What is the processing technique for starch?

This post was last edited by tangbingzhen on 2009-5-18 22:22. It generally includes processes such as conveying, crushing, coarse screening, fine screening, concentration, dewatering, drying, and final product screening. Many materials can be found online; with careful searching, standard process diagrams should be available. Generally, it is the design firm that provides excellent process diagrams when a factory is built. Process is important, but high-quality equipment is even more important. If necessary, you may consult the person directly: T1668@163.com

Raw corn ↓ Purification → Corn debris ↓ Sulfurous acid → ▲ Soaking → Diluted corn slurry → Evaporation and concentration → Concentrated slurry → Export ↓ ↓ Coarse grinding → Fiber residue ↓ Germ separation → Three-stage washing → Dewatering → Drying → Air transport → Packaging and storage ↓ Fine grinding ↓ Fiber separation → Washing → Dewatering → Drying → Grinding and air transport → Packaging and storage ↓ Sand removal ↓ Protein separation → Gluten concentration → Dewatering → Gluten drying → Grinding and air transport → Packaging and storage ↓ ▲ Cyclone separation ↓ Starch dewatering ↓ ▲ Air drying ↓ Air transport ↓ Packaging

This post was last edited by ssq1982 on 2009-6-28 at 15:59. Corn Starch Table of Contents [Overview] [Production Methods] 1. Cleaning 2. Soaking 3. Rough crushing of corn 4. Separation of the germ 5. Grinding of corn 6. Screening of starch • 7. Separation of proteins and washing of starch • 8. Centrifugation and drying • 9. Processing of by-products [Uses] Corn starch [Overview] Also known as maize starch. Commonly known as six-grain flour. A white powder with a slight yellow tint. Corn is soaked in 0.3% sulfurous acid, and then processed through steps such as crushing, screening, sedimentation, drying, and grinding to be produced. Ordinary products contain small amounts of fat, protein, and the like. It has a high moisture absorption capacity, which can exceed 30%. For properties and uses, see starch. 【Production Method】 　　 1. Cleaning 　　Remove various dusts, organic and inorganic impurities from the corn. To ensure safe production and product quality, impurities present in corn must be removed. The methods for cleaning corn mainly include screening and air separation. Equipment used for cleaning includes vibrating screens, specific gravity stone removers, permanent magnet rollers, and wheat washers. 　　Vibratory screens are used to remove large, medium, and small impurities from corn. Equipped with sieve pores: the first layer of the sieve surface features circular holes with a diameter of 17–20 millimeters, the second layer has circular holes with a diameter of 12–15 millimeters to remove large and medium-sized impurities, while the third layer uses circular holes with a diameter of 2 millimeters to eliminate small impurities. 　　The specific gravity stone remover is used to remove companion stones from corn. Due to the large size of corn kernels, their flat shape, and high specific gravity, it is necessary to increase the air volume and wind speed during operation; the wind speed passing through the fish-scale holes should be around 14 meters per second. The height of the protrusions on the fish-scale pores should also be increased to 2 millimeters appropriately. During operation, attention should be paid to the movement of the material on the surface of the fish-scale sieve; the air flow rate must be adjusted, and regular checks should be carried out on the discharge of stones from the outlet. 　　The permanent magnet drum is used to remove magnetic metal impurities from corn; it should be placed in front of the crusher in the corn field to prevent such metal impurities from entering the crusher. 　　A wheat washer can remove dirt and dust from corn. After cleaning, the ash content of corn can be reduced by 0.02–0.6%. 2. Soaking 　The common method for soaking corn involves using several or dozens of metal tanks connected together by pipes; a water pump is used to circulate the soaking water between these tanks, enabling countercurrent soaking. 　　Test results showing the addition of soaking agents to the soaking water indicate that lime water, sodium hydroxide, and sodium bisulfite are all less effective than sulfur dioxide; moreover, the concentration of sulfur dioxide should not be too high. This is because the dispersing effect of the sulfur dioxide-containing soaking solution on the protein network increases as the sulfur dioxide content rises. When the sulfur dioxide concentration is 0.2%, the protein network dispersion is appropriate, allowing starch to be separated more easily ； At a concentration of 0.1%, sufficient dispersion does not occur, making it difficult to separate the starch. Generally, it should not exceed 0.4% at most, because too high a concentration of sulfur dioxide leads to excessive acidity, which does not offer much benefit for soaking corn; on the contrary, it inhibits lactic acid fermentation and reduces starch viscosity. 　　The soaking temperature has a significant impact on the soaking effect of sulfur dioxide; increasing the temperature of the soaking water can enhance this effect. However, too high a temperature will cause the starch to gelatinize, leading to adverse consequences. A temperature of 50–55°C is generally suitable, as it prevents the starch particles from gelatinizing. 　　The soaking time is also closely related to the soaking effect. During the soaking process, the soaking water does not penetrate into the internal tissues of the corn kernels from all parts of their surface; instead, it enters the kernels through the loose tissue at the base of the kernels, where it then penetrates inward via the porous tissue in the layer beneath the bran. Therefore, it is necessary to ensure an adequate soaking time. After being soaked at 50°C for 4 hours, the germ part of the corn absorbs water to its maximum level; after 8 hours, the embryo part also reaches its maximum water absorption level. At this point, the corn kernels soften, and after rough crushing, the germ and bran can be separated. However, the protein network has not yet been dispersed and destroyed, and the starch particles cannot be released. If soaked further, it can disperse the protein network. After about 24 hours of soaking, the protein network in the soft embryo is essentially dispersed, and after about 36 hours, the protein network in the hard embryo is also dispersed. This is because the dispersion process of protein networks involves expansion first, followed by transformation into small spherical protein particles, and finally the destruction of the network structure. Therefore, to completely disperse the protein network, an immersion time of over 48 hours is required. 　　The corn soaking conditions in factories across different locations are not exactly the same. The general operating conditions are as follows: the sulfur dioxide concentration in the soaking water is 0.15–0.2%, and the pH value is 3.5. During the soaking process, sulfur dioxide is absorbed by the corn, causing its concentration to gradually decrease; the concentration of sulfur dioxide in the resulting soaking water is approximately 0.01–0.02%, with a pH value of 3.9–4.1 ； The temperature of the soaking water is 50–55℃ ； The soaking time is 40 to 60 hours. The soaking conditions should be determined based on the quality of the corn. Generally, older corn that has been stored for a long time has low moisture content, and hard corn requires more intensive soaking conditions, namely higher concentrations of sulfur dioxide, higher temperatures, and longer soaking times. 　　After soaking, the moisture content of corn should be over 40%. 3. Coarsely crushed corn The purpose of coarse crushing is mainly to break the soaked corn into pieces of 10 pieces or more, in order to separate the germ. 　　Disc crushers are mostly used for crushing corn coarsely. Coarse crushing can be carried out in two stages. For the first time, the corn was broken into 4–6 pieces to separate the germ ； It is crushed again into more than 10 pieces for the second time, causing all the germ to fall off, in order to carry out a second germ separation. 4. Germ separation 　At present, germ separation in China is mainly carried out using germ separation tanks. The advantage is relatively stable operation, while the disadvantages are large floor space, high steel consumption, and low separation efficiency, which generally does not exceed 85%. 　　There are also corn starch factories at home and abroad that use hydrocyclones. This type of separator is made of nylon; 12 separators are placed together on a single frame, with a total length of no more than 1 meter. It occupies little space, has a high production capacity, and an excellent separation efficiency of over 95%. 5. Corn grinding A mixture of corn fragments after the germ has been separated along with some starch; in order to extract the starch, it is necessary to grind this mixture, thereby breaking down the corn cells and releasing the starch particles, while also separating the fibers from the bran. 　　The quality of the grinding process has a significant impact on starch extraction. If it is ground too coarsely, the starch cannot be fully released, as it is carried away by the coarse residues, which affects the yield of starch. It is too fine, resulting in poor fiber separation and affecting the quality of the starch. 　　To effectively grind corn, secondary grinding is usually employed. The first grinding was carried out using a hammer mill, and after sieving the starch slurry ； Grind it a second time using a sanding disc with starch. Some use a universal grinder for the first grinding step; after sieving the starch slurry, they use a stone mill for the second grinding step. 　　Production practices in various regions have shown that emery grinding is superior to stone grinding: it has higher hardness, the grinding surface does not wear out easily, there is no need for frequent maintenance of the grinding surface, and it also offers higher grinding efficiency. Emery grinding has gradually replaced stone grinding. 6. Starch screening After the corn pieces are ground, a corn paste is obtained, and screening can be used to separate the starch from the coarse and fine residues. Common screening equipment includes hexagonal screens, horizontal shaking screens, curved screens, and centrifugal screens. 　　The sieve pores for screening starch should be determined based on the type of screening equipment and the quality requirements for the starch. The sieve holes of the hexagonal screen used for cleaning coarse residue have a diameter of 0.6 millimeters, while those of the screen used for fine residue have a diameter of 0.12 millimeters. The flat-shaking screen uses 7×× grade double-nylon material for its sieve holes intended for coarse residue, and 12×× grade double-nylon material for those intended for fine residue. To clean both coarse and fine residue, a 120° curved screen with six stages is utilized; its length is 1.6 meters. The gap width of the sieve holes in the first stage of this curved screen is 0.05 millimeters, while the gap width in the remaining stages is 0.075 millimeters ； The sieve holes of the rotor sieve plate of the centrifugal sieve are 2×0.24 millimeters. Generally, four sequential operations are used. 　　The amount of water required for screening coarse and fine residues is as follows: for every 100 kilograms of dry material, 230–250 liters of water is needed for screening coarse residues, while 10–130 liters is sufficient for fine residues. The water temperature should be between 45–55°C, it should contain 0.05% sulfur dioxide, and the pH level should be around 4.3–4.5. 7. Protein separation and starch washing The concentration of the starch slurry after separating the coarse and fine residues is 6–8 Bé, with about 11–14% dry matter content. The chemical composition analysis of the starch here is shown in the table below:
Component Content (%) Component Content (%)
Starch 88–92 Water-soluble substances 2.5–4.5
Protein 6–10 Sulfur dioxide 0.035–0.045
Fat 0.5–10 Fine residues 0.05–0.1 g/l
Ash 0.2–0.4
As can be seen from the table, apart from starch, the dry substances in the starch slurry mainly consist of protein and water-soluble substances; therefore, it is necessary to separate the protein and clean the starch. 　　Proteins are generally separated using flow troughs, but due to their large space requirement and low separation efficiency, centrifuges are increasingly being used for this purpose. However, the starch slurry is required to have low levels of residue in order to prevent clogging of the nozzles inside the disc, which could cause mechanical vibrations. 　　The crude starch slurry after protein separation must be washed. Starch washing is mostly carried out in washing tanks, but it takes a long time and results in significant starch loss. In modern corn starch plants, starch washing is carried out using hydrocyclones, with 9 to 14 stages of hydrocyclones typically being employed for this purpose. According to the measurements, the protein content in the starch slurry coming out of the centrifuge is no more than 2.5%; after treatment with a 9-stage hydrocyclone, the protein content in the final starch can be reduced to 0.35%. 8. Centrifugal separation and drying The starch slurry coming out of the hydrocyclone contains 78% water; if the starch processing unit is integrated with the starch sugar production unit, it can be sent directly to that unit for use. There is no need for dehydration and drying of the starch slurry. However, the starch slurry obtained from the washing tank contains water, and dehydration treatment must be carried out. 　　By feeding the starch slurry into a centrifuge for dehydration, wet starch with a moisture content of 45% can be obtained; this wet starch can also be sold as a finished product. For easy transportation and storage, it is best to carry out drying to reduce the starch moisture content to the equilibrium moisture level of 12%. It is then exported as finished dry starch. 　　To ensure uniform fineness of the finished product, finishing treatment is sometimes also required. First, a screening process is carried out to separate out the starch of the specified fineness; the material that passes through the sieve is then sent to a crusher for grinding, followed by another screening step to ensure that the final product meets the required fineness standards. 9. By-product processing 　During the production of corn starch, intermediate products such as corn slurry, germ, residue, and protein hydrolysate are obtained; if processed, these can all be utilized as by-products. The processing methods for the main by-products of corn are as follows: (1) Corn syrup: Corn is soaked in a sulfur dioxide solution in a counter-current manner, and the soaking water, which contains 6–7% dry matter, is then pumped out. This liquid can be concentrated to a concentration of 50% dry matter using triple-effect vacuum evaporation; this concentrated liquid is known as corn syrup. According to the chemical analysis results of corn steep liquor, the following values are obtained: moisture content of 48–50%, reducing sugar content of over 5.5%, ammonia content of over 3.6%. The content of inorganic substances is over 10%, ammonia nitrogen content is over 0.9%, and lactic acid content is between 9–12%. In addition to being used as a nutrient source for cultivating yeast and antibiotics as well as a raw material for producing phytin and inositol, corn steep liquor can also serve as an excellent animal feed when mixed with recovered corn protein along with coarse and fine residues. 　　(2) Corn germ: The germ washed in the screening stage contains about 50–60% moisture, and it can be dried using a drum dryer or a boiling dryer to reduce its moisture content to 4%. Three-stage drying is typically used, with the first stage drying the germ to a moisture content of about 35% ； The second level is 10% ； The third stage achieves the specified moisture content for the embryo. 　　The dried germ contains 45–50% oil. It has a higher oil content than soybeans (the oil content of soybeans is about 20%), so it is an excellent oil crop. The crude corn oil obtained through pressing is yellow in color and contains free fatty acids; after refinement, it becomes refined corn oil that is suitable for consumption, while the oil cake can be used as feed. 　　(3) Protein water: Protein water obtained from troughs, disk separators, or hydrocyclones, also known as gluten water or yellow slurry water. The concentration of protein in the water is low, but the protein content in the dry matter is high. Its filtration efficiency is poor, so the suspended protein substances cannot be recovered directly using filtration methods. It is usually separated by intermittent sedimentation in a sedimentation tank or using a concentration centrifuge. The concentrated protein is mixed with fine residues, and after filtration, drying, crushing, and screening, a protein powder with a moisture content of 10–12% is obtained. Also known as gluten powder, this product contains over 40% protein and can be used as a raw material for formulating feed. 　　(4) Drying of slag and corn steep liquor: The coarse and fine slags obtained from the screening process contain more than 85% moisture; they are first dehydrated using a press to reduce the moisture content to 55–70%, after which they are mixed with corn steep liquor. Due to the high acidity of corn steep liquor, its acidity is first neutralized with lime before mixing it with the residue, after which it is mixed and dried to a moisture content of less than 12%. Its chemical composition is as follows: moisture 11–13%, crude fat less than 2%, crude protein less than 18%, crude fiber less than 9%, ash less than 8%, and soluble protein more than 50%. As can be seen from these figures, the protein content is high, making it an excellent feed for animals. 【Uses】 The starch industry is developing rapidly at present; there are over 100 processed products made from corn starch, which are widely used in industries such as food, pharmaceuticals, chemicals, textiles, and papermaking. 　　In the pharmaceutical industry, corn starch is an important raw material for producing glucose; it is also a key component in the media used to manufacture various antibiotics such as penicillin and streptomycin, and it serves as an additive in some tablet medications ； 　　In the chemical industry, corn starch is used to produce chemical products such as acetic acid, propylene, and butanol ； In the textile and paper industries, starch from corn with high amylose content is primarily used as a sizing agent and a coating for product surfaces. 　　In daily life, it is mainly used for coating ingredients with a seasoning mixture. Small pieces of ingredients that have been cut into slices, strips, threads, or cubes are combined with fine salt, cooking wine, chicken essence, starch, ginger slices, scallion segments (and in some cases, a mixture of ginger and scallion water), as well as egg liquid; these ingredients are then mixed thoroughly (in some cases, they need to be beaten until well combined) so that each piece is evenly coated with a thin layer of this mixture. This method is primarily used as a seasoning step before cooking dishes using techniques such as stir-frying, braising, cooking in vinegar, blanching, or stir-frying quickly. This method is suitable for poultry such as chickens, ducks, and geese with tender textures or those from tender parts, as well as livestock like pigs, cows, and sheep, and marine and river delicacies such as fish, shrimp, and crabs. Marinating with sauce helps to remove unwanted odors from the ingredients and enhance their flavor, giving the dish a distinct taste while also maintaining its tender and crisp texture. 　　【Nutritional Analysis】 1. Corn is recognized worldwide as a \"golden crop,\" ranking first among cereal foods in terms of its content of fat, phosphorus, and vitamin B2 ； 　　2. Corn flour contains linoleic acid and vitamin E, which can lower cholesterol levels in the body, thereby reducing the risk of arteriosclerosis ； 　　3. Corn flour is rich in calcium and iron, which can help prevent high blood pressure and coronary heart disease ； 　　4. Modern medical research shows that cornmeal is rich in glutathione, an anti-cancer agent that can bind to various foreign chemical carcinogens in the body, rendering them non-toxic, and then expelling them from the body through the digestive tract. Coarsely ground cornmeal contains large amounts of lysine, which can inhibit tumor growth ； 　　5. Corn flour also contains the trace element selenium, which can accelerate the breakdown of oxidants in the body and inhibit malignant tumors ； 　　6. The abundant dietary fiber in corn flour promotes intestinal peristalsis, shortens the time it takes for food to pass through the digestive tract, reduces the absorption of toxic substances and the irritation of carcinogens to the colon, thereby helping to decrease the risk of colon cancer. Modified starch: Modified starch is obtained by treating native starch in certain ways, thereby altering its original physical or chemical properties to varying degrees. 　　Modified starch is a type of starch that has been altered. This type of starch possesses some special physicochemical properties, and when added to food formulations, it enables the foods to have improved performance during processing or consumption. As long as it is edible, its physiological functions are no different from those of ordinary starch, and it can be consumed by children. 　　To improve the properties of starch and expand its range of applications, physical, chemical, or enzymatic treatments are used to introduce new functional groups onto starch molecules or to alter the size of these molecules as well as the properties of starch particles. This enables changes in the natural characteristics of starch, such as gelation temperature, thermal viscosity and stability, freeze-thaw stability, gelling capacity, film-forming ability, and transparency, thereby making it more suitable for specific application requirements. This type of starch, which has had its properties altered through secondary processing, is collectively referred to as modified starch. 　　The purpose of denaturation is, first, to meet the requirements of various industrial applications. For example, high-temperature processing techniques (such as canning for sterilization) require good viscosity stability of starch at high temperatures; frozen foods demand good freeze-thaw stability of starch; while jelly products need good transparency and film-forming properties. The second reason is to explore new uses for starch and expand its range of applications. For example: the use of starch in textiles ； Hydroxyethyl starch, hydroxypropyl starch as substitutes for plasma ； Highly cross-linked starch as a substitute for talc and similar materials used in surgical gloves

Wheat starch Wheat starch Starch is extracted from wheat. In the past, the fermentation method was used: wheat was soaked in water to soften it, then ground, and acid fermentation was carried out to dissolve the cells surrounding the starch particles, thereby making it easier to separate the starch. However, this method results in significant loss of gluten, and the proteins in the starch are difficult to remove completely, which affects the quality of the starch; it has now been replaced by the Martindale method. 　　 The Martindale method uses wheat flour as a raw material; water is added in an amount of 50–80% to it, and the flour is kneaded into dough at a speed of 40 revolutions per minute. Mix for about 30 minutes, then let it sit for 30 minutes to allow the gluten to swell and stick together, thereby facilitating the separation of the starch. Adding an appropriate amount of table salt can improve the quality of gluten and promote its cohesion. If the free acid content in the flour is high, an appropriate amount of calcium hydroxide can be added to adjust its pH value. After letting the dough rest for a while, add 5 to 8 times its volume of water and knead it, doing this in 3 to 4 stages. The emulsion obtained after washing is a starch milk, which requires refinement and purification; the residue is gluten, with a moisture content of 65–70%. After drying, its protein content is around 75–85%, and it can be consumed or used as a raw material for producing oil-based gluten. 　　The aforementioned method for extracting wheat starch involves staged processing and cannot be carried out continuously. Continuous production methods have been reported abroad; the processes are essentially the same, except that continuous equipment is required to be used for production. 　　 The Arsentin method: In recent years, there has also been the Arsentin method for producing starch from wheat as a raw material. The production principle of this method is the same as that of the corn starch production process. 　　Production method: Soft wheat with 14% moisture content and approximately 10% crude protein content is soaked in water containing 0.2% sulfur dioxide at a temperature of 39°C for 12 hours, allowing the moisture content to increase to 55%. The other operating methods are the same as those for corn processing. The crude protein content in the final starch product was below 0.4%, with a recovery rate of up to 83%