Fermenting olives. Photo used with the permission of Prof. Maria Marco. Copyright, ISAPP 2019.
What are fermented foods?
Fermented foods have been consumed throughout human history by different cultures around the world. They are defined as foods created through the activity of live microorganisms—and they require a food ‘substrate’ like a vegetable, dairy product, or even a meat product, plus bacteria or yeasts that are either naturally present or are added in order to kick-start the fermentation. A huge range of fermented foods exist, from chocolate and coffee to yogurt, kefir, sauerkraut, and kimchi.
Fermented foods are always made with microorganisms, but some products are later heated or processed in different ways, killing the live microbes. This means shelf-stable products stored at room temperature, like jarred sauerkraut and pickles, do not contain live microorganisms. Another example is sourdough bread: the live cultures are present in the dough but they do not survive the baking process.
It can be difficult to know whether a fermented food has live microorganisms when you consume it, but the words ‘contains live cultures’ on the label are a good indication. Natural health food stores often have refrigerated versions of sauerkraut and pickles that contain live microorganisms. Cheeses are variable: some soft cheeses like chevre contain microbes, but others like cottage cheese receive a heat step, so microbes are inactivated. In contrast, cheddar and most other hard cheeses do contain live microbes. But long-aged cheeses, like Parmesan, contain fewer live bacteria, since many of them die during storage. Also, while most beer and wine products contain no live microbes, it is possible to find ‘cloudy’ microbrewery beers are not filtered or heated and still contain live yeasts and bacteria.
What can fermented foods do for health?
Popular interest in fermented foods has increased during the past decade, going hand in hand with advancements with microbiology and fermentation in the food industry. Scientists are actively studying the health benefits associated with the live microbes found in fermented foods. Many of the bacteria in fermented foods are associated with good digestive health and other benefits.
It is important to note that the microbes in fermented foods do not always qualify as probiotics. The definition of probiotics is “live microorganisms that, when administered in adequate amounts, confer a health benefit on the host.” In many cases, scientists have not characterized the types and amounts of microorganisms in a fermented food product, and therefore cannot test the microorganisms’ specific health benefits. Some fermented foods such as many commercial yogurt products do contain probiotics. These are usually listed on the label and they confer a scientifically demonstrated health benefit. Nonetheless, fermentation-associated microbes that have not reached the status of ‘probiotic’ may share many of the traits of known probiotic organisms.
More information on fermented foods
See here for an article in which ISAPP board member Dr. Bob Hutkins from University of Nebraska, Lincoln (USA) explains the difference between fermented foods and probiotics. The ISAPP FAQs page also has answers to commonly asked questions about fermented foods.
See this short video, featuring ISAPP board member Prof. Maria Marco, on sourdough bread and the microorganisms that help create it: