In times gone by flour was made by grinding wheat between two stones – one static and the other turning. This simple process crushes the wheat and mixes all the component parts together. This crushing method makes it difficult to separate the white flour. Roller mills shear the grain open which makes it easier to scrape the endosperm away from the wheat bran and wheat germ to produce white flour.
A small amount of the flour produced today is via the stoneground method (less than 1% of total production). The nutritional value of flour is determined by whether it is white, wholemeal or brown and is not affected by the method of milling. Stoneground and roller milled flour are equally nutritious.
Explanation:The wheat grain
Like most natural plants and fruits, grains, including wheat grains, consist of three main components. Think of an avocado. Firstly there’s the protective outer layer – the skin – which in wheat is called bran. Then there’s the seed from which the new plant grows. In the avocado this is the big stone, and in the wheat seed it is called wheat germ. Finally, there’s the main food source – in the avocado it’s the green flesh and in the wheat seed it’s the starchy endosperm. The endosperm is essentially just white flour sitting inside a wheat seed waiting to be removed.
How flour is made: in detail
Not all flour is equal. Just as there are different varieties of apples or potatoes, each variety has unique properties and characteristics. These make it more or less suitable for certain products. So some flours are best for making light, airy breads; others for making cakes or biscuits; and others still for making pizza.
So farmers grow different varieties of wheat that will produce flour with different properties so that the baker can purchase the most suitable flour for the products their customers want to buy.
Delivery and storage of grain
When wheat arrives at the mill, it is tested to make sure that it has the required specification to make the right flour for the baker – or other customers’ – needs. It is tested against a contract specification for variety, moisture content, specific weight, impurities, enzyme activity associated with sprouting, protein content and quality. It passes through a preliminary cleaning process to remove coarse impurities, such as nails and stones, and may be dried before being stored in silos according to quality.
Assessing the wheat quality
The ‘Hagberg Falling Number’ measures the time, in seconds, a plunger takes to descend through a heated mixture of ground grain and water. The test indicates the alpha-amylase activity in the grain. This natural enzyme converts starch to smaller sugar units that would be used by the seed to fuel its growth.
If there is little enzyme activity, the mixture will remain viscous. The plunger will take a long time to descend and a high Hagberg Falling Number will be recorded. Too much enzyme activity and the reverse will be true. High enzyme activity impairs bread quality, producing a very weak and sticky crumb mixture.
Cleaning and conditioning
When wheat is drawn from the silos prior to milling, it is thoroughly cleaned. Powerful magnets extract any remaining ferrous metal objects.
Machines, which separate by shape, remove barley, oats and small seeds. Gravity separation removes stones and, throughout the cleaning process, air currents lift off dust and chaff.
The wheat is then conditioned to a suitable moisture content by tempering it with water and leaving it in conditioning bins for up to 24 hours. This conditioning softens the bran and enhances the release of the inner white endosperm during milling.
Blending
Cleaned and conditioned wheat is then blended in a process known as gristing. This combines different wheats to produce a mix capable of making the required quality of flour to suit the needs of the flour millers’ customers.
