By Dr Gal Winter, Senior Lecturer in Biomedical Sciences, UNE

What is fermentation?

Louis Pasteur, one of the founding fathers of Microbiology, coined the term ‘fermentation’ to describe a microbial form of life without oxygen. Fermentation, however, is not a process limited only to microorganisms. Humans perform fermentation routinely. When our muscle cells cannot get enough oxygen, we ferment glucose to generate energy. Furthermore, the human body is host to trillions of microorganisms, known as the human microbiome, which continuously carry out their unique fermentation processes within us.

There are different types of fermentations. Some microbes are capable of “alcoholic fermentation”, where they metabolise carbohydrates to produce alcohol and CO₂. Others are capable of “lactic acid fermentation” and metabolise carbohydrates to produce lactic acid, while some microbes are able to do both.

In the context of food, fermentations are biological processes that change food properties, while the microorganisms responsible generate energy in the absence of oxygen. Fermentation adds value to food by producing acids and flavour compounds, altering its texture and increasing nutrient bio-availability.

Nutritional benefits of fermented foods

Throughout history fermentation has increased the nutritional value of foods, supplementing them with increased amounts of vitamins, probiotics and prebiotics. Take the humble cabbage as an example. While being highly nutritious by itself, following the fermentation process it becomes a powerful superfood with many crowns attached to its name. In the traditional semi-vegetarian Korean diet, Kimchi – a fermented cabbage dish – is considered to be a significant source of vitamin B12, which otherwise is obtained mainly through the consumption of animal products. In fact, a study examining the longevity of Korean centenarians concluded that the inclusion of fermented foods in the semi-vegetarian diet was a crucial source of vitamin B12, which resulted in the maintenance of good health status.

In the western world, fermented cabbage can be credited for the safe return of voyagers and the discovery of new territories. Between 1500 and 1800, due to the lack of fresh food during long expeditions, 50% of voyagers developed a disease called scurvy, which was responsible for about two million deaths during that time period. Today we know that scurvy is caused by vitamin C deficiency, however back then it was connected to general nutrient deficiency. Once the correlation with nutritional deficiency was made, captains were given experimental foods to try and solve the issue through trial and error. One Captain, James Cook, was given fermented cabbage (sauerkraut) and sailed with 7,860 pounds of sauerkraut aboard the HM Bark Endeavor when he left England for the South Pacific in 1768. Cook returned home after three years without a single death attributed to scurvy – all thanks to a vigilant regimen of eating fermented cabbage!

Aside from the added nutrients, fermented foods are a rich source of pre- and probiotics , and as such are essential to support the human microbiome and support what is colloquially referred to as “gut health”.

We have about a hundred trillions of microorganisms in and on our bodies. This is an enormously large number to grasp, so to provide scale, this number is about 10 times higher than the number of human cells we possess. Scientists are just beginning to understand the significance of this data and the important role that these microorganisms play in many physiological processes from digestion and absorption, to brain behaviour and mental health. While there is no clear definition of a “healthy” microbiome, the general consensus is that the more diverse the better, with various disease conditions (diabetes, cardiovascular diseases, irritable bowel syndrome and others) characterised by reduced microbial diversity.

The vast majority of the human microbiome is located in the gut, mainly in the large intestine. The microbes there thrive on the food we provide them and shrivel if not provided with adequate nutrients, leading to reduced diversity. Adequate nutrients, aka prebiotics, are those that are not absorbed in the small intestine and reach the large intestine. These are largely known as dietary fibres. Unlike carbohydrates, fats and proteins, dietary fibres are not broken down by the human body and are left as a nutrient source for the gut microbiome. Dietary fibres are found in different plant foods and the inclusion of diverse fibres in the diet is considered to be a major contributing factor to a diverse gut microbiome.

With that in mind, let us revisit the example of the fermented cabbage. We find that in addition to the added vitamins and nutrients produced by microorganisms during the fermentation process, fermented cabbage contains high amounts of live bacteria as well as quality dietary fibres. This high concentration of probiotics and prebiotics strengthens our gut microbiome and promotes high microbial diversity and good “gut health”.

These advantages are not unique to fermented cabbage and hold true for all fermented plant foods. For this reason, as well as the great flavour and the joy that I take from watching the fermentation process in action, I make a conscious effort to include both fresh and fermented foods in my diet.