What is fermentation?
The definition of fermented foods could be “the conversion of raw foods by microorganisms into new foods“. Fermentation served firstly as a way of improving shelf-life but it also enhances nutritional quality and palatability and provide metabolites, enzymes (e.g. lactase) and flavor components.
A lot of traditional foods are in fact made with fermentation around the world and as a consequence, we eat a lot of microbes everyday.
What are the different kinds of fermented foods?
Fermented foods have been popular for 10,000 years. Partly, because products like fresh yogurt, aged cheese, or spicy kimchi have aromas and flavors unlike any other foods. Another reason is the health benefits associated with many of these products. Wine, chocolate, and coffee, for example, are rich in natural antioxidants that promote heart health and fight disease.
However, for many consumers, it’s the live bacteria that matters most. That’s because many of the bacteria found in fermented foods are associated with gut health and other benefits.
But not all fermented foods contain live organisms. Beer and wine, for example, undergo steps that remove the organisms. Other fermented foods are heat-treated and the organisms are inactivated. Bread is baked and sauerkraut is often canned. So, while these foods may be nutritious, they do not have probiotic activity, unlike yogurt, kefir or any other fermented dairy foods with added probiotics.
We must also be mindful of the fact that a lot of fermented foods do not necessarily have any probiotic functions. By definition, probiotics must “confer a health benefit”, meaning that the probiotic must have been characterized and have clinical evidence of a health benefit. Cultures are not probiotic unless they have met this requirement. Therefore not all fermented foods can be qualified as probiotic, and not all probiotics take the form of fermented foods.
What are the health benefits of fermented foods such as yogurt?
Yogurt and fermented milks are part of the most significant sources of viable bacteria (1 Cup of Yogurt = 108-10 bacteria). Epidemiological studies have shown that yogurt consumption is generally associated with reduced risks of type 2 diabetes (T2D), metabolic syndrome, and heart disease, and improved weight management.
The live microorganisms present in these products are now considered responsible for many of these health benefits. Included are the yogurt starter culture organisms, Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus, as well as strains of Bifidobacterium and Lactobacillus added specifically for their probiotic properties. Fermented dairy peptides and especially yogurt-type peptides generally exerted greater anti-inflammatory effects than other dairy products. One study found that fermented milk eased symptoms of irritable bowel syndrome, possibly due to beneficial changes in gut bacteria that such foods bring. Other fermented foods appear to relieve the diarrhea that people often suffer from after taking antibiotics and the latest areas of research is on the microbiota-gut-brain axis, suggesting that probiotics and prebiotics could influence behavior. Studies show that yogurt can increase levels of serotonin, the “feel-good” neurotransmitter, making it a tasty way to help fight depression.
How do we explain healthy effects of fermented foods?
According to researchers, the transformation or change in the food brought about by microorganisms can explain the effects of fermented foods. More specifically, it’s probably the microorganisms that reach the gut and produce beneficial end products that are involved in these healthy effects. Lactic acid bacteria (LAB) are usually used in dairy fermentation. LAB produce several bioactive metabolites during fermentation, including bacteriocins (anti-microbial peptides that either kill other types of bacteria or prevent them from reproducing) and peptides. Bioactive peptides are released when proteins are broken down, either during milk fermentation or in the gut after eating fermented products containing LAB. These peptides have been linked with several health-promoting mechanisms, including lowering blood pressure and anti-clotting activities, anti-oxidant activity, and activities that modify the immune response. Bioactive peptides may also help to improve insulin sensitivity. Ingestion of LAB-fermented dairy products can modulate the microbiota that inhabits the gut, with potential benefits on health. Modern dairy fermentation techniques may bring about additional health benefits by adding probiotics and prebiotics. Another ongoing area of investigation for food scientists is to find out whether the method of delivering live microorganisms, otherwise known as the ‘food matrix’, matters for how the bacteria survive—and for how they contribute to health.