During their journey from farm to consumer food commodities are likely to be exposed to a multitude of hazards that may lead to contamination by dust, dirt weeds, mechanical injury, physicochemical changes accelerated by heat, light, metal ions, contamination or spoilage due to microorganisms insects and rodents or biochemical changes brought about by enzymes that may be endogenous or contributed by the invading biological agents.
Food commodities are thus likely to undergo significant alteration. Even though the consumer reference is undoubtedly for farm fresh foods and farmers and traders have been striving to keep up farm fresh image of food commodities, the question remains how fresh?
Amongst food grains particularly oilseeds, which are seeds high in essential oils, the entry of weed seeds at harvest, especially if harvesting is mechanical, is a serious contamination of the weed seeds harbor toxicants like Crotolaria, Datura and Argemone for instance.
Not only fruits and vegetables but even seeds may undergo mechanical damage. In the case of high moisture commodities, this will most likely be followed by microbial infections and spoilage.
In fat rich commodities such as oilseeds and nuts, oxidative chemical changes are most likely to be catalyzed by exposure to air, elevated temperature, humidity, light and metal salt contaminants leading to rancidity.
Such oxidative reactions affect essential oils and oil bearing material adversely.
Microbial spoilage of foods and health hazards to consumers through bacterial and fungal toxins and enteric disease are especially associated with high moisture foods, animal foods in particular.
Moisture pick-up or loss depending on the relative humidity (RH) is another change that significantly affects the quality.
Many foods undergo staling on storage: bread and coffee are good examples. In many countries, where feasible, specifications have been laid down for food commodities indicating the tolerances with respect to changes to their quality.
Food Contaminants
