Hello again, my name is Professor Julien Sprenger, senior head microbiologist at Highfield University.

Today we will look at the fascinating world of micro-organisms. Bacteria are a micro-organism. They are a biological food hazard which can lead to food poisoning.

Micro-organisms are everywhere but you can’t see them. So small, you need a microscope.

As you can see, microscopic. Tiny. Very, very small. Some micro-organisms are good for you. Some micro-organisms are not.

Remember, one type of micro-organism is called bacteria. Bad bacteria are called pathogens. Pathogens produce poisons. Poisons are also called toxins. You can’t smell or taste toxins. But they can give you food poisoning.

So! What do bacteria need to grow? There are four things to look at.

First, time and temperature. Foods which encourage the growth of bacteria are usually high in protein, such as meat, fish and dairy products.

Here we see what happens to food over time and when not refrigerated. Here we see the before. And the yoghurt. And what happens after several days. As we can see, the micro-organisms in this food have multiplied.

Also, moisture is needed. Moisture is water in the food. Micro-organisms, such as bacteria, require moisture in order to grow. Protein foods and high risk foods all contain enough moisture for bacteria to grow. Here we see what happens to bread after several days. The micro-organisms have multiplied.

So, remember, bacteria need four things to grow: food, moisture, time and temperature. Here we see a single Bacteria. In 20 minutes 1 bacteria has split into 2. An hour later, 2 have become many. This is called Binary Fission. In 10 hours, one bacteria can become more than 100 million! Fascinating!

Also, bacteria like a warm environment, human body temperature of 37C is the best! Most bacteria begin to die in temperatures over 63C. Temperatures above 70C will destroy most bacteria.

Here we see a cup of warm water and a cup of boiling water over 70 degrees Celsius. Let’s pretend this is bacteria. As we can see nothing happens. Let’s try to do the same with boiling water. See! Destroyed.

So remember, bacteria are not killed by low temperatures. They just slow down or stop growing, but they are not killed. To prevent micro-organisms growing, food should be stored at temperatures of 5 degrees Celsius or below. To kill bacteria, cook in temperatures over 70 degrees Celsius.

So! Keep food hot, above 63 degrees Celsius, and keep food cold, below 5 degrees Celsius and we stay out of the danger zone. The danger zone is between 5 degrees Celsius and 63 degrees Celsius. Micro-organisms such as bacteria grow best in the danger zone. Well, it’s time I finished for now. Until next time, goodbye.