile Kitchen Staple

In summary, plain flour is a refined flour consisting of the wheat grain's endosperm. It is a versatile ingredient with a balanced protein content, allowing it to be used for a wide range of baked goods, from cakes to breads, as well as for thickening sauces and gravies. Depending on the region, it may be enriched with key nutrients lost during milling, and it can be purchased in either bleached or unbleached forms, each with slightly different properties suited for specific culinary tasks. The next time you grab a bag, you'll know precisely what plain flour contains and how its components contribute to your cooking. For more flour-related information, check out KitchenAid's guide to different flour types.

Frequently Asked Questions

The primary ingredient in plain flour is the wheat endosperm, which is the starchy, interior part of the wheat kernel.

Plain flour contains no added raising agents, whereas self-raising flour is plain flour with a chemical leavening agent, such as baking powder, already mixed in.

Bleached flour is chemically treated to speed up aging and whiten its color, giving it a finer texture. Unbleached flour is aged naturally, resulting in a denser grain and a slightly off-white color.

No, plain flour is not gluten-free. It contains the proteins glutenin and gliadin, which form gluten when mixed with water. For a gluten-free alternative, you would need to use flour made from other grains like rice or almonds.

Plain flour is labeled 'enriched' when nutrients like iron and B vitamins are added back to replace those lost during the milling process.

Yes, you can use plain flour for bread, but it has a moderate protein content and may not provide the same chewy, structured result as a higher-protein bread flour.

No, it is not safe to eat raw dough made with plain flour. Raw flour can contain harmful bacteria like E. coli and should always be cooked or baked before consumption.

Plain flour is extremely versatile and used for baking cakes, pastries, and biscuits, as well as for thickening gravies, sauces, and soups.