Causes of food deterioration and spoilage:
- Environmental Factors (infestation, oxygen, light and water)
- Enzymatic Activity
- Microbial contamination (mould, yeast, and bacteria)
Food deterioration and spoilage can be caused by a combination of various specific factors that are categorised into three main groups; environmental factors, enzymatic changes and microbial activity.
ENVIRONMENTAL FACTORS:
INFESTATION: Organisms such as insects and rodents can cause spoilage in food, eg; weevils in flour and the transmittance of bacteria by rodents.
OXYGEN: Majority of organisms need oxygen in order to develop, with the acception being anaerobes that grow with out oxygen.
LIGHT: Phototrophs are an example of an organism that use light as an energy source.
WATER: Too much moisture in a product will encourage the growth of organisms, in theory this means the more moisture/ water present, the faster the food will spoil.
OXYGEN: Majority of organisms need oxygen in order to develop, with the acception being anaerobes that grow with out oxygen.
LIGHT: Phototrophs are an example of an organism that use light as an energy source.
WATER: Too much moisture in a product will encourage the growth of organisms, in theory this means the more moisture/ water present, the faster the food will spoil.
ENZYMATIC ACTIVITY:
Enzymes are found in all varieties of meats, fruits and vegetables. Even when foods are harvested or slaughtered the enzymes within them continue to work, causing over-ripening and the decomposition of food tissues to occur, eventually leading to the destruction of the food.
Not all enzymatic action is negative, we require enzymes in order to simply eat our beautiful ripe juicy fruit and vegetables daily. Slowing down or stopping the enzymatic actions in food is much easier than trying to stop microbial contamination. It is between the temperature range of about -8 to 49*c that enzymes are most active, however they can be destroyed at temperatures above 60*c. The cooler the temperature the more the enzymatic actions are slowed down, this is why fruit will last longer in the refrigerator then in a fruit bowl on the table. Most enzymatic action also requires moisture to occur. When foods are stored at 10% moisture or less, there is not enough moisture for most enzymes to be active, slowing their effects on foods. |
MICROBIAL CONTAMINATION:
YEAST:
Yeast are tiny organisms that cannot be seen by the naked eye, these organisms multiply at an extremely rapid rate and cause the fermentation of foods. This is done by them acting on certain components of perishable foods such as juices. During this fermentation, the sugars within the food are broken down to form carbon dioxide and alcohol. This is why foods with a higher sugar content such as honey and jams are more likely to be spoiled by yeasts.
MOULD:
Mould is easily seen by the naked eye, it is in the form of threads developed on perishable foods. They contain spores; these spores can be easilt spread through the air or via contact to start a new growth on another perishable item. Once moulds find themselves a favourable environment they will germinate and produce a growth, this growth is of a fluffy texture and can range in colour from blue, green, red, orange or any colour imaginable, it simply depends on the variety of mould. Most varieties of moulds are not harmful to humans; in fact some varieties of cheeses rely on mould for flavour. However there is a small portion of moulds that are capable of producing mycotoxins 'toxic materials', aflatoxins is an example of this and will cause illness.
BACTERIA:
Bacteria are unicellular organisms that are significantly smaller in size then both moulds and yeasts, they come under three classifications; coccus (spherical), bacilli (cylindrical) or spirillae (spirillar) on the basis of their shape as seen under the microscope. They also come in many different sizes, and the amount of food, acidity, moisture, temperature and oxygen they need varies. Their desired temperature range for development ranges between 20-53*c.
Bacteria are classified according to the temperature ranges that they need for growth:
1. A higher temperature than 45°C are known as thermopile, (e.g. in canning industry and milk processing plants).
2. Temperatures between 20-25°C are called Mesophiles.
3. Temperature less than 20°C are called psychrophites (e.g. in Refrigerator and in cold storages).
1. A higher temperature than 45°C are known as thermopile, (e.g. in canning industry and milk processing plants).
2. Temperatures between 20-25°C are called Mesophiles.
3. Temperature less than 20°C are called psychrophites (e.g. in Refrigerator and in cold storages).