Bacteria are single-cell, microscopic organisms, with over 1 million able to fit onto the head of a pin, and still be invisible to the naked eye. They can be found everywhere, in soil, water, food, on people and in the air that we breathe. In most cases hundreds of thousands, or even millions of bacteria need to be consumed to cause food poisoning, however, there are strains which will cause illness if a relatively small number are eaten.
Many varieties are harmless or beneficial to humans as they thrive in the gut where they break down foods and absorb nutrients. Other bacteria are necessary for the production of foods such as yoghurt and cheese. Some as also essential for sewage treatment.
The harmful bacteria that cause food poisoning are known as Pathogens, they represent approximately 1% of known bacteria; other bacteria which causes food to rot are known as ‘Spoilage Bacteria’.
The Chain
To grow, bacteria need warmth, moisture, food and time, these four elements are known as the “Food Poisoning Chain”, to protect food, and your customers, a link of the chain must be broken.
Warmth
Most bacteria grow rapidly at body temperature (37), but can grow between 5c and 63c, this is known as the danger zone, more information on keeping food out of this danger zone by properly cooking and storing food will be available in a future blog.
Moisture
Most foods have enough moisture for bacteria to thrive, many dried or dehydrated foods will allow bacterial growth if they become moist. It is therefore essential to store foods such as these in a cool, dry place, and that they are used immediately after preparation. All dry foods such as flour and biscuits will remain safe as long as they are dry.
Food
Pathogenic bacteria grow well in high protein foods (poultry, meat and eggs). Foods that support the growth of bacteria and are ready to eat (such as cooked meat or dairy based desserts) are considered to be high risk, because if they become contaminated by bacteria, they will not be killed before the food is eaten.
Raw food that will be cooked or treated prior to being eaten are less of a risk because the bacteria should be destroyed by this process; foods that are eaten raw (oysters, sushi, etc) should also be considered high risk. Food such as cooked rice, pasta and cereals, whilst not being high in protein, are also considered high risk as they provide a warm, moist environment where bacteria can quickly multiply to dangerous levels.
Time
All bacteria grow by binary fission, they can do this every ten to twenty minutes in ideal conditions given the right circumstances; it is possible for one bacterium to grow to over one million in under four hours. To prevent this rapid multiplication, particularly in high risk foods, it is important that strict time and temperature controls are in place. We’ll be blogging some more about time and temperature controls at a later date.
Spores
Some bacteria can form spores, when the bacteria is under threat, such as from boiling, acid or alkaline conditions, they produce spores. Eating spores is not a health risk, however, when conditions become more favourable, they germinate and the resulting bacteria start to multiply once again.
Even when food has been dehydrated there is no guarantee that it will remain safe once rehydrated. Similarly even when food has been cooked, if bacterium have survived in spore form, they may be able to germinate and multiply again once food cools down.
Spores can be destroyed with high pressures and temperatures. Some spore forming bacteria can produce toxins that only cooking at extremely high temperatures can destroy; however, not all domestic cooking processes can reach sufficient temperatures to kill all bacteria, so all food must be treated with care even after cooking.
Remember - Deprive bacteria of one or all of their living needs, or destroy them through food processing. You can’t destroy all bacteria, so work to reduce them to a safe level.