Wheat flour in baking explained

Introduction

What we call flour in baking often refers to different blends of wheat flour. Wheat flour is produced as a powder by grinding cereal grains and is by far the most commonly and vastly produced flour for human consumption and this particular flour is the topic of this blog post. However, there will be future posts discussing the properties of other types of flours, including rye, corn, rice, potato, almond etc. But for now, let’s focus on wheat flour properties and its role in baking! The type or types of flour used in baking are mostly determined by 1: the quantity and quality of gluten content, 2: other ingredients that have been incorporated and 3: the fineness of the flour. So to understand flour, we need to understand gluten, what it is and what it does.

Gluten

Flours contain two main components, starch and protein. One protein in particular is highly abundant; this is gluten, which can form 7-14% of total protein content in wheat flour. Gluten is a viscoeleastic protein, and it literally means it has both elastic and viscosity properties. These properties are results of its composition from two different polypeptides or proteins, gliadin and glutenin. In broad terms, gliadin contributes towards the viscosity whilst glutenin provides elasticity. The physical properties of dough are partially dependent on the ratio between gliadin and glutenin level. However, it has been observed by others that the rheological properties (liquid, solid state) of dough are also dependent on the amount of water used, methods of mixing, mixing time and resting time, suggesting a set of highly complex chemical reactions in dough. It is speculated before the addition of water to the flour, gliadin and glutenin exist as separate proteins and in the presence of water they combine to form gluten. The general rule is, the higher the gluten content, the more strength it will provide to dough. How gliadin contributes to coeliac disease is also a heavily researched area, but we will not discuss this in this post.

What we have no control over

There are things we have absolutely no control over and this is the quality of wheat and the milling process. The conditions in which the wheat was grown in such as soil, light availability and nutrients all play a role in the growth of wheat and subsequently affect the quantity and quality of gluten present. The milling process, i.e. how the wheat was ground, can affect the degree of bran and endosperm (Fig 1) separation and the properties of the final product. However, these are all things we, as consumers have no control over and have to rely the manufacturers to do their job properly, but it is worth bearing these in mind when a new batch of flour you got does not perform as well as your previous one.

Common types of wheat flour

Strong (bread) flour

This is probably the flour that you can purchase that contains the highest percentage of gluten, at around 13% or even slightly higher in some cases. These are almost always made from hard wheat, i.e. wheat with a hard kernel or seed of the plant. The higher level of protein present also allows the protein strands to entrap more CO₂ produced during the proofing

process by yeast.

Plain (all purpose) flour

This type of flour contains about 10-12% gluten and it’s the most versatile flour you will encounter (hence the name). It can be used for cakes, pastry and bread.

Self-raising flour

This flour is odd, it’s actually the same as plain flour but with about 2-2.5% (w/w) raising agents added to it to help with the rise of the batter.

Cake flour

This flour very often confuses people, many people believe it is the same as self-raising flour, but it’s not. It contains an even less gluten content compared to self-raising flour, which contains the same level of gluten as plain flour. Cake flour contains 7-9% gluten and in theory, should be finer than plain flour and the bran should be completely separated from the endosperm. Cake flours are normally bleached, which allows the cake to be lighter and a higher amount of sugar to be used. However, the use of many bleaching chemicals on flour is prohibited by the European Union.

That’s it for now, next time, I will be going through the raising agents in cakes, chemical structures and reactions, general proper science!