The broken portion is more easily invaded by certain storage pests. Foreign matter Dilution of the prime product by foreign matter reduces the value, and also may affect handling and processing. Elements from all three subclasses may render the grain unfit for consumption. Potentially the greatest threat to health probably is from micro-contamination with the bacterial products of poor sanitation, and with toxins and chemical pesticide residues. Contamination not only has direct food hygiene implications but also indirect ones, as invading micro-organisms may produce toxins under certain conditions which may lead to acute or chronic illness.
Grains differing in size and other characteristics affect processing potential.
Whilst preference for a particular variety may be influential nationally or regionally, internationally-traded grain is recognised usually by grain type rather than by variety e.g. yellow or white maize.