Mark Whitehead takes a scientific look at flour. He also considers some odds ‘n’ sods that are not used in Real Bread baking, but can be used in various combinations in industrial loaf production.
Let’s start off by saying what we mean by ‘flour’. It’s not just the 3lb (sorry, metrication police - 1.5 kilogramme) bags of white powder you get from the supermarket. Well, it is that, but it’s a lot more, too. Though virtually any cereal grains, and even dried potatoes, can be ground to give a type of flour, I’m going to concentrate on wheat flour, particularly bread flour. This is because flour in much of the West is usually ground cereal, and in the UK we generally expect these grains to be wheat.
Bread flour contains several different types of substances, which before the wheat seeds were milled would have been essential for them to grow.
The starch that makes up the bulk of a wheat grain is simply lots of glucose molecules joined together in long chains. Most of these chains branch a bit, making strands with bits hanging off them. There will be several thousand glucose molecules in a typical starch chain but they’re still so small you’d need a very powerful microscope to see them. Starch provides energy for the first stages of growth of a wheat plant, and in bread making it is broken down into sugars by natural enzymes in yeast, which then feeds on them.
Even before yeast comes on the scene, there’s usually some of one or more types of sugar in the flour. This is mostly glucose but perhaps also some sucrose - the sugar you get in a bag from the supermarket. Sugars should be only present in very minute quantities. More than this means that the starch is breaking down for some reason and is a sign that something is going wrong.
Proteins (there are many different types) are the ‘building blocks’ of all living organisms. Like starch, proteins are also long chains, but in this case they are made up of amino acids. In animals, they’re at their highest concentration in such bits as muscle and skin.
Plants also contain proteins. In the case of wheat the ones we’re most interested in fall into two groups: the glutenins (which are elastic or springy) and the gliadins (which are plastic or stretchy), which are found in different combinations and proportions in all wheats (such as spelt, emmer, einkorn, Kamut/khorasan and durum) and other cereals including rye and barley. These combine to form gluten – the stretchy stuff that traps carbon dioxide allowing the dough to rise. ‘Weak’ flour for cakes, biscuits etc. (e.g. plain and self-raising) will usually contain about 9-12% protein, whereas ‘strong’ (aka ‘bread’) flour comprises 12-15% or more. What some bakers are now realising, however, is that it’s not just the percentage of protein that’s important, but also its bread making quality, which is based on the types and relative ratios of the gliadins and glutenins that are present in each batch of flour.
There’s also some of the fibre we’re told we should eat more of. We need fibre to keep us ‘regular’ and generally contribute to good digestive health. It’s filling when we eat, and helps to maintain a healthy circulatory system.
Fibre is a complicated network of many, many glucose molecules arranged in such a way that they are not soluble (hence falling into a category known technically as non-soluble polysaccharides, or NSPs). This means that although fibre is filling, we can’t digest it and so it can’t contribute to weight gain. More simply put, this is cellulose, the material that gives plants their structure and that we use to make things like paper. In wholemeal flour, much of the fibre comes from bran, the outer layer of the grain.
In many a bag of flour, there will be other bits and pieces - some of which are even natural! By law all UK millers must add the following to all but bread flour except wholemeal, but don’t have to show them on the label.
Calcium carbonate aka chalk. This dates back to when our diets were very different to today. Today, almost all adults and children have enough calcium in their diets without our bread flour having added chalk. Adolescents are a bit worse, but they always are!
Iron is essential for blood cell formation, but the huge majority of people in the UK would get quite enough iron from their diet if adding it to bread ceased tomorrow. Again, adolescents (particularly girls) may need to be sure that they got enough from other sources, such as green vegetables.
The B vitamins thiamin and niacin are both amino acids vital for making muscle (and other) protein. Once more, virtually everyone would get enough of these even if they were not added to bread. If you don’t, then eat Marmite!*
In 2013, The Department for Environment Food and Rural Affairs (Defra) will be reviewing the need for these ‘fortificants’ and the efficacy of the forms in which they are added to flour. Defra will be putting the possibility of their removal out to public consultation next year. See the flour fortification page of the Campaign’s website for details.
Ascorbic acid (E300) is added to speed the cross-linking between gluten strands – basically to make the dough stretchy much more quickly than the combination of hydration (adding water) and kneading will. Though also known as vitamin C and found naturally in certain fruit and vegetables, it can also be produced as a food additive from glucose, sorbitol, sorbose, and 2-keto-gulonic acid by oxidation with hypochlorous acid in the presence of hydrous cobalt oxide catalyst. Nice. It is denatured by higher heat levels and the resulting residues are of no dietary benefit in baked products.
Extra enzymes can be added for a range of reasons, including ensuring a rapid conversion of starch to sugars to feed the yeast in the very short fermentation time in industrial baking. These may or may not be fully destroyed by baking, and Real Bread bakers seem to manage well enough without them. Many of these added enzymes can be deemed ‘processing aids’ and as such, though they would have to be listed on a bag of flour, would not have to appear on a loaf label.
As noted by John Letts in True Loaf issue 6, extra powdered, dried gluten (also known as ‘vital gluten’, though it is nothing of the sort) is sometimes added to weaker flours to make loaves rise better. As gluten is a component part of flour, EU law doesn’t consider any extra that is thrown in to be an additive and so doesn’t require it to be listed on the label.**
Great-sounding compounds including glycerol monostearate can be added to factory loaf dough to slow staling. In simplified terms, they stop the starch chains coming back together as quickly.
And then there’s calcium propionate (E282), which can be added to the dough or sprayed on a finished loaf to inhibit mould growth.
The list goes on, but for now, enjoy your Chorleywood ‘Bread’ Process loaf!
* Though watch those salt levels. Other brands of yeast-sludge-based savoury spreads are available [ed.]
** The only way to find out at present is to ask the miller. New EU country of origin labelling, however, may force millers that add gluten obtained from wheat grown in one country to be listed separately if added to flour milled from wheat grown in another. See the Food Information for Consumers Regulation section on the additives and labelling page of our website [ed.]
First published in True Loaf magazine issues 11 and 12, April and July 2012