Cross-contamination and how to control it?

Today, I’m going to talk about cross-contamination, how it can occur and how to control it and ultimately ensure food safety.

What is cross-contamination?

Cross-contamination is when bacteria get transferred from a contamination source (i.e. raw meat) to a high risk product (i.e. a chicken salad sandwich).

It can happen so easily in a kitchen. There are two main ways:

Direct cross-contamination

This is where the source of the bacteria comes into contact with the food. An example would be raw meat in a fridge physically touching cooked meat. Or raw meat juices dripping onto a ready to eat product (such as a cream cake).

Indirect cross-contamination

Bacteria are largely static so they either need to be in direct contact with the food or use other things to move them to food. This is called indirect cross-contamination and is where bacteria use a ‘vehicle’ to get onto food. For example: hands, knives, utensils, chopping boards, cleaning cloths, door handles, switches, taps, surfaces, equipment, packaging, machinery and sinks.

In order to control cross-contamination, it is useful to know a bit more about bacteria and where they come from. Let’s take a closer look now.

What are bacteria?

Bacteria are single-celled living organisms that are too small to be seen without a microscope. The bacteria that can cause food poisoning and foodborne illness are known as ‘pathogenic bacteria’.

Where do bacteria actually come from?

Bacteria can be found in many places. This includes the intestines of animals, and they are just naturally present in the environment and in the soil. Here are some of the main places that bacteria can come from:

• Raw foods- including raw meat, eggs, poultry, fish and fruit and vegetables
• Pests and pets- bacteria can be found on their fur/ bodies and also in their faeces and urine
• Rubbish- if not disposed of and handled correctly, rubbish can cause bacteria to spread onto food and it may also attract pests
• People- you may be surprised to learn that we as humans carry large amounts of bacteria in our intestines and they can come out in our faeces. Bacteria are also present on our skin and hair and in our ears, nose and throat. Our clothes may also be a source of bacteria.
• Dirt and dust- bacteria can be carried in the air on dirt and dust and may land on food in this way
• Surfaces and equipment- improper cleaning and disinfection of surfaces and equipment may result in bacteria being present
• Soil- bacteria naturally occur in the soil therefore bacteria could be present in the soil that may be present on unwashed fruit and vegetables
• Water- bacteria may be found in water that has not be subject to a proper treatment process. Foods such as fruits and salad items could be contaminated if they are washed in dirty water

Now we know where bacteria come from, it’s useful to know the sorts of foods we must focus on protecting from bacteria. These are known as ‘high-risk’ foods and they pose a greater food safety risk. Let’s take a closer look now.

High risk foods

When it comes to bacteria and food, you may be wondering what type of foods we need to worry about. High risk foods are those which pose a greater food safety risk. This is because they will support the growth of bacteria. So when it comes to cross-contamination, we need to make sure we specifically focus on protecting high risk foods to ensure they do not become contaminated with bacteria.

High risk foods are those foods which are:

1. Ready to eat i.e. they will not be cooked or reheated so there will be no opportunity for bacteria to be killed
2. They are moist, that’s because bacteria need moisture to be able to grow
3. They are high in protein, that’s because bacteria favour foods which are high in protein

Some ways to control cross-contamination

It’s really important to understand the different routes that bacteria can take to transfer from a contamination source (i.e. raw meat) to high risk food (cooked and ready-to-eat foods). That way, you can take steps control cross-contamination and ultimately prevent food poisoning.

Here’s the key ways to control cross-contamination:

• Ensure that raw and ready to eat foods are separated at all times
• Use single use disposable or colour coded cloths for cleaning
• Ensure thorough cleaning and disinfection is in place
• Use separate sinks for hand washing, for washing food and washing equipment
• Use separate equipment for preparing raw and cooked/ready-to-eat foods such as colour coded utensils and chopping boards.
• Where possible, have prepare raw and cooked/ready-to-eat foods in separate areas.
• Follow current guidance in relation to the use of complex equipment. For example; if you vacuum pack foods you can’t use the same vacuum packing machine for both raw and cooked/ready-to-eat foods.
• Ensure that all food is covered / packaged adequately when not being prepared
• Ensure that premises are free from pests at all times
• Minimise the handling of food
• Reduce the number of surfaces that food comes into contact with
• Reduce the number of surfaces hands need to touch i.e. replace hand operated taps with sensor or knee/elbow/ foot operated taps.
• Ensure that you maintain high levels of personal hygiene and wash your hands regularly.
• Finally, an employer needs to ensure that food handlers are adequately trained, instructed and supervised.