Grain Cleaning Process Prior to Grinding

13 September 20168 min reading

"Combined elements of grease, humidity and organic/non-organic residues will shortly result heating, escalation, burning and vermination. Such problems will reduce the wheat quality significantly, causing damage to the business."

Ömer Şerif GÜLTAY Plant Conservation Department, Faculty of Agriculture, Tokat Osman Gazi University filistinThe wheat is subjected to a precise and rigorous cleaning process of three stages prior to grinding process at flour factories, in order to eliminate waste and foreign bodies. Wheat cleaning prior to grinding can be categorized under three headings as follows: 1. Preliminary Cleaning, Classification and Storage; 2. Final Cleaning, Blending and Conditioning; 3. Preparation Prior to Grinding

1. PRELIMINARY CLEANING In case of failure to perform an effective and detailed fight against weed on wheat fields, weed seeds (mustard, vicia sativa, wild oat, Italian rye, corn cockle, goatgrass, coontail, cheat grass, coralroot, cephalaria syriaca and elymus) as well as their stems, hay and waste are mixed with wheat. Moreover, if the humidity of the air is high when harvesting the wheat or if it is harvested early in the morning, it is inevitable that the harvested wheat will contain hay, waste and husk at amounts many times more the required amount as the combine harvester will fail to separate the wheat from its ear completely due to dew, or hoarfrost, formed at night. Both weed seeds and their husks, hay and waste and the husk, hay and waste in the wheat as well as wheatworms like eurygaster, and even insects and insect residues including grasshoppers and snails must be wiped out before storing wheat in silos.

Why is it important to perform an excellent and precise preliminary cleaning? The high oil and humidity content of such weed seeds and the highly humid husks, hays and waste of such seeds as well as the high humidity content of hay, waste and husk of wheat pose a danger for the wheat. It is very likely that the organic/non-organic insect residues carried into the crop from the fields by the combine harvester will come together and form clusters inside the silo when transferring the wheat into silos. Combined elements of grease, humidity and organic/non-organic residues will shortly result heating, escalation, burning and vermination such problems will reduce the wheat quality significantly, causing damage to the business.

Another important aspect is that when the wheat not subjected to good preliminary cleaning is being taken from the silos to be processed, such foreign bodies will cause obstruction in wet scales and blending equipment, resulting in serious fluctuations in production spectra. Production spectra will vary since the fluidity of the wheat will be different depending on whether it has undergone a good or poor preliminary cleaning process.

The main equipment used for preliminary cleaning is waste purifier. The waste purifier comes with several models. Recently, the machine manufacturers developed highcapacity combined models and offered them to the service of our industry. For some reason, both the machine manufacturers and operators have given priority to capacity in preliminary cleaning machines. Therefore, cleaning and grain loss were pushed in the background. However, we would expect and continue to expect from machine manufacturers the following: "commitment and warranty for a preliminary cleaning with zero grain loss and maximum 0.3 to 0.5 foreign bodies..." If machine manufacturers highlight cleaning and grain loss by pushing capacity in the background, we could handle elimination of foreign materials from wheat right at the beginning of the process which the preliminary process. You can be confident about that.

Maximum grain loss of 0.5% represents a serious figure for a business processing an annual amount of 100,000 wheat. Unfortunately, the finest quality and fertile grains are lost particularly in the waste purifier as well as other equipment in the cleaning group. We must act consciously by considering the impact of such loss on the business and national income. 2. FINAL CLEANING, BLENDING AND CONDITIONING Wheat that is classified after the preliminary cleaning and stored by its type, color, humidity and spectrum values, is taken from the silos through blending based on the purpose of production to be transferred to the process for detailed cleaning. Wheat is then subjected to a detailed cleaning and conditioning process by passing through 10 separate machines in the cleaning and conditioning group. Main machines within the cleaning group are as follows: 1. Dry peeler 2. Waste purifier 3. Classifying destoner (combined separator) 4. Trieur (seed and barley trieur) 5. Color-sensitive cleaning equipment SORTEKS or equivalent 6. Condensing forced heating equipment 7. Transfer forced heating equipment 8. Elevators-spiral screws 9. Aspirators 10. Aspiration and filter system

Wheat is first run through the dry peeler or any equivalent equipment to ensure the grains hidden in the husk are removed. At the same time, the wheat is compressed to special peeler strings by using conveyor pallets to be cleaned by rasping. Then it is run through the waste purifier with sensitive cleaning capability to remove stems, hay, husk, small hayseeds and thin, broken and tiny grains. Then it passes through the classifying destoner (combined separator) in order to sort stones, metal, glass, waste and weed seeds which are heavier or lighter than wheat. Optionally, this machine can be used to classify wheat by separating poor and mealy grains with high starch content. Classification may be required for special-purpose production.

Afterwards, the wheat is run through the trieurs in order to remove round hayseeds, broken grains and barley, rye and wild oat grass in the wheat. In case required prior to wheat conditioning, it can be classified by means of a SORTEKS or any equivalent classification machine with color sensitive cleaning feature to be sent to the condensing forced heating machine in order to be conditioned. In a way to ensure 14.5 humidity for the flour to be produced, the half of the calculated amount of water is given through the condensing forced heating machine for initial tempering. After initial tempering, the wheat is left to rest in conditioning silos from 12 to 24 hours before the transfer. The wheat to be transferred is added water remaining in the transfer forced heating machine and then the wheat is left to rest in the transfer silo. Hard and semi-hard wheat with low humidity is conditioned, if deemed necessary, without heating the wheat, by performing the second transfer. After leaving to rest for a sufficient period, the wheat is sent to the preparation process prior to grinding in order to be ground by blending again, if deemed necessary depending on the purpose of the flour to be produced.

Why is final cleaning important? Bread and other bakery products which are consumed every day by humans, usually multiple times a day, as a nutrition source must be produced by considering the human and public health. The wheat may be contaminated by biological and chemical materials during harvest or storage and handling after harvest. Chemical pesticides are started to be used at the very beginning when the wheat is inside its ear, containing toxins for pests. When harvesting the wheat, it is stored temporarily by transferring with trucks and tractor trailers. Neither transportation vehicles nor temporary warehouses are suitable in terms of hygiene and sanitation rules. These transportation vehicles are used to carry chemical fertilizers as well as any type of packaged or bulk cargo. It is not known if such materials transported pose a threat for human health and temporary warehouses are built for general purposes.

These warehouses can be used to store fertilizer, diesel oil, disinfected seeds and similar goods. Toxic chemical pesticides are also used in these warehouses against pests and rodents. Only if a final cleaning is performed by fully observing the hygiene and sanitation rules, such problems closely concerning the human and public health can be eliminated. Machinery used for final cleaning sorts out and cleans biological and chemical materials that might be contaminant. Especially the goods with specific gravity that is different from wheat, which are either heavier or lighter than the wheat, are sorted out by sieving and air aspiration, while undesired goods with the same weight and size with wheat are sorted out, or even classified, by using the state-of-the-art SORTEKS and other equivalent machinery which operates sensitive to color.

3. PREPARATION PRIOR TO GRINDING Wheat that is cleaned and rendered ready for grinding after conditioning is first run through the scrubbing machine and any equivalent equipment during the preparation process. Finally, prior to the B1 warehouse, it passes through the preparation waste purifier as the final control before grinding to be sent to the B1 roll warehouse, the first crushing mill, in order to be milled.

Wheat harvest and especially its transportation must be put under the microscope considering the human and public health. Special grain transportation vehicles must be encouraged. Trainings and seminars must be organized to explain that no toxic materials must be present in the temporary or permanent warehoused in order to avoid harm to human and public health. Buy ensuring governmental support to flour factories, use of new generation cleaning materials, including mainly SORTEKS, must be promoted and encouraged.

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