When you say the word protein, many people think instantly of the obvious proteins – meat, dairy, or those shakes that body builders drink. But wheat contains protein too. In fact, there are lots of different kinds of protein in wheat. We all know about gluten, but this is just one of them.
What are proteins?
Proteins are large molecules, formed from chains of amino acids – often called the building blocks of protein. The structure and function of a protein is determined by the types of amino acids it contains and their sequence in the chain. In the body, proteins are used for growth and tissue maintenance, they are key in promoting biochemical reactions and breaking down larger molecules, some provide structure to cell walls, help maintain pH and fluid balance and act as a source of energy.
Nutritionally, there are 20 amino acids. Of these, eight are essential amino acids, meaning that our bodies can’t synthesise them and we have to get them from our food. Most flours, apart from quinoa, don’t contain a full complement of these essential amino acids. This is one of the reasons I use quinoa in my main porridge recipe. Having the complete set of essential amino acids makes quinoa nutritionally very valuable. By including this porridge in my diversity and porridge breads, I’m ensuring high levels of nutrition, as well as great flavour. Because there is such a wide range of proteins, a number of classification systems have been developed to help simplify things. Using one of these methods, we can think of proteins in wheat as storage proteins (gluten) or structural proteins (non-gluten).
Gluten is the main storage protein in wheat. Storage proteins are important both for the plant and for us as bakers. To understand why, you have to remember that flour is made from ground up seeds. The storage proteins found in the seed are there to provide the energy it needs to germinate and grow. These proteins are structured to make them hard to break down, keeping the seed’s food reserve safe until it is needed. But each seed contains all enzymes required to break down the protein and release energy to the growing seedling.
As bakers, we are interested in the effects of the storage proteins on our baking. This group of proteins determines both the overall protein content of a flour and its baking qualities. It is gluten that gives dough that amazing, stretchy, elastic property, allowing your dough to capture the air produced by yeasts and expand as it proves and bakes. Gluten is formed from two parts – glutenins and gliadins. It’s when you add water to the flour that the magic happens. The glutenins and gliadins form bonds through a series of chemical reactions and the strength of those bonds is essential for a baker because they help capture the air in pockets within the dough, making the bread bouncy, light and structured.
Glutenins and gliadins are found in the starchy endosperm (the seed’s food reserve) of wheat, rye, barley and oats. They form strong and elastic bonds, and that strength is essential to the structure of a dough. I like to think of the glutenin as a modern-day rugby player – they have to run, as well as be flexible and strong. Whereas the gliadin is soft and flexible, more like a ballerina. The gliadin is one of the main reasons you can make these incredible stretchy breads that have that lovely open structure. Once you add water to make a dough, the glutenins and gliadins start forming that network of bonds essential for dough development.
Structural proteins act more like a scaffolding. They include albumins, globulins, and enzymes. Albumins make up between 5–13% of the total protein content in wheat flour, and globulins 5–11%. These proteins have two main functions in the seed – providing nutrients for the embryo as it germinates and acting as an in-built system to protect the seed from insects and pathogens. Enzymes have the important role of breaking down the food reserves into simpler molecules. I often describe enzymes as being like a biological Edward Scissorhands – they chop up complex molecules. The enzymes in wheat are amylases, lipases, proteases and oxidases. They only make up a tiny percentage of the total protein content of flour, but they are a major factor in determining the rate of fermentation in sourdough.
Proteins can also be classified in terms of their solubility. Globulins, enzymes and albumins are all water soluble, which means they disperse through the dough when you add water. Gluten proteins are not water soluble. They form a network of elastic that gives the bread the structure it needs to capture and hold air. The dough rheology – how strong and flexible the dough is – depends on the balance of the glutenins and gliadins within the plant, and it’s this which affects the structure of the dough and the crumb structure of the bread.
Understanding protein in flour
What many people who bake don’t have is a fundamental understanding of flour. Most people reading this will not have access to the kind of information that I have. I grew up with family who run one of the largest mills in Europe, so I’ve always had this exceptional understanding and incredible connection. It’s not essential to have this understanding, but knowing just a little about the way the proteins work can really help you to get the best out of any given flour.
One thing that does make it tricky for bakers is the way in which each country presents the percentage of gluten on the side of a bag of flour. This differs from one country to another, so it can be difficult to gauge just how the flour will behave when you bake with it. In Europe, you will often see the full protein content listed, inclusive of the albumins, globulins and enzymes. Whereas in the UK, when we talk about protein, we’re specifically referring to just the gluten. Consequently, if you’re choosing flour in Europe, it may look stronger from the numbers on the packet, but behave weaker.
In all my baking, I tend to blend flours to create the kind of dough rheology I want. This comes through an understanding of the balances of glutenins and gliadins. For example, an enriched dough that contains eggs, sugar and butter, needs a high protein flour – 15% or even 16% protein. The dough needs proper structure from a big, beefy high protein flour. For other breads, a high hydration ciabatta perhaps, a very strong flour might produce a very open crumb, but the loaf would be relatively tasteless and quite chewy. To achieve a balance of strength and flexibility with good flavour and texture, I blend higher protein flours with wholemeal, stoneground, spelt or heritage grains. And it’s a real joy to do that.
For cakes and pastries, strength doesn’t matter; in fact quite the opposite. For these, I use flours that have less structure. Using these flours on their own in a bread would perhaps create a loaf that has quite a nutty, flavoursome, delicious crumb but not much openness, because there isn’t the structure there. But the upside of using rye, barley, emmer, oats, einkorn, rivet, or Khorasan blended in bread, or in pastry and cakes, is that you get all the nutritional value of these grains, along with the texture and flavour. And this is one of the most delicious ways to play when it comes to working with heritage grains in sweet sourdough.
To get that lovely spring from our dough as it bakes, we need to develop the gluten. Here at the School, we mix rather than knead the bread, because in the very long, slow fermentation of the dough using a retarded method, the gluten will develop anyway. Given time, the glutenin and gliadin proteins will form the all-important bonds naturally, so the long, slow fermentation reduces the need to knead.
For cakes and the pastries we actually want quite the opposite. Instead of a chewy, open texture, we’re looking for light, crispy pastries, crumbly biscuits and cakes with a sweet, soft crumb. We can avoid developing the gluten in cakes and pastries by choosing a flour with a low protein content – something like spelt (which is one of my absolute favourites), rye, barley, oat flour or rice flour. The method for making a cake dough or pastry also helps limit gluten development. Rubbing in the butter coats the flour with fat and acts as a preventative measure to gluten developing. It’s also important when you’re making your cakes to use a light touch and keep mixing to a minimum.
For successful pastry, cold fingers are a must, and one of the biggest mistakes people make when working with pastry is rushing when rolling it out. It’s really important to allow the gluten to relax and not to overwork the dough. My advice when mixing cakes or when rolling out pastry is to wait for just a minute or two. This short pause gives the gluten time to relax and makes a big difference to your bake. Wait, then mix or roll out again and, if needed, give it time to relax for a minute more. This pattern of working the pastry and pausing is essential to get the texture we’re after. It’s especially important for pastry to have time to relax and chill. I often put my pastry in the fridge before I bake it so that it can relax before it goes in the oven. Otherwise you’re likely to get tough pastry – and no one likes tough pastry.