Overview
Also known as corn starch. Commonly known as six grain flour. White slightly yellowish powder. Made by impregnating corn with 0.3% sulfurous acid, through crushing, sieving, precipitation, drying, grinding and other processes. The common product contains a small amount of fat and protein, etc.. It is highly hygroscopic, and can reach a maximum of 30% or more. For properties and uses, see starch.
Methods of production
1. Cleaning
Cleaning corn contains a variety of dust mustard, organic and inorganic impurities. In order to ensure safe production and product quality, the impurities present in the corn must be cleaned. Methods of cleaning up corn, the main use of screening, wind selection and so on. Cleaning equipment are vibrating screen, specific gravity to stone machine, permanent magnetic drum and wheat washing machine.
Vibrating screen is used to remove large, medium and small debris in corn. The sieve is equipped with, the first layer of the sieve with a diameter of 17 to 20 mm round holes, the second layer of the sieve with a diameter of 12 to 15 mm round holes to remove large and medium debris, the third layer of the sieve selected diameter 2 mm round holes to remove small debris.
Specific gravity de-stoning machine is used to remove the corn in the juxtaposition of stone. Due to the larger size of corn, flat grain size, specific gravity is also larger and other characteristics, in the operation of the wind volume should be appropriately increased, the wind speed is appropriately increased, through the fishscale holes in the wind speed of about 14 meters / second. The raised height of the fish scale hole should also be increased to 2 mm, the operation should pay attention to the movement of the material on the fish scale screen surface, adjust the wind volume, and regularly check the discharge of stone discharge.
Permanent magnetic drum is used to remove magnetic metal impurities in corn, should be placed in front of the corn ground into the crusher, to prevent metal impurities into the crusher.
The wheat washer can clean the dirt and dust from the corn. The ash content of corn can be reduced by 0.02 to 0.6% after cleaning.
2. Soaking
Corn soaking methods are now commonly used metal tanks several or dozens of pipe connections combined, with a pump to make the soaking water in the tanks circulating between the flow, countercurrent soaking.
Dissolved in the soaking water with soaking agent by the results of the trial showed that lime water, sodium hydroxide and sodium bisulfite are less effective than sulfur dioxide, sulfur dioxide content should not be too high. Because of sulfur dioxide-containing soaking water on the protein network dispersion effect is enhanced with the increase in sulfur dioxide content. When the sulfur dioxide concentration of 0.2%, the protein network dispersion effect is appropriate, the starch is easier to separate; and the concentration of 0.1%, can not occur enough dispersion effect, starch separation difficulties. The general maximum does not exceed 0.4%, because the concentration of sulfur dioxide is too high, too acidic, the corn soaking and not much good, on the contrary, will inhibit lactic acid fermentation and reduce starch viscosity.
The soaking temperature has an important effect on the soaking effect of sulfur dioxide, improve the soaking water temperature, can promote the soaking effect of sulfur dioxide. But the temperature is too high, will make the starch paste, resulting in adverse consequences. Generally 50 ~ 55 ℃ is appropriate, not to make the starch particles produce paste phenomenon.
The soaking time is also closely related to the soaking effect. In the soaking process, soaking water is not from the corn grains of the epidermis of the various parts of the penetration of the internal tissue, but from the bottom of the grains of the root width of the loose tissue into the grains, through the bran layer of porous tissue penetration into the grains of the interior, so it is necessary to ensure that sufficient soaking time. After soaking corn at 50°C for 4 hours, the germ portion absorbs the maximum amount of water, and after 8 hours, the embryo portion also absorbs the maximum amount of water. At this time the corn kernels become soft and after coarse crushing, the germ and bran can be separated. However, the protein network has not yet been dispersed and destroyed, and the starch granules can not yet be free. If you continue to soak, can make the protein network dispersion. After soaking for about 24 hours, the protein network of the soft embryo is basically dispersed, and after about 36 hours, the protein network of the hard embryo is also dispersed. Because the process of protein network dispersion is to expand first, then turn into fine spherical protein particles, and finally the network organization is destroyed. So it takes more than 48 hours of soaking time to make the protein network completely dispersed.
The soaking conditions of corn in factories around the world are not exactly the same. General operating conditions are as follows: soaking water sulfur dioxide concentration of 0.15 ~ 0.2%, pH value of 3.5. In the soaking process, sulfur dioxide is absorbed by the corn, the concentration is gradually reduced, the most of the released soaking water containing sulfur dioxide concentration of about 0.01 ~ 0.02%, pH value of 3.9 ~ 4.1; soaking water temperature of 50 ~ 55 ° C; soaking time for 40 ~ 60 hours. Soaking conditions should be decided according to the quality of corn. Usually is stored for a longer period of time old corn with low moisture content and hard corn are required to be stronger soaking conditions, that is, require a higher concentration of sulfur dioxide, temperature and longer soaking time.
Corn after soaking, moisture content should be 40% or more.
3. corn coarse crushing
The purpose of coarse crushing is mainly to break the soaked corn into more than 10 small pieces in order to separate the germ.
Most of the corn coarse crushing disk crusher. Coarse crushing can be divided into two times. The first time the corn is broken into 4 to 6 pieces for germ separation; the second time it is broken again into more than 10 pieces, so that the germ is all off, and the second germ separation is carried out.
4. Germ separation
At present, domestic germ separation mainly uses germ separation tank. The advantage is that the operation is more stable, the disadvantage is that it occupies a large area, consumes much steel, and the separation efficiency is low, generally not more than 85%.
There are also domestic and foreign corn starch factories that use spin liquid separator. This separator is made of nylon, with 12 separators centrally placed on a shelf, the total length of not more than 1 meter, covers an area of small, large production capacity, high separation efficiency, up to 95% or more.
5. Corn grinding
After separating the germ after the corn crumbles and some of the starch mixture, in order to extract starch, must be ground, destroy the corn cell cells, free starch particles, so that the fiber and bran separate.
The good or bad grinding operation has a great impact on the extraction of starch. Grinding is too coarse, starch can not be fully free, because of the coarse and fine slag to take away, affecting the starch out of the degree. Too fine, fiber separation is not good, affecting the quality of starch.
In order to effectively grind corn, usually using the second grinding. The first time with a hammer crusher for grinding, after sieving starch milk; the second time with a sand disk starch mill for grinding. Some use the universal mill for the first grinding, after sieving starch milk, and then use the stone mill for the second grinding.
According to the production practice around the world proved that: the diamond mill is better than the stone mill, high hardness, grinding pattern is not easy to wear, the grinding surface does not require frequent maintenance, grinding efficiency is also high. Now gradually to diamond grinding instead of stone grinding.
6. starch screening
Corn fragments after grinding, to get corn paste, can be used to sieve the starch and coarse and fine residue separation. Commonly used sieving equipment are hexagonal sieve, flat shaking sieve, curved sieve and centrifugal sieve and so on.
The sieve holes for sieving starch should be decided according to the type of sieving equipment and starch quality requirements. Hexagonal sieve cleaning coarse slag sieve diameter of 0.6 mm, fine slag sieve diameter of 0.12 mm, flat shaking sieve sieve coarse slag sieve with 7 × × No. double material nylon, sieve fine slag sieve with 12 × × No. double material nylon, curved sieve cleaning coarse and fine slag using six-stage 120 ° curved sieve, the sieve length of 1.6 meters, the first level of curved sieve sieve seam width 0.05 mm, the rest of the levels of the sieve seam width of 0.075 mm; centrifugal sieve rotor sieve plate sieve hole is 2 x 0.24 mm. Generally with four levels of continuous operation.
Screening coarse and fine slag need to clear the amount of water, according to 100 kg of dry matter, screening coarse slag needs 230 ~ 250 liters, fine slag needs 10 ~ 130 liters, water temperature of 45 ~ 55 ℃, containing 0.05% sulfur dioxide, pH about 4.3 ~ 4.5 is appropriate.
7. Protein separation and starch cleaning
Separation of coarse and fine dregs of the starch milk concentration of 6 to 8 degrees boe, containing about 11 to 14% of the dry matter. The chemical composition of starch here is analyzed in the following table:
Components Content (%) Components Content (%)
Starch 88～92 Water-soluble matter 2.5～4.5
Protein 6～10 Sulfur dioxide 0.035～0.045
Fat 0.5～10 Fine residue 0.05～0.1 g/l
Ash content 0.2～0.4
From the above table, it can be seen that the dry matter in the starch milk is mainly protein and water-soluble matter except starch, so protein separation and starch cleaning must be carried out.
Separation of proteins is generally used in the flow tank separation, due to the large area, separation efficiency is low, and now gradually changed to centrifuge separation. However, the starch milk is required to contain less slag to prevent nozzle clogging in the disk, resulting in mechanical vibration.
Separation of protein after the crude starch milk must be cleaned. Most of the starch cleaning in the cleaning pool, but the cleaning time is long, starch loss. Modern corn starch factory starch cleaning using spin liquid separator for cleaning, generally 9 to 14 levels of spin liquid separator processing. According to the determination, from the centrifuge out of the starch milk protein content of not more than 2.5%, after 9 levels of spin liquid separator treatment, the protein content of the finished starch can be reduced to 0.35%.
8. Centrifugal separation and drying
The starch milk coming out from the spin-liquid separator contains 78% moisture, and if the starch workshop is combined with the starch sugar workshop, it can be sent directly to the starch sugar workshop for use. There is no need to dehydrate and dry the starch emulsion. But the starch emulsion obtained from the washing drum contains water and must be dehydrated.
The starch milk into the centrifugal separator for dehydration, can get the moisture content of 45% of the wet starch, this wet starch can also be used as a finished product factory. In order to facilitate transportation and storage, it is preferable to carry out drying treatment to reduce the moisture content of the starch to 12% of the equilibrium moisture. Then as a finished dry starch factory.
In order to ensure that the fineness of the finished product is uniform, sometimes also need to be finished product finishing. It is first processed by sieving to sieve out the starch of specified fineness, and the sieve tops are sent to the pulverizer to be crushed, and then sieved again to make all the products reach the specified fineness.
9. By-products processing
In the production of corn starch process, you can get corn syrup, germ, slag and protein water and other intermediate products, if processed, can be utilized as by-products. Corn main by-products processing methods are as follows:
(1) corn syrup: countercurrent immersion of corn with sulfur dioxide solution, and finally pumped out of the immersion water containing dry matter 6 to 7%, you can use a triple-effect vacuum evaporation, it will be concentrated to contain 50% of the dry matter of the thick liquid, known as corn syrup. According to the chemical composition of corn syrup measured as follows:
Moisture 48 ~ 50% Reduced sugar 5.5% or more Ammonia content of 3.6% or more
Inorganic matter 10% or more Ammoniacal nitrogen 0.9% or more Lactic acid 9 ~ 12% or more
Corn syrup in addition to be used as a raw material for the cultivation of yeast and antimicrobial nutrients and the manufacture of phytomene and myo-inositol, and the recycling of maize proteins and coarse and fine residue mix, is also very good animal feed.
(2) corn germ: from the sieving section of the cleaned germ contains about 50 to 60% moisture, can be used drum dryer or boiling machine to dry it to the moisture content of 4%. Usually three levels of drying, the first level of drying to the germ moisture content of about 35%; the second level of 10%; the third level to reach the specified moisture content of the germ.
The dried germ contains 45 to 50 percent oil. It has a higher oil content than soybeans (soybeans contain about 20% oil), so it is a good oilseed. Crude corn oil squeezed by the oil press is yellow, containing free fatty acids, and then by refining, to get refined corn oil can be eaten, the oil cake can be used as feed.
(3) protein water: from the flow tank, disk separator or spin liquid separator to get the protein water, also known as gluten water or yellow pulp water. The concentration of protein water is low, but the protein content in the dry matter is high. The filtration is poor, so it is not possible to recover the suspended proteinaceous material in it directly by filtration. It is usually separated by intermittent sedimentation in a settling tank or by concentration centrifuge. Concentrated protein mixed with fine residue, filtration, drying, crushing and sieving, to get the protein powder containing 10 to 12% moisture, also known as gluten, containing protein in more than 40%, can be used to formulate the raw materials of feed.
(4)Drying of slag and corn syrup: the coarse and fine slag obtained from the sieve top of the sieving equipment contains about 85% or more moisture, and it is first dewatered by the press, so that the moisture content is lowered to 55-70%, and then mixed with corn syrup. Since the acidity of corn slurry is high, lime is used to neutralize the acidity of corn slurry before mixing with the slag, and then it is mixed and dried to a moisture content of 12% or less. Its chemical composition is as follows:
Moisture 11-13% Crude fat 2% or less Crude protein 18% or less
Crude fiber 9% or less Ash 8% or less Soluble protein 50% or more
From the above data, it can be seen that the protein content is high and can be used as a good animal feed.
Use
At present, the starch industry is developing rapidly, and there are more than 100 kinds of processed products with corn starch as raw material, which are widely used in the industries of food, medicine, chemical industry, textile and paper making.
In the pharmaceutical industry, corn starch is an important raw material for the production of glucose, or the production of penicillin, streptomycin and other antimicrobial agents such as the main component of the culture medium, but also some of the tablets of drugs additives;
In the chemical industry, corn starch is used for the production of acetic acid, acetone, butanol and other chemical products; in the textile and paper industry, the main use of high straight-chain amylose maize starch as sizing agent and product surface coating.
In life we mainly use it to code flavor sizing, is processed into slices, strips, silk, d and other shapes of small pieces of raw materials, add salt, cooking wine, chicken essence, starch, ginger, green onion (some add green onion and ginger water) and egg together to grasp (some need to be stirred vigorously), so that each piece (strip) of raw materials uniformly wrapped in a thin layer of slurry, mainly used for slippery stir-fry, slippery buttery, bad buttery, vinegary buttery, blanch, Explosion and other techniques into dishes before cooking flavor method. This method is suitable for the tender texture, or choose the tender parts of the chicken, duck, goose "three birds" and pigs, cattle, sheep "three animals", as well as fish, shrimp, crab and other fresh seafood raw materials. The code flavor sizing has the effect of making the raw materials in addition to the foreign flavor, the dishes have the bottom flavor, to maintain the tender taste of fresh and crisp.
Nutritional Analysis
1. corn is recognized as the world's "golden crop", its fat, phosphorus, vitamin B2 content of cereal foods;
2. cornmeal contains linoleic acid and vitamin E, can make the body cholesterol levels, thereby reducing the occurrence of atherosclerosis;
2. cornmeal contains linoleic acid and vitamin E, can make the body cholesterol levels, thereby reducing the occurrence of arteriosclerosis. Occurrence;
3. cornmeal contains more calcium and iron, which can prevent hypertension and coronary heart disease;
4. modern medical research shows that cornmeal is rich in glutathione, which is a kind of anticancer factor, in the body can combine with a variety of foreign chemical carcinogens, so that it loses its toxicity, and then through the digestive tract out of the body. Coarsely ground cornmeal contains a large amount of lysine, which can inhibit tumor growth;
5. Cornmeal also contains the trace element selenium, selenium can accelerate the decomposition of oxides in the body and inhibit malignant tumors;
6. Cornmeal is rich in dietary fiber, which can promote intestinal peristalsis, shorten the time for food to pass through the digestive tract, and reduce the absorption of toxic substances and the stimulation of carcinogens on the colon, thus can Reduce the occurrence of colon cancer.