The Magic of Fermentation

by | May 31, 2020 | Food Microbiology, Food Science, Nutrition

Many of us have found ourselves having much more time at home than we’ve had in a while. This has led to us foodies going back to basics in our kitchens since we can no longer get our fix from brunch with friends at that new trendy cafe. The internet is abuzz with banana bread and sourdough culture-making – which I will proudly admit I have also taken part in. I mean did you even lockdown if you didn’t bake? And if you live in the current South African Modern Prohibition of the roaring 2020 pandemic chronicles you may have seen the sudden rise in interest of home brewing and winemaking. Pineapples and preservative-free grape juice have never been in higher demand! So what better time than now to explore the magic of food and fermentation?

The relationship between microorganisms and food is a long-standing one. Humans have been utilising their abilities to transform our foods by fermentation before we even understood why milk went sour. All the while also trying to keep them out of our food so that it remains safe to eat and lasts longer. Most of my favourite foods and beverages make use of some microorganism in their production – wine, coffee, cheese, olives, yoghurt and even chocolate. It’s no doubt that we owe a lot to these tiny organisms invisible to the naked eye. Most of the time we are unaware of them until your cheese starts growing fur or your nose is filled with acidic buttery aromas from that milk carton you forgot to put back in the fridge.

Fermented foods have recently come into the spotlight as research has illuminated the health benefits that they may hold. This has been prompted by an increasing interest in the health of the human digestive system. While the obesity epidemic pervades and overconsumption of highly processed food continues it is no surprise that dieticians and nutritionists are seeing more and more patients exhibiting a host of gut health-related issues. Ongoing research is also leading us to believe that gut health is a good indication of overall health with some studies even seeing connections between gut health and mental health. This makes sense because the gut deals with everything one consumes and therefore forms one of the first lines of immune defence. With all that in mind what exactly is fermentation and why does it matter to our gut?

Fermentation can be defined as the process whereby some microorganisms – usually bacteria, yeast and moulds – feed on the macronutrients present in foods producing specific metabolites. These compounds produced are responsible for the complex flavour and aroma development in fermented food products as well as certain health-promoting effects in the gut. There are three basic types of fermentation named after their end products – lactic acid fermentation, ethanol fermentation and acetic acid fermentation. In food products, it is often a combination of the different fermentation types that result in such a product but below is a basic list of the principle fermentation types involved in their production.

In some foods, microorganisms are responsible for making them edible. For example, olives when harvested fresh from the tree are unbelievably bitter until the bacteria naturally present, Lactobacillus plantarum, spontaneously ferments the bitter phenolic compounds transforming them into the complex flavours we are familiar with. Foods like cassava contain certain antinutrients such as phytate – which forms complexes with essential micronutrients like iron and zinc making them unavailable for absorption by the human body. Cassava also contains cyanogens, which transform into the toxic chemical cyanide. Fermentation of cassava with lactic acid bacteria is one method used to break down these antinutrients thereby rendering it safe to eat. Other than the fermentation that occurs to produce our beloved glass of wine or favourite beer, fermentation also takes place inside our digestive system by way of our own colony of gut microflora. Prebiotics is the term used to describe foods that act as fermentable substrates for the beneficial microorganisms called probiotics present in our gut. Most of the time these prebiotics are forms of fibre which we lack the ability to digest as we cannot produce the enzymes necessary to do so. The microflora in the gut, however, produce the enzymes required to break down these prebiotic foods and thereby produce metabolites that our bodies can absorb and utilise. Some of these metabolites include things like short-chain fatty acids (SCFAs) which have a host of health-promoting functions in the body like modulating the immune system, feeding colon cells and reducing the pH inside the gut making it difficult for pathogenic bacteria to survive.

Fermented foods with live bacteria in them like sauerkraut or kimchi act as transport vessels for probiotics to make their way into the digestive tract. Many of these species that ferment our foods are similar to or the same as those found in the intestinal tract. This is why when we eat them there is reasonable cause to believe that these foods should exhibit the same health benefits as those species currently present inside the gut. Below is an infographic that summarises the journey of fermented foods to the colon. The food along with prebiotic substrates such as polyols and non-digestible polysaccharides, the live probiotics responsible for carrying out fermentation in the food, and the resultant metabolites from said fermentation such as lactate and carbon dioxide enter the body. Digestion occurs where some of these components are broken down and those surviving probiotics and undigested prebiotics finally make their way into the colon. Here, the resident microflora attacks the prebiotic substrates and produces metabolites like SCFAs, gaseous compounds, vitamins and antioxidants.

Image based on infographic presented in van Hylckama Vlieg JE, Veiga P, Zhang C, Derrien M, Zhao L. Impact of microbial transformation of food on health – from fermented foods to fermentation in the gastro-intestinal tract. Curr Opin Biotechnol. 2011;22(2):211‐219.

Artwork Credit: Nikita Gemeliaris 

In the coming weeks we will be exploring the magic of food and fermentation with specific interest in the science behind some of the processes used to produce food products and specifically the role it  plays in human nutrition. However, if this article has you wanting to know a bit more before then, we would recommend having a squiz through the below reading material or giving some of these podcasts a listen.

Further reading, listening and sources used:

  • For a little more in depth reading on probiotics –
  • If you prefer to listen instead –  ,
  • van Hylckama Vlieg JE, Veiga P, Zhang C, Derrien M, Zhao L. Impact of microbial transformation of food on health – from fermented foods to fermentation in the gastro-intestinal tract. Curr Opin Biotechnol. 2011;22(2):211‐219.
  • Marco, ML, Heeney, D, Binda, S, Cifelli, CJ, Cotter, PD, Foligné, B, Gänzle, M, Kort, R, Pasin, G, Pihlanto, A, Smid, EJ & Hutkins, R 2017, ‘Health benefits of fermented foods: microbiota and beyond‘, Current Opinion in Biotechnology, vol. 44, pp. 94-102.