- Durum Flour Milling Process –
Flour Mill Home - Durum Flour Milling Process
Upon arrival at the mill a wheat sample is taken to the mill's laboratory where it is checked for Protein, Moisture, Test Weight, Ash and falling numbers. Canadian Durum Wheat is the cleanest in the world, however after arriving at the mill it has to be cleaned extensively, to remove as many of the impuritites as possible, some of which are picked up in grain handling systems. These impurities consist of coarse grain, corn, soybeans, white beans, stones, wild oats, barley, and weed seeds.
Once wheat is cleaned, water is added and allowed to sit, or temper, in bins for eight hours. This allows for easy separation of endosperm from bran. Endosperm is the inner part of wheat kernel containing Semolina and flour. Bran is the outer layers of the wheat kernel. Tempering helps bran become sufficiently tough to avoid being unduly broken up. The wheat then goes through a debranning process, which removes high percentage of bran from endosperm. This 2 step process, consisting of the abrasive and friction sections, requires large amounts of air for conveying and drying.
The wheat then goes to the mill. The mill involves an extensive system of light grinding, sifting and purifying to produce semolina of proper clarity and particle size. Wheat is weighed as it is transferred into the mill. It passes through a set of corrugated rolls. For pasta, durum is milled into coarse chunks of semolina therefore rolls are set to release coarse chunks of endosperm and minimal amounts of flour. It is then lifted pneumatically to top of mill and then comes down through sifters.
A Plansifter may have 4 or 6 sections with each section containing 20 - 27 sieves. The driving mechanism is located in the centre and the sifter is suspended by groups of canes. As the product comes down through the sieve it is graded by size into 4 or 5 different streams that either go to a purifier, back to a different rollermill for further grinding, or flour which is also removed by sifting. Sieves are in 2 pieces, a frame and a stainless steel woven cloth ranging in weave from 18 to 135 per inch.
The purifier is a machine with two sections, each section consists of oscillating layers of sieves. These layers of sieves are held in a metal frame. The frame is suspended, sloping slightly downward from the front to the tail end. This slope facilitates the gradual flow of material from the front to tail end of the machine. Controlled air currents drawn through the flow of material then stratify the stock layers so the heavier endosperm particles fall through, while lighter branny materials float on top to tail end where they are discharged to feed or further grinding. The endosperm particles go to semolina if proper size or go to rollermill to be ground finer.
This grinding, sifting, purifying process is repeated several times until as much semolina can be extracted as possible. Semolina is combined from different purifier streams of different granulation that must meet customer specification, it then passes through a rebolt sifter, scales, and if required, vitamin enrichment is added. It then is conveyed to storage bin.
From storage bins it is transferred to bulk trucks, or packer bin for packaging into 40 kilogram paper bags, or 750 kilogram tote bags.
The quality of finished products must conform to the requirements of the end user. To ensure the customer receives quality products consistently, a quality control program is adhered to for all production. Products are constantly being tested and analyzed for Moisture, Protein, Granulation (range of particle size), Ash and Speck Count (measures level of purity), Falling Numbers (indicated Enzyme activity). Samples are sent to outside laboratories for enrichment assays and microbiological testing.
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