Knowledge and control of toxic chemical agents in cereals

Cereals are the fruits of cultivated grasses (Poaceae or Gramineae), the species of agricultural significance being primarily barley, maize, millets, oats, rice, rye, sorghum, triticale, and wheat. World-wide, cereals are a significant agricultural commodity for both man and his livestock. For the purposes of trade statistics, cereal production is usually broken down in terms of wheat, rice, maize, and other coarse grains (barley, oats, rye,etc.). It has been estimated that the world’s grain production in 2015e16 was in the order of 2.4 thousand million tons. Of additional relevance is the fact that although most cereals are frequently consumed in the country of origin, a substantial amount is exported and traded internationally. Given the significant degree of internal and international trade, provenance whether at a local or international level, is a significant factor in any risk assessment concerning the occurrence and possible hazards presented by chemical contaminants in cereals. Essentially, they consist of an embryo surrounded by an endosperm and aleurone layer, which in turn is surrounded by bran layers, which constitute the seed coat. Arguably the tissue of greatest nutritional significance is the endosperm. This is composed of cells filled with nutrients to sustain the embryo during the germination process. To obtain the greatest nutritional benefit from any grain, it must undergo some form of processing (discussed below) to increase both digestibility and palatability. Processing is typically physical in nature involving one or a combination of mechanical treatments. These can include threshing (removal of outer seed coats); milling (particle size reduction), leading to the conversion of grain into a flour of some type; and/or thermal processing (e.g., boiling or baking). It is the anatomy of the kernel that not only accounts for the dietary significance of cereals and the technology necessary to convert them into acceptable foods but also significantly contributes to the types and routes of chemical contamination, which present a potential hazard when consumed.