Our most important task is selecting great grains for our flour and the blending of these different varieties to give precisely the right baking qualities. Milling great flour is not simply about crushing the grains into a powder. It is about separating the parts of a “berry” of grain into its constituent fractions. The best way to do this is through a shearing action where the white endosperm is literally scraped or sheared off the harder more fibrous bran.
The process of using stones to grind wheat into flour is an ancient tradition. The basic principle of a fixed “bed” stone and a rotating “runner” stone has changed very little in thousands of years. The Runner stone has an eye in the centre through which a controlled stream of grain is poured and the milled meal or flour travels out to the edge of the stones along grooves or furrows.
At Shipton Mill we have three pairs of stones that are used to produce a range of organic stoneground wholemeal flours. The secret is in the care of the stones, the setting of the stones during the milling process, the type of stone used and the “dressing” of the stones to keep them in the best condition for milling.
The stone itself is made from French Burr Stone, a type of very heavy marble that is hardwearing but at the same time has excellent heat transference properties. It is important that the heat is transferred away from the flour so that it is lightly warmed rather than toasted, as too much heat will cause excessive damage to the starch and reduce its baking qualities. The surfaces of the stones are cut so as to provide “lands”, which are the raised surfaces, and furrows, which are recessed grooves. The surface of the stones tapers towards the outside so that as the flour is milled it travels out along the furrows to the edge of the stones.
For a miller, it is important that the stones are kept in just the right profile and that the gap between the stones is as accurate as possible. Too big a gap or unbalanced stones will result in coarse or poorly ground flour, which will deliver poor results in baking and fetch a reduced price. It was the task of the “Millwright”, typically a travelling craftsman, to correctly “dress” the stones using a “mill bill” or large beak shaped hammer, with which the stones were carefully chipped away to ensure that they meshed together at just the right setting and rotated evenly and in a balanced manner.
A millwright’s experience would be determined by the miller asking to be shown the “metal” he was made of, at which point the millwright would roll up his sleeves to reveal forearms studded with black specs – chips of stone and metal from the mill bill that fly off and embed in the forearm; the more extensive the forearm speckling the more experienced the millwright. Now modern techniques can be used to ensure that the stones are dressed properly and there are very few, if any, qualified travelling millwrights left. We are one of the last remaining millwrights able to make and dress our own stones.
Stone-milling means all the grains are ground in one process, all their goodness is retained, and the whole stoneground grain imparts a lovely nutty flavour to the flour, with great texture.
As populations grew and the demand for more and better flour and bread grew, so a new milling process was devised. Originating in Hungary in the late 1870’s, this new process involved passing the grain between sets of spinning metal rollers or “rolls”. Initially the first roller mills were just using this process to break up the grain before then finishing the process between traditional stones.
Gradually, the process was refined so a succession of rollers and sieves could be used to remove all the bran and wheat germ from the grain through a staged milling process or "reduction" with each consecutive set of rolls making the flour finer. The first set of rolls in a mill is called a “break” or "break rolls" and subsequent rolls are referred to as “reductions rolls”. By increasing the number of rolls and with other advances in milling technology affording better separation techniques, almost all the bran could be separated out to produce super-fine white flour. The complex system of breaks with fluted rollers and then a series of coarse to smooth reduction rolls shear off the white endosperm from the bran and gradually reduce the particle size.
The first “break” splits the berry in to two or three parts and starts the shearing process, removing the white endosperm from the bran. The “middlings” (small fragments of grain) are “bolted” or sieved to remove the bran. The middlings are then reground at the second and subsequent breaks using a slower grinding speed followed by more sieving, and so on. To produce wholemeal flour from this type of milling it is necessary to collect all the “brown” particles that have been removed during the sieving processes and add them back to the final product. A "brown" flour is one where only a certain proportion and type of the extracted material is added back.
Not only are roller mills faster, they produce more white flour of a higher quality than was ever able to be extracted from stone milling and sieving. In the late 1800s, white flour was considered refined and fashionable, whereas course and gritty flour was thought unsophisticated and rural. However because of their higher speeds and more vigorous action there is a lot more damage done to the components of the flour. There are ways to reduce the damage and maintain a greater level of natural nutrients and milling technology is evolving to reduce the pressures and temperatures within the rolls.