Modes of Food Spoilage

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Modes of Food Spoilage
Introduction:
Food spoilage is any change that leaves the food unfit for human consumption. Spoilage of food e.g fruits occur in such a way that when a fully ripened fruit is allowed to expose to such conditions of temperature and moisture that allows the deterioration and proliferation of microbes the fruit is just at the edge of being spoiled. If such conditions persist, microbial growth occurs and the texture of food becomes soft and its colour has also been changed. It becomes unfit for consumption and is actually spoiled. Different types of foods e.g meat/fish, fats and oils etc spoil in different ways. In this article, the different modes of food spoilage will be discussed.
Mode of spoilage of stable foods:
Stable foods such as wheat, cereals, grains despite they are most stable ones but they are even spoiled by;
Insects
Rodents
Sometimes birds
Insects eat the grains partially and leave the damaged grain.
Rodents eat the grains and leaves excreta on them. The foods destroyed by rodents are more harmful to human health.
Birds in the same way consume the grains and leave the excreta on them. Such grains are also unfit for human consumption.
If in the storage place of grains, there is high humid condition, the grains absorb moisture that promotes the microbial growth such as bacteria and moulds; in them and renders them deteriorated or spoiled.
Spoilage of the semi-perishable foods:
The semi-perishable foods such as potatoes, onions and similar commodities are usually stored in refrigerators. These foods are spoiled by insects and rodents that bring loss in weight and quality of food. When they are stored in unfavourabe conditions, they may lose moisture and shrink in size and weight. Bacterial soft rot (caused by Eriwina carotovera) and black mould rot (by Aspergillus niger) are common types of spoilage in potatoes, onions and garlic.
Spoilage of perishable foods:
The ripening process in fruits and vegetables if left uncontrolled leads to their deterioration and spoilage. In fruits and vegetables, their structure is maintained by a hardening material that is protopectin. This material is changed to dissolved substance that is pectin, when these commodities are spoiled and deteriorated.
Mechanical damage to these commodities is caused by the attack of insects, rodents or birds leads to enzymatic deterioration and contamination. Milk and meat are spoiled by the microbes either naturally present or entered from outside. Meat will give off colour and milk will curdle. Fish undergoes deterioration due to microbes present in gut.
Spoilage by Autolysis
Autolysis: Autolysis is the self-destruction of food and refers to deteriorative changes occurring from within the food. Autolysis in foods is caused by the interactive relation of chemical substances within the foods or by enzymes. Autolysis may occur in the form of:
Auto-oxidation in fats and oils:
Short-wavelength induces auto-oxidation in lipids through the formation of lipid radicals which further form the lipid peroxy radical and lipid hydroperoxides. It usually starts with the uptake of oxygen by polyunsaturated oils and fats to produce compounds such as peroxides. Peroxides react the environmental hydrogen and from hydroperoxides. When hydroperoxides are formed to a harmful level, they tend to produce odorous compounds such as aldehydes, alcohols, acids and ketones. These products are the breakdown components of hydroperoxides that are responsible for off-smelling and off-flavour. Such type of signs are present in oxidized oils and fats, in which oxidative rancidity is accelerated by metals and other factors such as copper, light and high temperature.
Changes in meat colour:
When the meat is exposed to oxygen, some deteriorative oxidation reaction occurs and there is the off-colour development in it. Muscle myoglobin that is present in blood, in its deoxygenated form is purplish in colour but changes to oxymyoglobin on oxygen exposure. So, when the meat is exposed to oxygen it becomes bright red due to the formation of oxymyoglobin but later on, on the further and prolonged exposure of oxygen oxymyoglobin changes to metmyoglobin that is brown in colour.
Spoilage of Fish meat:
The spoilage of fish meat is caused by the microbes present in its gut. This process is accelerated by th enzyme action that is the enzyme-induced autolysis. The typical smell of the fish meat is due to a specific compound that is trimethylamine. It is produced by the enzyme action of bacteria on the trimethylamine oxide that is natural constituent of fish muscle. This causes the softening of fish tissues. Bacteria like Achromobacter, Vibrio and pseudomonas produce taints in fish by producing hydrogen sulfide and dimethyl trisulfide etc.
Conclusion:
So, in a nutshell there are different modes of food spoilage but only a few has been discussed in this article just to give overview mainly about the meat section of food. Foods are spoiled but with a litte care, they can be saved from spoilage and consumed as healthy food.

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