Microbes are all around us, in the air, on our hands and in food from the farm.
Usually, they are in small enough numbers so that they do not cause any harm. However, a single bacterium, given suitable conditions of warmth, air and moisture, can grow to many millions in just a few hours.
Microbes will grow quickly when they are in the right conditions; warm, moist, correct pH and a supply of food to grow on. Preservation tries to alter the conditions to slow or stop the microbe growth. When this is not possible, or convenient, preservatives may be added to stop the food from going 'off'.
Different microbes are sensitive to different types of preservatives and so a wide range of preservatives are in use today.
Most preservatives today are actually fungistatic in their action. That means they prevent the growth of fungi, moulds and yeasts. They have little effect on bacteria but using a combination of preservatives, with antibacterial properties, can give good all round protection. Food preservatives help to control the spread of bacteria which can cause life threatening illnesses such as salmonellosis or botulism.
Preservatives are commonly used in these foods:
- low fat spreads
- cheeses, margarine, mayonnaise and dressings
- bakery products
- dried fruit preparations
Are Preservatives Safe?
Food preservatives have to be safe for human consumption. They can stop the food-decay microbes from growing but must not not harm the cells of the human body. There are also maximum levels of preservatives allowed, so that high concentrations of preservatives in food are not permitted.
There is much concern about the increasing incidence of the phenomenon of resistance of bacteria to antibiotics. Over the decades in which preservatives have been used, there has been no need to increase the dosage to maintain their effectiveness. This suggests that the use of these substances has not resulted in the development of bacteria that are resistant to preservatives.