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Corn Processing: Emerging Trends and Opportunities
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Friday, 18 September, 2015, 08 : 00 AM [IST]
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Dr Anurag Singh
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fiogf49gjkf0d Corn is one of the most important cereal crops of the world and contributes to food security in most of the developing countries. Corn is not only used for human food and animal feed but is also widely used for corn starch industry, corn oil production, ethanol production and so on. Corn can be cultivated in tropical, subtropical, and temperate climates due to its genetic variance.
Global scenario of corn production
Corn is a cereal crop which is cultivated widely throughout the world and has the highest production among all the cereals. Global corn production has grown at a CAGR of 3.4 per cent over the last 10 years from 716 MnMT in 2004-05 to 967 MnMT in 2013-14. The area under corn cultivation in the period has increased at a CAGR of 2.2 per cent, from 146 Mn hectare in 2004-05 to 177 Mn hectare in 2013-14.
Productivity of corn has increased at a CAGR of 1.2 per cent, from 4.9 MT/hectare in 2004-05 to 5.5 MT/ hectare in 2013-14. USA is the largest producer of corn in the world, followed by China and Brazil. USA is also the largest exporter of corn. Brazil, Ukraine and Argentina are the other main corn producing countries after USA. The major share of total corn export (80-85%) is held by these four countries. USA, Brazil, Argentina and India are the major exporters of corn while Japan, South Korea, and Mexico are the major importers.
Indian scenario - Corn production
Corn is grown throughout the year in India. It is a kharif crop holding 85 per cent of the area under cultivation in the season. Corn is the third-most important cereal crop in India after rice and wheat. It is having about nine per cent share of total food grain production in India. Production of corn in India has increased at a CAGR of 5.5 per cent from 14 MnMT in 2004-05 to 23 MnMT in 2013-14.
The area under corn cultivation in the period has increased at a CAGR of 2.5 per cent from 7.5 Mn hectare in 2004-05 to 9.4 Mn hectare in 2013-14. Andhra Pradesh and Karnataka are the major producers of corn contributing to ~38 per cent of the total production. Nine states viz. Karnataka, Andhra Pradesh, Tamil Nadu, Rajasthan, Maharashtra, Bihar, Uttar Pradesh, Madhya Pradesh and Gujarat account for 85 per cent of India’s corn production and 80 per cent of area under cultivation. Productivity of corn (yield) has increased at a CAGR of 2.9 per cent from 1.9 MT/hectare in 2004-05 to 2.5 MT/hectare in 2013-14.
Consumption pattern of corn
Corn is used as a staple diet in many developing countries but the major use of corn is for poultry feed (~50 per cent of total consumption). Corn consumption has increased at a CAGR of 3.6 per cent over the last five years globally. Corn consumption in India has increased at a CAGR of ~4 per cent over the last 10 years from 14 MnMT in 2004-05 to 19MnMT in 2013-14. In developed countries like USA and members of European Union, a very low ratio of corn is used for direct corn consumption as most of the corn is used for production of feed, starch and ethanol.
Utilisation of corn for human consumption
A variety of products for human consumption are prepared from the corn meal obtained by milling. "Baby corn” is used as vegetable in many countries. It is also consumed fresh or canned. Some examples of products prepared from corn are as follows:
- In Africa, the grain is usually parched and eaten. The corn grain is popped in hot sand (Africa and Asia) or mostly in a hot plate and eaten hot as popped corn. "Corn nuts," roasted floury grains, are very popular in Andean regions and even in USA.
- The grain is boiled and eaten whole or the grain is beaten and pulped to make a product similar to boiled rice. This is consumed in African and Asian countries.
- A type of soup or a traditional dish known as "pozole" is prepared by cooking the grain in lye or lime water and removing the pericarp. It is popular in Mexico.
- Ogi or Uji is consumed in Africa that is a porridge prepared by steeping, fermenting making slurry of grain.
- Cooked paste is prepared in Africa from dry milled meal.
- The flour is used for making chapattis in Asia.
- In Ethiopia, the dough is fermented and cooked in a hot plate to prepare the Enjera of corn.
- The grain also can be used to make corn meal, biscuits, leavened bread and "corn bread."
- The grain is soaked and cooked in a water or lime solution then the grain is ground to make dough which is used as the base for different preparations. This product can be pounded to obtain the grit and then cooked and eaten as the rice boiled or can be used to prepare special type of breads such as the arepas in Venezuela or the sopas in Paraguay.
- Fermented drinks of corn gruel are popular in Africa and Latin America (chicha and pozol).
- The corn flour is being used to supplement wheat flour for making bread and biscuits.
Industrial utilisation of corn
Basically, there are two milling processes (wet milling and dry milling) used for making various food, feed or industrial products from corn. The dry milling of corn produces distillers grains plus solubles, and the wet milling process produces starch and corn gluten feed. These feeds can be marketed as wet feed, or they can be dried and marketed as either dry corn gluten feed or dry distillers grains with or without solubles. There are many products from corn that have been taken over by industry and manufactured and marketed at commercial scale. These products include tortillas, corn flours (masa), chips and several types of snacks, breakfast cereal, thickness, pastes, syrups, sweeteners, grits, corn oil, soft drinks, beer, and whisky.
In general, at large-scale, the wet milling process is more used than dry milling process. The wet milling process apparently allows efficient removal of aflatoxins and impurities from corn along with other advantages. Wet milling process gives various intermediate products which are used as primary raw material for other processes such as starch for syrup, germ for separating the oil and so on.
Production of starch, sugars and oil from corn
The wet milling process normally produces pure starch, sweeteners (dextrose, fructose, glucose and syrups including high fructose syrups), proteins, fibres, ethanol and corn oil from the germ. Corn gluten is used mainly as animal feed. Corn gluten can also be used as binding agent, additive for printing dyes, and pharmaceuticals. Starch of corn is the most important product of the wet milling process, and it is widely used for food and industrial applications. The starch and oil extraction account for about 70 per cent of the product, and the remaining 30 per cent is formed principally by proteins and fibres (consisting mainly of cellulose and hemicelluloses) which is converted in animal feed. The process of corn wet milled is to obtain starch, oil, cattle feed (gluten feed, gluten meal, germ cake) and the hydrolysis products of starch, liquid and solid glucose and syrups. The process includes the followings main operations:
Cleaning of corn
(Removal of dust, wastes, stone and insects)
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Drying (Temp. not more than 54 0C)
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Steeping (50 0C for 28-48 hrs in water added with 0.02 to 0.03% SO2)
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Germ Separation ? Cooking in Steam
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Milling or Grinding Oil Extraction ? Germ Cake
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? Corn Oil
Gravity separation of starch from protein using hydroclones ? Corn Gluten
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Starch ? Fermentation
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Hydrolysis of Starch ? Ethanol
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Syrups and Sugars
Production of various products of corn
The corn starch, obtained as intermediate product, is used in paper manufacture, textile, adhesives and packed foods, and as the starting material for the manufacture of syrups and dextrose sugar by hydrolysis. The starch obtained from the wet milling of waxy corn, also called "amioca," consisting mainly of amylopectin, is non-jelly and has clear, fluid, adhesive properties. Heated and dried corn starch/water slurries yield pre-gelatinised starch, known as "instant starch" as it thickens upon addition of cold water. Approximately half of the starch produced is converted into syrups and sugars depending on the extent of the treatment and the degree of purity desired in the final product. The conversion of starch into sugars can be done by enzymatic or acid hydrolysis. The syrups are produced by partial hydrolysis and the sugar/ dextrose by total hydrolysis. The acid hydrolysis process requires boiling the starch paste with a certain quantity of diluted acid. Generally hydrochloric acid is used for hydrolysis and the process ends when the degree of hydrolysis is achieved. Neutralisation of the slurry is done using neutralisers like sodium carbonate. The impurities and solid particles are removed by filtration, then the syrup is blanched and concentrated until a desired specific gravity is achieved. The sugar dextrose is obtained by a complete or total hydrolysis of the starch, and then the liquor is neutralised, filtered, clarified and concentrated. Finally, the product is crystallised. Glucose and dextrose obtained from hydrolysis of corn starch are used in beer, cider, soft drinks, pharmaceuticals, confectionery, baking and jams.
The starch obtained from corn can also be used for ethanol production using yeast fermentation. A mash is prepared from the starch. The pH of the mash is adjusted at 6.0 so as to carry out the conversion of starch into simpler sugars. A thermo-stable enzyme a-amylase is added to mash which breaks down the starch polymer and produces soluble dextrin. These dextrins are fermented by yeast and ethanol is produced. The germ removed from corn kernels is steam cooked and oil is extracted either by hydraulic press or by using solvent extraction process.
Other value-added products from corn
The dry milling products of corn are used for making various value-added products, e.g. the grits obtained are flaked for the manufacture of breakfast cereal corn flakes; other cereal products or snack foods. Fine grits are used as a brewing adjunct, providing up to 40 per cent of the mash. Corn grits can also be used for the manufacture of wallpaper paste and glucose by chemical hydrolysis. Granulated corn and corn flour is also used in various bakery products, instant mixes, infant foods and so on.
Future prospects in corn processing
The consumption of corn is increasing globally. As per the growing demand for co-products of corn for various uses in food industry, corn processing has a bright future ahead. The trend is now shifting from using corn only as feed or food purpose to process it into various value- added secondary products. It’s high time to invest in corn processing.
(The author is assistant professor, department of food science and technology, National Institute of Food Technology Entrepreneurship and Management - NIFTEM)
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