It is essential to understand the conditions that enable bacteria to multiply to levels that cause food poisoning; they are a combination of four main requirements.
· Food
· Moisture
· Warmth
· Time
Food
Like all living things bacteria needs nutrients. Although different types of pathogens can live on a range of foods, most prefer something that is both moist and high in protein, such a those listed above. These foods support bacterial growth even after they are cooked thoroughly and served cold later.
Moisture
Pathogenic bacteria need moisture to stay alive; they can not multiply on dried foods. However as soon as liquid is introduced to foods, such as dried eggs and powder milk, the reconstituted products provide ideal conditions for bacterial growth. In contrast, quantities of salt or sugar (in food such as savory biscuits and bacon, confectionary and jam) absorb the available moisture in the food, making it harder for bacteria to multiply.
Temperature
Most pathogenic bacteria multiply at between 5˚C and 63˚C. This range of temperatures is therefore called the danger zone. Ambient temperatures (room temperatures) are generally within the danger zone. The ideal temperature for growth is about 37˚C, which is also the average body temperature. At temperature colder than 5˚C most bacterial multiplication slows down or stops altogether. This is why refrigerators should be at 5˚C or colder. Even so most bacteria will survive cool temperatures and resume multiplication when conditions return to normal. Freezing makes most bacteria dormant (inactive), but they may not kill them. When frozen food is thawed away any surviving bacteria can start multiplying again. Cooking at high temperatures kill most bacteria, providing that the food is cooked long enough, as a guide food needs to be cooked at 75˚C for a minimum of two minutes, right though to the centre or thickest part of the product.
Time
Bacteria need time in the right conditions to be able to multiply. When these conditions are right they only need about 10 – 20 minutes to do so. One bacteria splits into two, then two becomes four, and four becomes eight and so on, it will not take long for there to be enough bacteria to cause food poisoning.
Other bacterial requirements
Levels of acidity can affect multiplication; vinegar has traditionally been used to preserve food by pickling. The presence of lack of oxygen also effects the multiplication.
Aerobes: - need oxygen to multiply
Anaerobes: - don’t need oxygen to multiply
It is actually a very basic thing to have proper food hygiene training on your employees who are handling food goods.
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