Food poisoning and spoilage should be top of the agenda for anyone involved in food factory design. Here Zarina Mohd, process project manager at Integrated Food Projects, discusses the causes of food spoilage and different methods for ensure the safe consumption of food.
Food spoilage occurs mainly as a result of chemical reactions involved in the process of ageing and decay. Almost all of our food is produced by living organisms, and whether they are animals or plants, they are mainly composed of organic compounds. When a plant is harvested or an animal is slaughtered, many of the complex and carefully controlled chemical reactions involving these compounds cease to happen. However, enzymes will still be active and are able to continue catalysing reactions which can adversely affect the quality of the food.
What are microorganisms?
There are principally three main types of microorganism that are responsible for food spoilage – moulds, bacteria and yeasts.
- Moulds are a form of fungi, which produce spores, or seeds, that can be carried considerable distances by air currents. Most moulds require oxygen for development, and this is why they are usually found only on the surface of foods. Poisonous mycotoxins are produced by some moulds, and serious illness maybe caused if the affected foods are eaten. To ensure complete destruction of all moulds and their spores, sterilisation under pressure is necessary. Alternatively, the food may be heated to 70-80oC on two or more successive days so that any spores germinating between the heat treatments will be destroyed.
- Bacteria grow by absorbing simple substances from their environment and when they reach a certain size, split to form two new ones. In favourable circumstances this fission may occur every 20 minutes or so – in 12 hours one bacterium can provide a colony of some 1010 bacteria. Some bacteria will only grow in the presence of oxygen whereas others, known as anaerobics, will only grow in its absence. Bacteria grow best within a given temperature range and in their vegetative state. Bacteria, like moulds, can form spores, but all of them can be killed by exposure to a temperature near 100oC, however the heat resistance of bacterial spores varies from species to species and with the pH of the surrounding medium.
- Yeast can also form spores, but they are far less heat-resistant than mould spores and bacterial spores. Yeast can grow in quite varied condition, but the majority prefer acidic foods (pH 4-4.5) with reasonable moisture content. Most yeast grow best in the presence of oxygen between 25oC-30oC – yet some yeast can grow at 10oC and below. Yeasts and yeast spores are easily killed by heating to 100oC. Although they may spoil food, yeasts are not pathogenic, meaning they do not cause diseases such as food poisoning.
Viruses in foods
Food poisoning can be caused by viruses as well as by moulds and bacteria. Viruses cannot grow in food and they require a living host in which to multiply. Viruses are resistant to many food-processing and food-preservation techniques, and are not affected by chilling, freezing, ultraviolet light or acidic conditions. They are, however, destroyed or inactivated by heating and do not normally survive the temperature involved in normal cooking processes.
So how do we combat harmful microorganisms and viruses from infecting our food? Pasteurisation is the process of heating food, specifically liquids, to an exact temperature to slow microbial growth in food. Pasteurisation required rapidly heating the liquid to a specific temperature for a specified time, followed by cooling. This process kills the heat susceptible organisms and their spores. The time and temperature conditions depend on several factors, such as size, shape and type of food.
Sterilisation refers to the process of eliminating all forms of microbial life. Sterilisation is not limited to only liquids, but can also refer to solid surfaces, fluids medications, etc. Sterilisation is done using various methods such as applying heat, irradiation, chemicals and high pressure.
Whether a food factory is producing vegetable or meat based products, ensuring that the food is safe and up to the relevant food safety standards is of the upmost importance, I hope this blog provided a little insight into what causes food spoilage and the different techniques undertaken to combat them.
For more information on food spoilage and microorganisms, speak to our team today.
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