Abrefah et al./ Elixir Agriculture 39 (2011) 5000-5003 5000 Introduction Maize is an important staple food grown in many parts of the tropics which serves as food for many people and animals. In Ghana, it is the most popular of all grain crops and it is grown all over the country. Maize is processed into corn flour which is used in the preparation of many local foods such as kenkey, banku, tuo zaafi, akple, porridge, abolo etc. (Lokko et al, 2004). The corn mill is the machine used to process cereals, legume, nuts, and spices into flour. It is an indispensible tool in the flour production industry. It can be found in cities, towns and villages across the country due to the dependence on cereal food products by the country folks. It has a pair of circular grinding plates which are made of cast iron. Cast iron is normally used for machinery parts to resist wear and tear. Iron is alloyed with nickel, chromium, copper, molybdenum and silicon to increase the tensile strength (Johnson, 1977). Both surfaces of the plates have small ridges running from edge to center. Grinding is done by power rotating one mobile plate against a stationary plate. In the process, grains that pass between the plates are crushed to powder. The sliding process of the plates generates friction which leads to wear and tear. A casual observation of maize processing indicates that worn out metals are been processed into corn flour. Heavy metals often have direct physiological toxic effects. Some are stored in living tissues, sometimes permanently. According to Kwofie (2006), three different samples of locally manufactured grinding plates were selected from the same manufacturer and tested for chemical composition as well as hardness and wear. Although results showed that chemical composition were similar, the hardness and wear resistance of the samples were significantly different suggesting that samples were of different heats. Since the grinding plates were from the same production shop and meant for the same purpose, these differences in hardness and wear resistance indicated non- reproducibility of products. There are two locally manufacturing industries in Ghana, Tema and Kumasi. Other foreign grinding plates used by the corn mill operators are radget, amuda, rex, premier, bin and bamford. The higher the quality of the grinding plates the longer it takes to wear out and the safer it is because there would be less worn out metals in the corn flour. The plate type, the location of the mill as well as the method of grinding (whether milled with a corn mill or milled with pestle and mortar which are all made from timber) can affect the results. Timber is a natural solid wood from a tree which has been sawn into sizes suitable for building and construction purposes (Sackey et al, 2004). The objective of this work was to determine the concentration of heavy metals in corn flour ground by corn mills. It was also aimed at discovering which of the grinding plate materials produces the best levels of heavy metals. Figure 1 and 2 show examples of the wooden mortar and pestle and the corn mill respectively. Elixir Agriculture 39 (2011) 5000-5003 The effects of milling on corn flour using instrumental neutron activation analyses: a case study of three selected corn millers within Accra metropolis, Ghana R.G. Abrefah 1,2 , E. Mensimah 1 , R.B.M Sogbadji 1,2 and N.S. Opata 1 1 Ghana Atomic Energy Commission, National Nuclear Research Institute, P.O. Box LG 80, Legon-Accra, Ghana. 2 University of Ghana, School of Nuclear and Allied Science, P.O. Box AE1, Atomic, Accra, Ghana. ABSTRACT Most Ghanaian foods are made from maize. Unfortunately, certain diets made from the cereal cannot be produced without processing the maize into flour. The corn mill has been the most efficient and often used tool for grinding legumes, cereals, nuts and spices. Maize is milled either dried or soaked. Dry maize is usually milled over and over again for about four times to retain a smooth texture. It is used to prepare many delicacies in different parts of Ghana. However, soaked maize is milled only once and it is ready for use. The work was conducted to find the levels of Cd, Al, Ni, Cu, Mg and Zn in the processed flour using instrumental neutron activation analyses at the Ghana Research reactor-1 Facility. As the grinding plates of the corn mills rub against each other, there is friction as well as wear and tear. This could introduce toxic metals into the corn flour. Results showed that the corn mills had no negative effects on the corn flour as the level of the elements recorded were below the required limits. Al values in the sample ranged from 1.8 ± 0.27 mg/kg to 5.40 ± 0.81 mg/kg. Cu, Cd, Zn and Mn also recorded concentration values of ranges 0.70 ± 0.11 mg/kg to 1.50 ± 0.23 mg/kg, 4.80 ± 0.72 mg/kg to 6.40 ± 0.96 mg/kg, 0.52 ± 0.08 g/kg and 0.90 ± 1.35 mg/kg to 4.10 ± 0.62 mg/kg respectively. No particular process recorded consistent peak value concentrations for the heavy metals. Ni recorded concentrations within the range 26.18 ± 3.23 mg/kg to 46.42±2.53 mg/kg. However, continuous consumption could lead to accumulation of these elements that could affect the body adversely. © 2011 Elixir All rights reserved. Agriculture ARTICLE INFO Article history: Received: 7 August 2011; Received in revised form: 22 September 2011; Accepted: 30 September 2011; Keywords Instrumental neutron activation Analyses, Corn flour, Corn mill, Mortar, Pestle, Grinding plates. 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