Maize Processing

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The steps in maize processing

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Madam, Is it possible to forward the presentation to me at shiv1823l@gmail.com. Farmers in Maharashtra, will be benefited. Regards

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Maize Processing:

Maize Processing

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Maize is cultivated in all but mainly six districts in Sri Lanka, (Anuradhapura, Ampara , Badulla , Moneragala , Matale and Batticaloa , where the area is over 2000 ha.) These districts, popularly called "the maize belt", account for over 80% of the land planted to maize in the country.

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Worldwide production of maize is 785 million tons, with the largest producer, the United States, producing 39%, while China produces 19% and Africa produces 6.5%.

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Endosperm 82% Germ 12% Bran 5% Tip Cap 1% Total: 100%

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Starch The major component is starch, (72% to 73% of the kernel weight. Other carbohydrates are simple sugars (glucose, sucrose and fructose - 1% to 3% of the kernel) The starch is made up amylose , (linear molecule)- 25-30%, and amylopectin (branched)- 70-75%. Waxy maize contains a starch that is 100 percent amylopectin .

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Protein The endosperm of maize contains a group of four structurally distinct alcohol-soluble proteins called ‘ zeins ’ ( α , β , γ and δ ). Thay are more abundant in the endosperm than in the embryo. zeins usually account for 50 to 70% of the endosperm protein and are characterized by a high content of glutamine, leucine and proline . zeins are devoid of lysine and tryptophan.

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Corn gluten The term gluten in reference to the cohesive, elastic protein mass remaining after starch is washed from a dough. Strictly speaking, gluten is found only in wheat because it is difficult to wash a cohesive protein mass from any other cereal flour relative to wheat. However the use of the term “Gluten” by the corn industry has become common in recent years. It refers to corn storage proteins in which only contain prolamine but not gliadin as in wheat.

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Oil and fatty acids Mainly from the germ (3% to 18%). Maize oil has a low level of saturated fatty acids ( palmitic and stearic acid). On the other hand, it contains relatively high levels of polyunsaturated fatty acids, mainly linoleic acid.(and small amounts of linolenic and arachidonic acids) Relatively stable since it contains only small amounts of linolenic acid and high levels of natural antioxidants. In this respect, populations that consume degermed maize benefit less in terms of oil and fatty acids than populations that consume whole-kernel products.

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Dietary fibre After carbohydrates, proteins and fats, dietary fibre is the chemical component found in the greatest amounts (comes from the pericarp > the endosperm cell walls > the germ cell walls). Mainly insoluble fibre . Thay are cosists of hemicellulose , cellulose and lignin Dietary fibre content in dehulled kernels would obviously be lower than that of whole kernels.

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Minerals The concentration of ash in the maize kernel is about 1.3%, only slightly lower than the crude fibre content. Environmental factors probably influence the mineral content. The germ is relatively rich in minerals, with an average value of 11% as compared with less than 1% in the endosperm. The most abundant mineral is phosphorus, found as phytate (salts of the phytic acid - C 6 H 18 O 24 P 6 )of potassium and magnesium. As with most cereal grains, maize is low in calcium content and also low in trace minerals.

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Fat-soluble vitamins The maize kernel contains two fat-soluble vitamins: provitamin A or carotenoids , and vitamin E. Carotenoids are found mainly in yellow maize, while white maize has little or no carotenoid content. Most of the carotenoids are found in the endosperm and only small amounts in the germ. But unfortunately yellow maize is not consumed by humans as much as white maize. The other fat-soluble vitamin, vitamin E is found mainly in the germ. The source of vitamin E is four tocopherols ( α , β , γ and δ ), of which alpha- tocopherol is the most biologically active. Gamma- tocopherol is probably more active as an antioxidant than alpha- tocopherol .

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Water-soluble vitamins Found mainly in the aleurone layer, followed by the germ and endosperm. This distribution is important in processing as significant losses of the vitamins. (thiamine , riboflavin) The low availability of nicotinic acid is important because of its association with niacin deficiency or pellagra, which is prevalent in populations consuming high amounts of maize. Some processing techniques hydrolyze niacin, thereby making it available. The association of maize intake and pellagra is a result of the low levels of niacin in the grain. Maize has no vitamin B12, and the mature kernel contains only small amounts of ascorbic acid. Other vitamins such as choline , folic acid and pantothenic acid are found in very low concentrations.

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Many forms of maize are used for food, sometimes classified as various subspecies related to the amount of starch each had: Flour corn — Zea mays var. amylacea Popcorn — Zea mays var. everta Dent corn  — Zea mays var. indentata Flint corn — Zea mays var. indurata Sweet corn — Zea mays var. saccharata and Zea mays var. rugosa Waxy corn — Zea mays var. ceratina Amylomaize — Zea mays Pod corn — Zea mays var. tunicata Larrañaga ex A. St. Hil . Striped maize — Zea mays var. japonica

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THE MANY USES OF CORN Corn has many uses in today’s society. It is used for industrial purposes, food, drug, and cosmetic uses, and as an animal feed. Here are a few examples. ► Food – Eat little whole kernel corn, but we eat more in processed foods. ► Starch – use as a raw material or an additive for many process foods. ► Alcohol – e.g. Ethanol; use as fuel for cars and a variety of other engines and as raw material for liquor production. ► Sweeteners – Corn syrup is used as a sweetener in products like soda and candy. ►Animal Feed – Feed for cattle and poultry continues to be the largest market for corn.

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Harvesting Care should be given to limit the amount of kernel damage. Moisture content should be Maitained at the optimum level for limiting mechanical damage during harvest (about 22%.) Increased damage occurs both below and above this moisture content.

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Shelling The separation of corn kernels from the cob is called shelling. This can be done with different types of machines, e.g. - spring type - power-driven cylinder-type

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Maize and Aflatoxin What are Aflatoxins ? They are naturally produced by the Aspergillus flavus and related fungi. A. flavus fungus present in the soil and air, can infect maize at any stage from preharvest to postharvest storage Preharvest contamination: - Growth cracks, mechanical injury and damage by pests to the plant parts or seeds leads to infestation by fungi - Toxins are produced under high temperatures, drought, and terminal water stress prior to harvest. Postharvest contamination: - Fungi continue to grow and produce aflatoxins under high moisture and warm temperatures. - This process is enhanced if drying is delayed. Damage by insect or rats can also facilitate mold invasion and toxin production during storage.

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Why Aflatoxins should be avoided? They cause illness to humans and animals -cause liver cancer, affects body's immune system and cause growth retardation) - also associated with malnutrition syndrome, and can lead to even death They cause economic losses - Result in ill health and lowered animal production - lower grain’s market value and export potential - Make an extra cost of management and monitoring.

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Reducing the Risk of Aflatoxin Contamination in Maize Preharvest Plant maize at correct whether and harvest at correct maturity. Remove dead plants and plants showing pest or pathogen attack and weeds Protect crop from corn borer damage. Visually inspect cobs for fungal infections/damage on the grain and discard the affected cobs. Reducing the Risk of Aflatoxin Contamination in Maize Postharvest Avoid mechanical damage to seed during harvesting, drying and storage. Rapidly dry the grain down to 14% moisture content and store the seeds. Clean grain bins/storage areas before putting the new crop. Stock cobs or seeds in bags on wooden plank and store them in well aerated waterproof area. Avoid stacking of harvested crop with damaged cobs intact.

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Chemical treatment sodium bisulphite Ammonia propionic acid – More effective and retain the grain quality Proper drying to control aflatoxin maize is first field dried on the stalk for one to two weeks before harvesting to reduce moisture content to 18 to 22%. It is next shelled within 24 to 48 hours of harvest, and loaded into a drier within 12 hours of shelling thereby reduce the moisture content to 14%, with no part exceeding 15%. Aflatoxin content is monitored rapidly by a special adaptation of the bright greenish-yellow fluorescence (BGYF) test. Dryied maize can be safely stored for a minimum of two months with no increase in aflatoxin content. Add odours and darker the colour

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Maize is milled either by a dry or wet milling process What is the difference between wet and dry milling of maize? Wet milling is used to obtain oil, gluten, starch and starch hydrolytes. Contrary to the dry-milling process, the wet-milling process uses large amounts of water to steep kernels and thereby separates out the germ, and then separates the germ into oil and meal; (100 grams of maize produces about 3 grams of oil. Corn oil is commonly used in foods because of its neutral flavour , ability to withstand heat and presence of high level of polyunsaturated fatty acids. The kernel’s meal portion becomes starch, gluten and bran.)

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Dry milling is done to convert maize into animal feed, beer, breakfast cereal and other food ingredients, such as corn-meal.

Wet Milling Process of Maize:

Wet Milling Process of Maize

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Corn Cleaning The incoming corn for milling contains dust, cracked corn pieces of cob and stock and metallic objects like nut and bolt that can cause severe problems in the Wet Mill. Corn cleaning is accomplished by using a series of woven wire screens and compressed air blow. Larger objects like cobs, bolts and scrap metal are retained on the trash screen (largest openings) and corn and cracked corn passes through the screen. The cleaned corn is retained on the cracked corn screen(small openings), while the cracked corn passes through the screen. Cleaned corn transfers to the steeps, while cracked corn either fully or in part, mixed with fiber or is sold separately. The air blow removes the lighter impurities.

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Disc separator is used to remove the other types of grains Magnetic chambers are used to remove any remaining metallic particles

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Steeping The main purpose of steeping is to separate the water-soluble substances from the corn and to soften the kernels, so that these become amenable to the subsequent mechanical separations. Furthermore steeping prepare the corn kernel physically and chemically for subsequant milling by hydrating the corn kernel, toughening the fibre , breaking some chemical bonds within the protein matrix and swelling and softening the germ. Thereby, the cleaned grain is placed into several steep tanks. In steeping keep the kernels in contact with warm process water for a certain period of time. The water is routed in the reverse order of the filling sequence such that the tank that has held corn the longest gets the freshest steep water. (therefore, water requirement is minimised ).

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The steep tanks are heated by connection to a heat exchanger. The maximum temperature in the steep tanks is controlled permanently, temperatures above 54 °C are voided, as bacterial growth is significantly retarded above this temperature, temperatures below 48 °C are also avoided, because wild yeasts can begin to grow. Sulphur dioxide is added to the process water to accelerate the process and to prevent the sprouting of the corn and growth of bacteria. Sulphur dioxide brings the initial steep water to a pH of about 2.2 (inhibition of lactic acid bacteria growth, as well as softening the corn protein, breaking of disulphide bonds withing the zein protein matrix, which encases the starch granules). Freeing the starch granules allows a cleaner separation of the protein and starch later in the process. After this process, the steep water is termed light steep water, which can be processed/evaporated for sale or used as a nutrient source on-site for the ethanol fermentation.

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Steep Evaporators Light step liquor is concentrated in a Steep Water evaporator. The concentrated steep liquor is pumped to storage and/or selected quantities can be mixed with the dewatered fiber prior to drying.

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Grinding mills and Germ separation After steeping, the softened corn grinded in first and second grind mills to break the kernel and release germ out of corn. In corn milling process special design teeth-disk type de-germination mills are used. These mills breaks softened corn into parts while germ remains as whole.

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Steeped corn is fed to the first grind mill, which crushes the kernels, enabling separation of the germ. A substantial part of the starch is then released. The grinding is done in two steps, viz. in the first grind mill and in the second grind mill. Each grinding step is flowed by separation of the germ fraction in a two-stage Germ Hydro Cyclone degerminating system and respectively. The underflow from the first Germ Hydro Cyclone system gravitates to a Screen Sieve. The overflow from this Screen Sieve gravitates to the second grind mill. The germ is removed in the overflow of the first stage of the first Hydro Cyclone system. This flow also contains a certain amount of starch. To recover this starch the germ fraction is washed out in a screen Sieve system, using process water. The washed germ are dewatered in an expeller press and conveyed to the germ dryer.

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The underflow from the second Hydro Cyclone system is pumped to a Screen Sieve Bend where the first starch is extracted (screened mill starch). The overflow of this screen gravitates to the third grind or refiner mill. The ground material from the third grind mill is pumped to a multi-stage Screen Sieve system. The underflow from its first stage is the remainder of the screened mill starch. The overflow, containing the fiber fraction, is pumped to the subsequent stages and washed, with process water, to recover entrained starch. The fiber fraction leaves the last stage of the Screen Sieve system with an amount of water, necessitating a dewatering step prior to drying of the fiber. Dewatering is done in two stages, viz. a Screen Sieve followed by an expeller press. The dewatered fiber is conveyed to the feed dryer. The screened mill starch contains starch, gluten and water and, possibly, small quantity of fine fiber and heavy impurities. Removal of heavy impurities is effected in a two-stage Hydro Cyclone degritting system.

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BACK

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Germ wash and Germ dewatering Typically, germ is washed in few step to separate the starch remaining in the fluid from germ cyclones and to prepare the germ for germ dewatering press. Germ press drops the moisture of germ for less energy consumption in germ drier.

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Fiber separation Fiber separation consists of four steps: initial screening of coarse fibre milling or grinding step to liberate and disperse all the starch and gluten from the remaining fibre washing step on a screen dewatering and drying step with the addition of corn steep liquor

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Starch and Gluten Separation The screened mill starch (starch milk) contains all the dissolved proteins (gluten). The gluten separation process is centrifugation (using centrifugal separator or primary separator), based on density differences between starch and protein. The starch is diluted and washed in hydro-cyclones until all protein residues are removed. The underflow is concentrated starch milk. The overflow from the primary separator contains the gluten fraction.

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Dehydration and drying The refined starch is dehydrated by centrifugation and dried on a flash dryer. The wet mill process is just the beginning stage for the production of many different products; e.g. starch, gluten meals fuel, ethanol. sweeteners corn oil

Dry Milling Process of Maize:

Dry Milling Process of Maize

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Corn is dry milled by either a tempering/ degerming or a ground stone/ nondegerming system. The main products of tempering / degerming process are -Flaking grits (large grits) -Brewers grits (Small grits) -Corn meal (coarse powder) -Corn flour (fine powder) -Animal feed including germ

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Flaking Grits : The large size grits obtained, as the top fraction is a premium product in the developed countries where corn flakes are popular as breakfast cereal. Brewers Grits : Maize grits are used as adjuncts to barley malt in beer manufacture. Normally for 3 parts of barley malt, one part of grits is used. This ratio varies based on type of beer. Maize Meal ( Suji / Rava ) : Coarse powdery fraction finer than grits is termed maize meal. The main end uses are in making snack foods, and bakery items. Considering the huge Indian market for these items selling maize rava should be easy. Corn Flour : The fine powder obtained during milling is termed corn flour. It can be made use of in preparations where other flours are used. Rural folks make rotis with corn flour. It is used in biscuit and bakery production. It can be fortified with Soya meal resulting in a high protein, high-energy food. Bran/ germ : The pericarp of maize kernel on powdering is termed bran. This is rich in proteins and finds ready market from feed industry. The germ contains oil. In small mills a mix of bran and germ is sold as cattle feed.

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Tempering of corn Incoming corn is tempered for 10-45 minutes by adding water (liquid or steam) to raise the moisture content of the grain. The moisture will primarily enter through the tip cap (cob attachment point) of the kernel and be absorbed by the germ and the cells between the pericarp (outer seed covering) and the endosperm. This moisture differential between various kernel components promotes efficient separation of the endosperm from the pericarp and germ. The tempered corn enters a degerminating mill.

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Corn Cleaning Hammermills Mix Slurry Liquefaction alpha amylase enzyme CO2 Cooker Yeast and Glucoamylase enzyme Fermentation D I S T I L L A T I O N Whole stillage Ethyl Alcohol Centrifuge Evaporator coarse solids thin stillage Rotary Dryer Distillers Wet Grains Distillers Dried Grains with Solubles Cond. Distillers Solubles Corn

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Unloading Corn is unloaded into storage bins Milling/ Grinding Corn first passes through a hammer mill in which grind the kernels into flour which is referred to in the industry as “meal”. Mashing Water and enzymes are added to the meal to produce what is known as “mash”. Cooking The cooker heats the mash to 210 degrees, liquefying the starch. The heat help reduce levels of bacteria in the mash by 90%. Saccharification Enzymes are added to the mash to convert the starch to dextrose, a simple sugar. Cooling The mash continues on through heat exchangers that cool it to 90 degrees – anything hotter would kill the yeast added during. Fermentation Yeast is added to the mash to ferment the sugars. During this process the yeast eat the sugars and in the process produce heat, ethanol and CO2. It takes 48 hours for the mash to make it through the fermentation process. Distillation After fermentation the mash is called beer. Beer is made up of 15% alcohol and 85% non fermentable and is ready for distillation. During distillation the beer is continuously pumped through a multi column system that separates the alcohol and stillage . The alcohol moves on to dehydration. The stillage is processed into distillers grains. Dehydration The alcohol circulates through a molecular sieve to capture the last bit of water. At the end of this process, the ethanol is in high purity. A small bit of gasoline is added to make it unfit for human consumption and avoid taxes levied on alcohol. Ethanol Storage Finally the ethanol is pumped into storage tanks. It is then ready for shipment to gasoline terminals or retailers. Stillage The stillage is sent through a centrifuge that separates the coarse grain from the solubles . The solubles are then concentrated to about 30% solids by evaporation, resulting in Condensed Distillers Solubles (CDS) or “syrup”. The coarse grain and the syrup are then dried together to produce Dried Distillers Grain with Solubles (DDGS), a high quality, nutritious, livestock feed.

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C0rn Cleaning C0rn Steep Tanks Germ Separation Grinding Mills Washing Screens Centrifugal Separation Germ Extraction Starch washing Hydro clone Steep water Evaporation Starch and Nutritive Sweetners Corn Gluten Meal Corn Germ Meal Corn Gluten Feed Condensed Fermented Extracted Corn Oil

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Corn Quality control Separator Aspirator Disc separator Scourer Magnetic Separator Washer stoner Steeping Grinding Screening Germ separation Germ Oil refining Corn oil Starch – Gluten separation Wet gluten Gluten meal dry, 60% prot Fiber Gluten feed wet of dry Starch Drying Starches Fermentation Starch conversion Ethanol Chemicals Syrup refining High fructose corn syrup Corn syrup Dextrose

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