Imagine this: you are trying to adopt a balanced and healthy diet, however, you’re not just consuming all your nutrition from your meal; you’re also eating about 1.3 billion microbes – mostly bacteria, with a side of a few thousand yeasts and mould every day, yum?!

Although the bulk of the microbes we ingest bite the dust in the pool of our stomach acid, there are a number of harmful strains that are more than capable of making us ill.

Instead of living in fear, it’s important to understand these “little creatures” and what we can do to avoid them!

So what is microbiology?

Microbiology is the study of these “little creatures”, also known as microorganisms.

They refer to a number of biological groups and are represented in the flow-chart below.

In each “group”, the microorganisms can be further classified as shown in the table example below classifying different strains of bacteria.

Most of these microorganisms are ubiquitous, meaning that they can be found anywhere and even in the air that we breathe in.

Are all Microbes bad?

Our food products are a home to a variety of microorganisms both “good” and “bad”.

“Bad” microorganisms are also commonly referred to as pathogenic microorganisms and they are microorganisms that can cause diseases in us.

The presence of a pathogenic microorganism in your food does not immediately mean that your food is unsafe to eat. 

This is a typical growth curve for bacterial cells and the life cycle of a bacteria can be classified into four stages. 

Phases Description
Lag Phase Bacteria initially adjusts to the new environment and requires time before it’s able to replicate quickly.
Log Phase Bacterial cells start to replicate quickly via binary fission. Bacterial growth rate is at its fastest during this phase.
Stationary Phase This occurs when the number of cells that is produced is equal to the number of cells that die off. This occurs as the nutrients in the medium are depleting.
Death PhaseThis occurs when bacteria cells lose their ability to divide and when the number of cells that die is more than the number of cells that are replicated.

Microbial factors that make food unsafe

Microbial infection and intoxication are two major reasons why we get food-borne illnesses! 

Microbial infections happen when enough microorganisms have entered our system [1]. The minimum number of microbes required to initiate an infection in us is also known as the infective dose.

Bacterial Intoxication on the other hand refers to food-borne illnesses that are caused by the ingestion of preformed bacterial toxins in food.


The production of bacterial toxins is a result of pathogenic bacterial growth in our food. 

Factors influencing microbial growth in food

The intricate microflora in a food product is generally influenced by its extrinsic environmental conditions (i.e., temperature, relative humidity, etc.) and intrinsic composition of food (i.e., water activity, pH, etc.).

Extrinsic factors refer to factors that do not make up the food itself. These factors refer to temperature, relative humidity, and the gaseous environment. They are also related to the food processing procedures and storage conditions. More often than not, these are the conditions that we have a direct control over. 

The first extrinsic factor that we will be looking into would be temperature. When environmental temperature increases, the enzyme efficiency of the microbe increases, and this allows microbes to grow faster. 

Now what are enzymes? Enzymes are a class of proteins that are responsible for speeding up biochemical reactions in our cells. The faster the biochemical reactions within the microbe, the higher the microbial growth rate. 

However after reaching a certain temperature, enzymes will begin to denature (not function), causing a decline in microbial growth.  

Categories of Microorganisms Temperature Range

Psychrophiles Subzero – 20ºC (optimum temperature below 15ºC)Pseudomonas and Enterococcus genera
Pyschotrophs 0 – 20ºC (optimum temperature above 15ºC)
Mesophiles20 – 45ºC
Bacillus spp.
Thermophiles 55 – 65ºC Clostridium spp.