Yogurt, tangy in taste and creamy of texture, wasn’t always this delicious.
The magic of fermentation transforms milk of any mammal, a biochemical trick that not only charms the taste buds but prolongs shelf-life too. Fermentation also packs a nutritional punch, boosting vitamins and creating lively colonies of beneficial organisms.
Of course, fermentation isn’t just confined to milk. This slowest of culinary techniques is written across the menu of food and drink: bread, yogurt, sauerkraut, olives, pickles, vegetables, fruits, cheese, wine, beer, kimchi, kefir, kombucha and others. One common denominator in the recipes reveals a bit about fermentation science. In essence, carbohydrates are converted under anaerobic (without oxygen) conditions to alcohol, carbon dioxide and/or organic acids using yeasts or bacteria. No patent is
necessary, so go ahead and feel free to start up your own batch of yogurt or kombucha. This simple form of food processing has been valued by humans for thousands of years; some foods ferment naturally while others require a starter culture.
In the 21st century, microbes are formally getting their due thanks to modern techniques and rigorous lab work that clearly show the benefits extending far beyond gut health. Unfortunately, facts on the microbial makeup of many common fermented foods are limited. Further confusion arises regarding which numbers are best or even adequate when it comes to probiotics in fermented foods. Consumers hoping to take advantage of any benefits have few tools to help them make choices.
Organisms in fermented foods: what we know
• While lactic acid bacteria (LAB) dominate, other bacteria as well as yeasts and fungi can also be present.
• Actual numbers vary greatly, depending on methods, conditions and storage times.
• Heat of cooking kills many microorganisms such as when baking bread. Microbes may be filtered out as in beer and wine production. And pasteurization further destroys them as with canned sauerkraut.
• Consequently, many fermented foods and beverages are left with few remaining living microbes. Yet all is not lost. Bacteriocins and other valuable by-products are left behind by dead organisms. The theory of postbiotics suggests that these components may have
New data adds to the story
Last October at the Harvard Probiotics Conference, Robert Hutkins PhD from University of Nebraska spoke about the many functional effects of fermented foods as well as their potential in human health.
In an attempt to organize available data, Hutkins and his colleagues sought to identify the microorganisms that may be considered probiotic in commonly fermented foods. Fermented Foods as a Dietary Source of Live Organisms appeared online in Frontiers in Microbiology in Aug of 2018.
The researchers combed the literature for data on raw numbers of lactic acid bacteria and other bacteria in commonly fermented foods: cultured dairy products, cheese, fermented sausage, fermented vegetables, soyfermented foods, and fermented cereal products.
The review includes volumes of data attesting to the many good sources of live lactic acid bacteria, including species that reportedly provide human health benefits.
The team initially eliminated nearly three-fourths of the 400 published studies. The remaining 140 studies were surprisingly consistent even though they came from a half century of studies and from across the globe while using different methodologies.
Nine groups of fermented foods were reviewed. The research showed that many of the tested fermentation products contained 10⁵⁻⁷ LAB per gram, however origin and sampling times resulted in much variation.
In general, cultured dairy products consistently contained higher levels–up
to 10⁹/mL or g. These products specifically often promote their live cultures on the label. In the United States, a “live and active” seal created by the National Yogurt Association requires at least 100 million cells or cfu per gram at the time of manufacture. In Europe, the ESFA Panel requires the same number for a yogurt label to make a claim about aiding in lactose digestion. Australia has lower numbers.
For complete tables on specific foods, refer to the article. The following list is a brief summary.
Cultured dairy products: All of the yogurts from 8 different countries contained the yogurt culture organisms, S. thermophilus and L. delbrueckii subsp. bulgaricus, at levels ranging from < 10⁴
to 10⁹ cfu/g or ml. Frozen yogurt had similar levels of LAB to fresh yogurt LAB. In addition, kefir, cultured buttermilk, and fermented milk LAB were in the 10⁵–10⁹ cfu/g range.
Cheese: Microbial counts ranged from undetectable to very high with the highest levels found in Tilsit cheese. Aged cheeses including Grana Padano, Parmesan and Swiss Gruyere showed far fewer and often undetectable counts.
Fermented meats: Strikingly, sausages from the United States were generally lower in microorganisms than those from other countries. Smaller manufacturers appeared to produce sausages with higher counts.
Fermented vegetables: Results for fermented vegetables, including sauerkraut, olives, mustard pickles, pickles, and kimchi vary from no detectable live microbes to more than 10⁸ CFU/g and often more than 10⁷ CFU/g.
Traditional Asian fermented products: Miso, tempeh, fish sauce, and fermented fish too were quite variable; usually between 10³ -10⁴ CFU/ml.
Fermented cereals: African countries enjoy fermented porridges and gruels using pearl millet, millet, sorghum, and maize as starting grains; a range of 10⁵ to 10⁹ cfu/g was seen.
Beer: Several sour beer products from Belgium, such as lambic and gueuze, were included in the survey. LAB ranged from low to medium. Most beers, however, will have been filtered and are essentially free from microbes.
Kombucha: Little data exists for this fermented tea even though bottlers tout the live organisms. Bacteria and yeast counts in one study ranged from 10⁶ to 10⁷ cfu/mL
Evidence of health benefits associated with fermented foods
As with probiotics, many microbes seen in fermented foods may also have the capacity to survive digestion, reach the gastrointestinal tract, and ultimately provide similar health benefits.
Population studies have shown that consumption of fermented foods is associated with improvements of health status or reductions in disease risk.
For example, yogurt-rich diets link with lower risk of metabolic syndrome in older Mediterranean adults. And in some adults in Korea, kimchi consumption correlated with reduced incidence of asthma and atopic dermatitis.
Some evidence also points to improvement in biomarkers. Kimchi improved fasting blood sugar in overweight and obese adults in one study. In another, consumption of a fermented soybean paste improved plasma triglyceride levels in obese adults.
Fermented foods and probiotics
One caveat: fermented foods send potentially good organisms to the gut. They are NOT, however, “probiotic foods” due to the accepted differences in definition. Nevertheless, fermented foods share similarities with probiotic foods and should be consumed widely and often, according to public health experts.
Developing countries emerging from poverty often forget about traditional foods in their rush to adopt a western diet. Unfortunately, these regions could benefit greatly as fermented foods may play a role in decreasing diarrhea which kills an astounding number nearly one-half million children every year.
In South Africa, for example, yogurt, amasi, mageu and ting are widely consumed but rarely given to infants and small children. Amasi is fermented milk that tastes like cottage cheese and yogurt; mageu is a drink made from fermented maize; ting is fermented from sorghum flour.
Researcher Paul K Chelule and colleagues asked 33 caregivers in a rural community in Gauteng in South Africa about awareness and use of these products. The results were published as “Caregivers’ Knowledge and Use of Fermented Foods for Infant and Young Children Feeding in a Rural Community of Odi, Gauteng Province, South Africa.”
• Source of knowledge about fermented foods came from parents, grandparents and other relatives. No one received it from health workers.
• Attitudes about fermented foods were varied. Some thought fermented foods were nutritious but only for adults. Some thought fermented foods could be harmful for children (weight loss, phlegm).
• Accurate preparation methods were inconsistent.
Sadly, fermentation recipes are being lost to new generations who prefer the convenience and sweet taste of Western foods.
Public health ministries should reinforce the value of grandma’s recipes. Educating health care workers in their nutritious content as well as the preparation and safety of fermented foods is the way to go forward.
The International Probiotics Association (IPA) is a global non-profit organization bringing
together through its membership, the probiotic sector’s stakeholders including but not
limited to academia, scientists, health care professionals, consumers, industry and regulators. The IPA’s mission is to promote the safe and efficacious use of probiotics
throughout the world. Holding NGO status before Codex Alimentarius, the IPA is also
recognized as the unified “Global Voice of Probiotics” around the world.
Clare Fleishman MS RD bridges the gap between science and health across most platforms: major newspapers, magazines, books (Globesity), workshops, social media and websites. From corporate whiteboards to refugee schools in Egypt, Fleishman agitates for personal and public change. In 2010, she launched www.ProbioticsNow.com to share the cascade of new discovery in the microbiome. Always amazed at this “forgotten organ” Fleishman also creates white papers, blogs, videos and social media for the International Probiotics Association.