Food Safety – Bacteriology – The Food Poisoning Chain

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. On a Food Safety basis, many varieties are harmless (or even 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.

If you have Food Safety  concerns, we can help you.

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.’ You can learn about these on our various Food Safety Training courses.

The Food Poisoning 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. Your food safety management system should help you to do this. If you understand the Food Poisoning Chain, then you can break it and improve your food safety performance.

Warmth

Most bacteria grow rapidly at body temperature (37°C), but can grow between 5°C and 63°C; 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 food safety blog article.

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 before being eaten are less of a risk because the bacteria should be destroyed by this process; foods that are eaten raw (oysters, sushi, etc.high risk) should also be considered high risk. Food such as cooked rice, pasta, and cereals, while 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 (splitting), 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, particular 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 in a later food safety article.

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 bacteria 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.

The Food Poisoning Chain: Remember – Deprive bacteria of one or all of their living needs, or destroy them through food processing. You can’t kill all bacteria, so work to reduce them to a safe level.

If you need Food Safety assistance, then contact us on 01509 550023