To produce the highest quality flour, the aim of the miller is to identify and source the most suitable grain and properly prepare it for milling, and then to separate as much good quality flour as possible from the grain without excessively damaging the constituents of the grain, being the endosperm and germ in the heart of the grain, and the branny outer layers of the grain.
The endosperm is a crystalline matrix of complex carbohydrate and protein, which, when progressively reduced in particle size, is reduced from chunks of semolina into fine particles of flour.
The wheat grain has a natural crease where branny layers are trapped within the endosperm, and this prevents a perfect separation of bran and germ from the endosperm.
Milling to produce white flour removes most of the bran layers and the germ, which together amount to about 15% of the wheat grain. This means that, depending on the milling technique, not all the bran can be separated, and up to 50% of the germ is retained in the white flour.
Milling is now much more than the simple Grinding of grain. The following description will give you an understanding of the processes of milling of grain as we perform it.
There are thousands of varieties of wheat, and each has adapted to its environment. Plant diseases are constantly evolving, and compromising the agronomic viability of existing varieties. Plant breeders are constantly finding and sourcing new parents from around the world, and assessing the quality and agronomic viability of both parents and their offspring as they seek to improve both grain yield for farmers and baked product quality for consumers.
METLwork with all Tanzanian plant breeders to provide guidance as to desired outcomes and assist with practically achieving improvement, and work with individual farmers to produce grain of targeted processing characteristics.
Grain, like grapes, is a seasonally grown crop that is harvested annually, and which varies in quality according to the genetically conferred attributes of the grain, the intrinsic nature of the soil and region, and seasonal effects on the growing environment. Thus, while the potential processing quality of every grain Variety is considerably different, the environmental effects can be even greater and will ensure quite remarkable differences even if the grain is of the same variety. For example, a wheat variety that is useful for making shortbread biscuits will be totally unsuitable for making flaky pastry. And, too much rain during the growing season can make a bread-making variety unsuitable for intended purpose, while too little rain will similarly affect a biscuit-making variety.
Grain, when reaped, is therefore typically separated within Segregations by variety and region and environmental effects for the purpose of selection by Millers for making different types of flours.
METLwork closely with farmers and grain handlers to ensure that the most appropriate quality grains are reliably available, and Laucke’s greatest physical asset is its large number of on-site grain storage segregations.
With the Genetics by Environment complexity, every single grain offers different end product potential. Laucke evaluate the existing and potential quality of every parcel of grain and indeed every ingredient before sourcing it; before receiving it; and before, during and after processing it at every stage of processing. We also produce from every batch in our test bakeries the intended range of end products so as to assure ourselves that our product has the capability of meeting or exceeding consumer expectations.
Farmers clean the grain as they reap it. Millers clean the grain as they receive it, and again clean the grain before they mill it. Mill cleaning is an intensive and multi step process, intended to remove any foreign or unsuitable seeds, unmillable material and physical contaminants.
Water and Time are utilised to progressively condition or temper the grain, where we seek to make the branny outer layers of the grain more flexible and readily separable from the endosperm, and seek to modify the crystalline matrix that binds the endosperm such that the complex carbohydrate provides the intended rate of water absorption and rate of fermentation when utilised as flour within a dough.
Effective grain conditioning is essential to create high quality flour, and METLutilise a highly controlled and sophisticated two stage process of grain tempering.
This is what was, in earlier times, the first and only stage of the milling process.
Grain is progressively passed through a series of several individually fluted “Break” grinding surfaces (either Roller grinding or Stone grinding) with different grinding gaps, where the grain is broken open and the adhering endosperm scraped off the branny layers.
The endosperm may be ground finely enough to approximate fine flour if the grinding gap is reduced and enough grinding pressure is applied as with a traditional stone grinder.
With “modern” milling, after every grinding passage, the stock (ground / sifted product) is sifted and graded so as to then stream the most suitable stock to the next grinding passage.
After each Break grinding passage, the stock is sifted by particle size separation over a variety and number of sieves into several streams containing branny flakes with degrees of adhering endosperm and germ, and several streams of various sized of chunks of endosperm with degrees of similar sized particles of germ and bran. The former are sent to subsequent break rolls, the latter sent to appropriate Purifiers.
Endosperm chunks with adhering or an admixture of bran flakes and germ can be differentiated by density. Carefully regulated air currents, in combination with oscillation, stratify the stock so that sifting can progressively remove the purest semolinas from the contaminating bran flakes.
Effective purification is essential to create high quality semolina and white flour, and while purification as a process is not routinely used by all flour millers, METLutilise a highly controlled and sophisticated multistage process of sizing and grading to ensure highly efficient purification of its specialist white flours and semolinas.
After sifting and purification, each group of various sized chunks of endosperm are sent to different roller mills to be reduced in particle size. Grinding gap and pressure are carefully regulated so as to protect the integrity of the grain quality, but also to create the required fermentation characteristics of the intended dough.
By progressive grinding over a series of reduction rolls and sifting to sort the ground product after each grind, semolina is progressively reduced in particle size until it becomes fine flour.
After each Reduction grinding passage, the product is sifted into many streams which may be classified as 3 notional groups – those which will be carefully reground to further reduce the particle size, those that are already small enough in particle size and suitability to be classed as flour, and those that should be classed as by-product due to quality considerations. The “head” sets of several reduction rolls produce mainly smaller chunks of semolina intended to be ground again, the “middle” sets of reduction rolls seek to produce a high proportion of fine flour from even smaller chunks of semolina, and the “tail” sets of reduction rolls produce a rapidly diminishing amount of high quality flour and correspondingly more by-product that is deemed unsuitable to be a fine flour.
Flour Mills are very complex beasties. They are very sensitive to changes in heat and humidity, and take some time to settle down and adjust after startup and after any change. It is best to run them continuously, 24 hours per day. Laucke Flour Mills’ reputation for quality stems in part from its attention to detail with Mill process flow, systems, setup and adjustment, and the choices made regarding questionable quality flour streams.
To enable the operation of the dozens if not hundreds of individual machines involved with the major milling processes described above, there are a further multiplicity of other machines that provide complementary services such as conveying stock; supplementary grinding and sifting services, filtering and exhausting and compressing and cooling the air used for conveying and power, blending and mixing and storage of raw materials and finished product (flour should be aged like wine!) not to mention the multiplicity of command and control systems that are used to ensure that it all works! A properly equipped mill will utilise many hundreds if not thousands of devices set up so as to reliably process Good Grain into Great Flour.
Over thousands of years, people have milled grain using a variety of means and power sources, using their own strength, animals, wind and water to power a variety of grinders.
The hand operated saddle stones used by the Egyptians were supplanted by Roman querns, which were still used in Europe in the 1800s. Hand stones and Querns were progressively replaced over two thousand years as other forms of motive power supplanted human muscle.
Water-powered mills date back to early in the Christian era, while windmills first appeared in Europe around 1300 and were widely used until the invention of the steam engine in 1751 provided a more efficient power source.
As improvements in technology enabled more efficient power sources, so too did such improvements allow the development of more efficient grinding and sifting.
The development of practically effective metal Roller Grinding machinery in Hungary during the 19th century revolutionised the milling industry by improving the miller’s ability to reliably and efficiently produce high quality, high value white flour whilst removing a source of contamination, and improving nutrition and shelf life. This was enabled by the ability to selectively control grinding, and then be able to sift and grind again in a controlled and progressive manner without uncontrolled damage to the endosperm and the germ.
In effect, roller grinding enables grain to be relatively gently and progressively “teased” apart by multiple choices of cutting and grinding, where every pair of rollers have a different setup with a different surface, controlled grinding gap, and varying pressure and friction that either slices the branny layers and scrapes off the endosperm, or shears apart the various constituents of the grain with minimal disruption. Once each constituent is separated, they are then able to be individually processed as appropriate whilst maintaining their food value integrity.
Consequent to every individual processing stage some components of the grain may be liberated as flour, or may continue through some or many more grinding and sieving passages. By sifting consequent to the first pass of grinding, some flour may be liberated within just a few seconds, and more will be liberated at every sifting stage after every subsequent grinding passage. It may take up to an hour for some stock to pass through the multiplicity of grinding stages.
All streams, once ground and sifted and separated as appropriate to intended function and end product, have their products grouped to become either the value-added flours we are seeking, or by-product.
This system of roller grinding, developed in Hungary 150 years ago, is still in use today, and has led to the evolution of a complementary overall sophisticated system of milling that is still evolving.
Early methods of stone grinding involved the simple practice of crushing grain between two stones, roughly grinding it to form a ‘meal’. The Romans refined this process by utilising the quern, an arrangement of two millstones with the upper one being turned by muscle power – either of a slave or an animal such as an ox. After crushing between the two stones, the coarse meal would be sifted through cotton or horsehair sieves to produce different grades of flour. The most highly prized flour was the very finest powdered white flour, so even then people were producing and grading flours from finest white all the way through to wholemeal.
Stone grinding gradually evolved over two thousand years to become more efficient. The action went from reciprocating to rotary, the motive power changed from muscle to water to wind and then to combustion engines, and the grinding stones became larger (up to 2 m in diameter) and obviously significantly heavier (10 to 15 tonnes each pair) and which were then comprised of multiple stones shaped, fitted and banded together.
Such stones are necessarily mounted horizontally where the lower Bedstone lies flat on the floor and the upper Runner stone is placed atop and is driven by a vertical shaft.
Grain is fed into the recessed centres of the pair of grinding stones. The runner stone rotates, while the bedstone remains stationary. One or both are furrowed with a series of grooves which distribute the grains outwards over the whole face of the stones. Grain is fed through a hole in the centre of the runner stone, and is gradually and progressively ground until the product spills out from the periphery of the stones and is collected for bagging or sifting.
With this traditional arrangement, and in conflict with simple intuition and popular representation, a traditional stone mill grinds unevenly and harshly in comparison to a roller grinder, cannot effectively grind properly tempered grain, and creates and retains heat in the ground product. This damages the endosperm, overheats the germ and destroys nutrients; reducing potential baking performance and keeping quality and nutritional benefits. Further, flour mills equipped with such horizontal stones often exploded (flour dust is more combustibly energetic than petrol) or burned down because the flour became so hot consequent to heat entrapped during grinding that the flour spontaneously ignited when it was released from the grinding stones and was exposed to air. Unhappily, too, such stone ground flour necessarily contained a proportion of stone grit. However, nostalgia abounds for elements of our heritage that have been lost, and there inevitably remains a degree of nostalgia associated with the traditional stone grinding milling process.
Stone grinding by its very nature does impart some unique characteristics to the ground product, and these characteristics also influence the baking process and may also create a differentiated final baked product. For example, stone milled flour inevitably includes as small particles more of the germ and the aleurone layer and the branny layers, and the endosperm chunks are larger and more uneven. Provided grinding pressure and heat are able to be controlled and the flour is fresh, it is possible to create a nutritious, enzyme-rich and high-ash flour or fine wholemeal for use by specialist bakers.
Therefore, we have installed new stone grinders so that we may (again) produce stoneground flours.
To optimise the benefits of and minimise the inherent weaknesses of traditional stone grinding, we have installed modern stone grinding machines with a superior configuration and better grinding surfaces. The stones of these new grinders are mounted vertically and driven by a horizontal shaft, which allows the effective use of tempered grain, allows more effective grinding control, allows more efficient passage of ground stock through the stones, and cooler milling. The grinding stones are now no longer natural stone which produce stone grit, but are of composite stone material with a regulated degree of porosity and abrasive roughness which do not have the same propensity to release grit.
Additionally and very importantly, these stone grinders are integrated with our existing sophisticated and complementary milling equipment, methods and systems. Instead of a single pass of poorly prepared grain through a pair of stones as with traditional stone milling, we employ all our other complementary and supplementary milling processes, ensuring that the Best grains can make Great flour, whatever grinding process is employed.
Therefore, while stone grinding has changed very little in a thousand years, it continues to evolve, and still has a part to play in the milling of grain based on consumer preference.