Question

How do stored grain gets spoiled?

Answer 1

Both abiotic and biotic factors damage stored grains.
Abiotic Factors
1. Moisture contents of Grains : Moisture content of Grains is generally higher than optimum 14%. Higher moisture content of grains increases their respiration, which heats the grains and reduces their keeping quality. Microorganisms, fungi and insects attack such grains.
2. Dampness and Humidity of Air : Dampness of godowns and humidity of air cause growth of moulds over and inside the grains.
3. Temperature : Temperature of 30${}^0$C and above is harmful to stored grains due to activity of microorganisms, insects, pests and activation of enzymes of the grains.
Biotic Factors
1. Rodents : Six rats consume food equivalent to an average human being. They damage 5-6 times more grains by cutting and contamination (by urine, hair and excreta).
2.Birds : Birds are often seen in large number around godowns. They are able to puncture bags and eat the stored grains. The birds also contaminate the stored grains with their excreta and feathers. Bird excreta often contains Salmonella; the bacterium causing food poisoning.
3.Insects and Worms : Insects and their larvae feed on. stored grains either internally (internal feeders like Pulse Beetle, Rice Weevil, Lesser Grain Borer) or externally (external feeders, Khapra Beetle, Rust Red Flour Beetle). They damage the grains, decrease their quality and cause contamination with webs, cocoons, excreta, dead remains and toxins.
4. Microorganisms : Bacteria, yeasts and mould attack stored grains and cause their rotting. Rotting brings about discolouration, loss of weight, bad odour and aflatoxin contamination of grains which also lose their ability to germinate.