Maize wet-milling

List at least three by-products of the maize wet-milling industry, indicating chemical composition and main industrial or feed uses. 

Imported maize is the raw material for several food ingredients used in the bakery industry. While maize can be dry milled like wheat, it is more commonly wet milled. The wet milling process is much better suited to separating the different components of maize so that the oil, the protein and the starch can be recovered separately. Maize starch is used directly in bakery products as corn flour, so-called even in the UK. 

Wheat is normally dry milled. Maize can be dry milled but is normally wet milled. The wet milling process allows the maize to be fractionated into starch protein and oil. 

The methods used to separate the starch vary, depending on the raw material. Maize is normally wet milled. Initially the maize kernels are steeped in dilute sulfuric acid for 40 50 hours to soften the kernels. Next, the kernels are milled to release the germ that contains the oil. The fibre is then separated from the endosperm by milling it finer. Centrifuges are then used to separate the starch from the protein. After this the starch is washed and dried. 

Le Bras, A. 1982. Maize drying conditions and its resulting quality for wet-milling industry. In Maize Recent Progress in Chemistry and Technology , pp. 95-127. Academic Press, Orlando, FL. 

Moheno-Perez, J.A., Almeida-Domingues, H.D., and Sema-Saldivar, S.O. 1999. Effect of fiber degrading enzymes on wet milling and starch properties of different type of sorghums and maize. Starch/Stdrke 51, 16-20. 

Zehr, B.E., Eckhoff, S.R., Nyqyist, W.E., and Keeling, P.L. 1996. Heritability of product fractions from wet milling and related properties of maize grain. Crop Sci. 36, 1159-1165. 

Among oxidizers used have been sodium hypochlorite, potassium permanganate, and hydrogen peroxide. Bisulfite is commonly used in the wet milling of corn (maize) and in processing wines, fruit juices, jams, and dried fruits. 

Hojilla-Evangelista, M.P., Johnson, L.A. and Myers, D.J. (1992) Sequential extraction processing flaked whole maize - Alternative technology for wet milling. Cereal Chem., 69, 643-647. 

A major vegetable oil, with a production of around 2 million tonnes per annum from maize (Zea mays), is obtained by wet milling, particularly in the United States. The major acids are palmitic (9%-17%), oleic (20%-42%), and linoleic (39%-63%), and the major triacylglycerols. Refined corn oil is 99% triglyceride, with proportions of approximately 59% polyunsaturated fatty acid, 24% monounsaturated fatty acid, and 13% saturated fatty acid. ... 

Dried by-product from the manufacture of maize starch by wet milling. It is composed of bran and gluten, to which the steeping liquor and germs, deoiled or not, may be added (n = 2609). 

CAS 8001-30-7 EINECS/ELINCS 232-281-2 Synonyms Corn oil Maize oil Zea mays Zea mays oil Definition Refined fixed oil obtained from wet milling of corn, Zea mays Properties Pale yel. oily liq., faint char, odor and taste sol. in ether, chloroform, amyl acetate, benzene, CS2, chlorinated and aromatic soivs. si. sol. in alcohol insol. in water dens. 0.914-0.921 m.p. -10 C acid no. 2-6 iodine no. 109-133 sapon. no. 187-193 flash pt. 321 C ref. index 1.470-1.474... 

The corn wet milling process is designed to efficiendy separate the maize kernel into three principal parts (ref Figure 4A.10) ... 

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