Milling – showing grain preparation and conditioning, and then milling to produce bran and flour fractions that are suitable for end use.
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The first stage of the milling process is cleaning the grain. This essentially means removal of all those parts of the overall grain sample which aren't the target wheat, this may include other seeds or other grains from other cereal types. Once the grain is cleaned the next stage of the process is conditioning, this is the addition of a fixed amount of water to grain which allows the subsequent milling process to take place more effectively. This occurs by ensuring that the bran is tougher and more easy to separate and the endosperm is softer, more friable and thus is easier to reduce down to the particle size of flour.
To allow conditioning to be undertaken effectively the grain moisture must first be determined and from this the amount of water that needs to be added to a fixed amount of grain can be calculated. Once this is done the water is added to the grain, the two are mixed together and then the grain is allowed to lie for a period of time, typically of the order of 16 to 24 hours for hard milling wheat that would be used for bread making. Within this time the changes occur which allow the bran and the endosperm to be separated most effectively and the endosperm to be ground down to generate the required properties in the final flour.
Once the condition grain is ready for milling and it is then transformed into flour through a series of grinding and sieving operations. The grain itself is fed progressively into the mill and there are a series of rolls which grind the wheat down to smaller particle sizes. In this case this is the break side of the milling passages, the break being essentially where the grain is broken up and the combined bran and chunks of endosperm are then sieved and a proportion of flour is released at this point as well as bran material which is which is released from the outer part of the grain. The endosperm chunks that are free from bran then go to the reduction side of the flour mill and within those passages the chunks of endosperm are broken down into the flour of the right particle size but also having the right functional characteristics to allow it to be used effectively for the desired baking use whether that be bread biscuits or cakes.