Bacterial Growth in Food Safety

Watch this video to learn more about the ideal conditions to support bacterial growth. There are 4 things that you need to remember from this video.

Food, Warmth, Time & Temperature.

Time & Temperature

Remember from the video "Time & Temperature" are 2 of the 4 key conditions required for bacteria to multiply and survive. Understanding the key temperatures is very important in preventing the multiplication and survival of pathogenic bacteria.

Some bacteria can multiply every 10 minutes. That means 1 bacteria becomes 2 and then 2 becomes 4 .. so on and so on!

Below are the numbers from just one bacteria dividing every 10 mins for 2 hours. Imagine the numbers with many more bacteria present.

1 = 2 = 4 = 8 = 16 = 32 = 64= 128 = 256 = 512 = 1,024 = 2,048!!

This is why time is important in controlling the multiplication of bacteria in food. Reduce the amount of time food is kept in the danger zone will prevent the rapid multiplication of bacteria. The danger zone is 5-63°C.

The Germometer

The diagram below shows the key temperatures that are important for you to learn for food safety.

-18°C

This is the legal minimum-maximum temperature of a freezer. At -18°C and below pathogenic bacteria are dormant (sleeping) and do not multiply. At this temperature they are not dead they are just waiting for the right conditions to grow. (Remember warmth is one of the conditions bacteria need to multiply.)

TOP TIP: Checking your freezer temperatures in your work area twice daily will be part of your job role. When  frozen products are delivered,  the delivery vehicle will be checked to make sure it is at least -15°c (the door opening will make the freezer vehicle to about -15° but not the food). Most freezers onboard have alarms that alert when the temperature is below -18°C.

0°- 5°C

This is the legal temperature range of food in the fridge. The cold of the fridge slows down the rate at which bacteria will grow. We probe food in the fridge to make sure the core temperature is 5°C or less. However, it is ok if the digital display for the fridge reads 0°- 8°C. This takes into account the opening and closing of the door.

TOP TIP: To avoid cross-contaminating when probing your food in the fridge use a gel pack to probe instead. These are widely available and sit in your fridge all the time to allow you to check temperatures safely. Alternatively use a bacterial wipe on the probe before and after probing to avoid cross-contamination. 

Again the delivery vehicles of chilled food are checked and must not be over 8°C so you can be sure the food is safe. All your food fridges in galleys, behind bars, crew mess and pantries need to have temperatures checked twice daily and recorded.

Again fridges on board have alarms that alert when the temperature is below 5°C.

It is important to note that ship food deliveries once accepted are often stored in a large central walk fridge and freezers. The food may then be moved elsewhere on the vessel to other preparation areas or galleys. The transfer time is just 15mins! Food then must be stored in the fridge or freezer again or prepared quickly and cooked or defrosted quickly, prepared and cooked.

5°- 63°C:

This is the danger zone or high-risk zone. This is the temperature range where bacteria multiply rapidly. The most rapid multiplication occurs between 20°-50° Think about the body core temperature of around 37°C so once eaten the temperature is perfect. High-risk food (ready to eat) or raw food to be cooked must be kept out of this zone. So keeping preparation times to a minimum is important before cooking thoroughly or putting food back in the fridge. Food kept in the danger zone for 2 hours or more MUST be thrown away.

If you think about a high protein dish that is prepared, then cooked in advance, cooled and then reheated. This dish has gone through the danger zone 3 times. This increases the risk of bacterial multiplication, so is it safer to cook and serve/eat straight away.

TOP TIP: Always label any ready-to-eat food (high risk) with the time of display if held within the danger zone. An example of this is a board with cold cuts of meat and cheese. At room temperature it can only be displayed for 4 hours then the food must be discarded. Areas most at risk on board are buffets without temperature control (Hot and cold) or food left in the crew mess outside of the fridge. Keeping the amount of food displayed out of temperature control to small plates and replenishing often is safer and will reduce waste.

63°C

At 63°C most pathogens are starting to die (just above the danger zone). This is not the cooking temperature but is a very important temperature to learn for holding hot food during service as there is very slow multiplication above this temperature. You can hold hot food that has beeb cooked to over 75°C for service in the crew mess or buffet stations above 63°C.  If you are hot holding food stir it frequently and probe test the core of the food every 90 mins to make sure it is above 63°C.

TOP TIP: If you are holding food above 63°C make sure you make a note of the time you start displaying it and check the core temperature every 90 mins. Do not top up with fresh food, finish what is there and then replace it.

75°C or above

This is the temperature most pathogenic bacteria are dead and are now at a safe level and the food is safe to eat. This is the minimum cooking temperature unless you cook to 72°C for at least 2 minutes.

100°C

Bacteria are killed at this temperature. This is the boiling point.

But it does not end there. Some pathogenic bacteria are very resilient and work hard to survive. They do this by forming spores. This is especially important to know when it comes to cooking, cooling and reheating food. 

What next?

To ensure you fully understand how time and temperature are important to food safety and food safety management complete the full Level 2 Food Safety at Sea Training on Seably. Get in touch to learn more.