The International Scientific Association for Probiotics and Prebiotics (ISAPP) has recently brought together a group of scientific experts to address the state of knowledge on fermented foods.
Kefir grains. Image Credit: International Scientific Association for Probiotics and Prebiotics.
Although there was a c considerable agreement on the fundamental microbiological mechanisms and health-related characteristics of certain foods and beverages, the debate on definitions triggered a sustained discussion. So what exactly is a fermented food?
The term “ferment” comes from fervere, a Latin word which means to boil. As per the Merriam-Webster dictionary, the verb “ferment” is described as “to undergo fermentation or to be in a state of agitation or intense activity”.
The word “fermentation” is defined as a chemical change with effervescence and also as an enzymatically mediated anaerobic breakdown of energy-dense compounds (for example, a carbohydrate to alcohol and carbon dioxide (CO2) or to organic acid).
In the field of biochemistry, fermentation is known to be an ATP-generating process, wherein organic compounds serve as electron donors and also as acceptors. At the industrial level, fermentation refers to the deliberate use of eukaryotic cells and bacteria to produce valuable products, like antibiotics or drugs.
As one can see, there are evidently several meanings indicated in the words “ferment” and “fermentation.” Scientists add to this by specifying how those terms apply to foods.
As the ISAPP panel started to consider the definition of fermented foods, it soon became evident how hard it can be to reach an agreement. Although several panel members shared analogous scientific skills and academic backgrounds, it took many rounds of discussion and also the consumption of fermented foods and beverages along the way to reach a consensus on the definition.
Ultimately, the panel defined fermented foods and beverages as being “foods made through desired microbial growth and enzymatic conversions of food components”.
Such a definition is very particular by requiring enzymatic processes and microbial growth for making those kinds of foods. The activity of the endogenous enzymes from the food components or enzymes introduced to the food is inadequate for a food to be considered as fermented.
Likewise, foods made by simply adding vinegar or “pickling” must not be named fermented. While the definition recognized the crucial roles of microbes for processing fermented foods, it does not need their viability or presence during consumption.
In contrast, the definition does not limit fermented foods to only those beverages and foods made through microbes using metabolic pathways that are implicit in the rigorous biochemical definition.
Kimchi and yogurt made using lactic acid bacteria that depend on fermentative energy metabolism are included as much as vinegar and koji, foods made using fermentation processes that use bacteria and fungi that carry out aerobic respiratory metabolism.
Every word in a definition should be meticulously calibrated. The best paradigm of this in the definition of fermented foods is the term “desired.” Food fermentations are different from food that is spoiled due to enzymatic activity and microbial growth and produce the required attributes. Other terms, like “controlled”, “desirable”, or “intentional,” may also be used to explain this meaning.
But those words also have caveats that not all fermented foods are produced “intentionally”, at least in the manner that they were initially prepared many years ago. Fermented food qualities may be “desirable” in certain cultures but not in others. Although some fermentation is “controlled”, others are spontaneous and need some human input.
The process of debating the definition with a panel of scientific experts was insightful because it allowed individuals to deconstruct their own individual assumptions of the word to reach a consensus on meaning and descriptions.
Armed with a definition, people can use a shared language to investigate fermented foods and to interact on the importance of these foods and beverages in their diets. There will also certainly be more “fermenting” of these definitions to enhance one’s understanding of the production and health that impact the characteristics of fermented foods for years to come.
Marco, M. L., et al. (2021) The International Scientific Association for Probiotics and Prebiotics (ISAPP) consensus statement on fermented foods. Nature Reviews Gastroenterology & Hepatology. doi.org/10.1038/s41575-020-00390-5.