What are bacteria and how do they affect our food?
What are bacteria?
Before we can understand how bacteria affect your food, we need to define the term: what are bacteria?
How do we define bacteria?
Bacteria are single-celled microorganisms that can exist as independent organisms (free-living) or as parasites (depending on another organism to live). They are approximately 0.5 to 2 micrometers in size. A grain of sand is 2 millimeters in size. This means you could fit 1,000 bacterial cells into a single grain of sand. This means that we can only see bacterial cells through the microscope.
Aside from the microscope, bacteria form what we call “colonies” that have millions of cells that allow us to easily see the bacteria on a medium that is grown in the laboratory known as agar plates. This is the simplest method used to identify and view bacteria. We use this method to count how many bacteria are present, for example, on a swab from a cutting board. More than 300 colonies are considered dirty and contaminated.
These were one of the first organisms to exist on our planet, so they are very, very old and have co-existed with humans since the very beginning. There are millions of different types of bacteria, some good for you and some very dangerous to your health.
Where can you find bacteria?
Bacteria live in water, soil, plants, and animals. Bacteria are so prominent on Earth that they also live in some of the most extreme environments, such as the deep ocean, hot springs, and there is even evidence that bacteria lived on Mars.
For example, human-level bacteria grow in the gut, on skin, and in hair (including eyelashes). So much so, that recent research has shown that the composition of the different types of bacteria in the gut and on the skin is PLUS only a fingerprint.
Bacteria also grow and survive in the food we eat, raw meat and vegetables need to be cooked by design so that we as humans can consume these foods without getting sick from the bacteria that thrive in these environments.
There are two main distinctions for bacteria that we define as gram-positive and gram-negative bacteria.
We use this distinction to group the various types of bacteria based on their appearance and behavior. All commonly occurring bacteria fall under these two categories. Suffice it to say that we identify bacteria in the lab with a simple test that we use as a broad category to determine which bacteria we are looking at. This test is known as a Gram stain. This means that there are two main types of bacteria that look and behave differently from each other. With this method we can see the bacteria under the microscope.
This test also helps us see the shape of the bacteria. There are three forms, bacilli (rod-shaped), cocci (circular), and spirilla (corkscrew-shaped).
What do bacteria need to survive?
There are 6 elements in the environment that allow bacteria to grow and survive:
Temperature
moisture content
pH
nutritional content
Oxygen
Weather
Temperature
In general (with bacteria there are always exceptions) we see that bacteria can survive in very wide temperature ranges. Bacteria can live between 0 and 60 °Celsius (32 – 122 °Fahrenheit), however, at a level associated with humans, they grow best between 20 and 45 °Celsius (68 – 113 °Fahrenheit).
This is because the bacteria we are concerned about have adapted to our internal bodies to infect and contaminate our bodies. Therefore, the absolute best temperature is 37°C (98°F).
Humidity (Water Activity)
Bacteria can grow mainly in environments rich in moisture. In food, bacteria love moisture-rich conditions. Water activity refers to the amount of water available in a food product. Such an example would be cucumbers, there is a high availability of water in cucumbers, lettuce and celery (95%). Compared to dry spices (5 – 50%). Most bacteria need at least 80% water to survive.
nutritional content
Since we as humans need nutrients to survive, so do bacteria. High in nutrients, foods are a perfect source of nutrients for bacteria to grow. That is why we need to have very good hygiene standards in the kitchen. Food is an ideal environment for bacteria. The skin of humans and animals are also an example of a rich source of nutrients for bacteria. Bacteria require sources of carbon, nitrogen, phosphorus, iron, and a host of other minerals.
pH (acidity)
The level of pH or acidity also affects how bacteria grow and how effectively bacteria can survive in the environment. Bacteria in food range between 5 and 8 pH. This means that items like vinegar are unlikely to allow bacteria to survive.
Lemons are always a popular food when antibacterial properties are mentioned. In fact, the pH discourages the growth of bacteria, but it is not an important factor in killing bacteria that are produced by cross contamination. meats, spinach, and milk all fall within the ideal pH range for bacteria. Yogurt has a pH just below the ideal range and is generally considered less risky than milk because of this.
Oxygen
Bacteria can grow in both oxygen-rich and oxygen-poor environments. This means sealed and unsealed products. Therefore, vacuum-packed meals and foods are not without concerns. This also means exposing food to the environment and leaving food uncovered allows bacteria to grow.
Weather
The longer the bacteria are exposed to the above factors under their ideal conditions, the more the bacterial cells will become established. All of these factors are time dependent, and bacteria can multiply rapidly in 15 to 45 minutes.
Summary
We now know that bacteria can survive in temperatures between 0 and 65ºC (32 and 149ºF)
It grows best at 20 – 45ºC (20 – 113ºF).
They multiply rapidly in 15 to 45 minutes on these ranges.
Moisture-rich environments are favourable.
Can survive pH 3.0 – 7.5
It can survive in oxygen rich and poor conditions.
As you can see, bacteria are similar to humans in what they need to survive, therefore there are bacteria associated with humans and, as a result, bacteria found in the food we eat.
