1. OVERVIEW
Maize (Botanical name: Zea Mays L) is one of the oldest cultivated crops in the world. It is also one of the most important cereal crops globally and in India it is the third most important crop after rice and wheat.
Maize, also known as corn, is a versatile crop grown over a range of agro climatic zones. In fact the suitability of maize to diverse environments is unmatched by any other crop and even every part of the maize plant has economic value: the grain, leaves, stalk, tassel, and cob can all be used to produce a large variety of food and non-food products. As it has yield potential far higher than any other cereal, it is sometimes referred to as the miracle crop or the ‘Queen of Cereals’. Additionally maize can be grown in all seasons viz; Kharif (monsoon), post monsoon, Rabi (winter) and spring.
Maize has varied uses in India, varying from feed to industrial products. The crop is primarily, more than 50%, used for poultry feed, nearly one-fifth used for human consumption (Food) and the rest is used in breweries as well as for industrial products. But the most useful product of maize is ‘Starch’ which is derived by wet milling processing of maize and has varied uses and widespread applications.
Figure 1 Consumption Pattern of Maize in India
Source: Directorate of Maize Research
Although starch can be produced from a number of sources like Corn (maize), sorghum, grain wheat, rice, potato, tapioca, arrow root, grains of barley, rye, oat and millets, yet Corn, rice and tapioca are the major sources in India.
1.1 Product Definition
Starch is a high polymeric carbohydrate with the molecular formula (C6H10O5)n where n varies from a few hundred to over one granules, usually made up of both a linear polymer (amylose) and a branched polymer which dissolves in hot water. Starch is found as the reserve carbohydrate in various parts of plants and is enzymatically broken down to glucose to other carbohydrates according to the metabolic needs of the plants.
Starch is broadly divided into two types- natural and modified. Natural starches also known as unmodified starches or simply starches are further classified into cereal and root starches depending upon its sources.
Figure 2 Classification of Starch
Source: NPCS Research
Natural Starches
Starch occurs naturally in the plants and its percentage varies with the plant and also in different parts of the same plant. Corn (maize) sorghum grain wheat, rice, potato, tapioca, arrow root and sago are among the important sources of natural starches.
Modified Starches
Modified starch, also called starch derivatives, is prepared by physically, enzymatically, or chemically treating native starch, thereby changing the properties of the starch. Starches are modified to enhance their performance in different applications. Starches may be modified to increase their stability against excessive heat, acid, shear, time, cooling, or freezing; to change their texture; to decrease or increase their viscosity; to lengthen or shorten gelatinization time; or to increase their visco-stability.
1.2 Product Uses & Applications
Starch is used extensively in a plethora of forms serving numerous industries. Some of them are listed below:
· As an adhesive in textile industry
· As a thickener in food industry
· For increasing paper strength in paper industry
· As a filler in pharmaceutical industry
· For manufacture of glucose and dextrose
· For manufacture of modified starch
1.3 By-Products of Corn Starch
Corn starch is derived by wet milling process of maize. During the wet milling process, other than starch, the following products are produced:
· Concentrated Steep Liquor: It is a mixture of soluble proteins, amino acids, carbohydrates, organic acids (e.g., lactic acid), vitamins and minerals. It is used as a nutrient for microorganisms in the production of enzymes, antibiotics, and other fermentation products. It is sometimes combined with other ingredients in corn gluten feed and widely used in complete feeds for dairy and beef cattle, poultry, swine, and pet foods. It may also be sold separately as a liquid protein source for beef or dairy rations.
· Gluten: Corn Gluten is used as a supplement in animal feeds, dog food and fish food.
· Germ Oil & Cake: Germ oil is mainly used in cooking, where its high smoke point makes it valuable frying oil. It is also a key ingredient in some margarine. Germ cake is used as livestock feed ingredients.
Maize starch can be further processed and modified to manufacture the following:
· Liquid Glucose
· Dextrose Monohydrate
· Dextrose Anhydrous
· Sorbitol
· Dextrine (Yellow & White)