June/July 2022 Issue
Fermented Foods: The Rise of Sourdough Bread
By Joanna Foley, RD
Vol. 24, No. 5, P. 12
A few decades ago, people may not have been familiar with fermented foods. But they’ve seen significant growth in recent years, and demand doesn’t seem to be slowing down. Fermented foods saw an increase of 149% on restaurant menus in 2018, becoming the most popular menu item at the time, and they’ve continued to see record growth since.1 In 2020, the fermented foods category was worth a reported $9.2 billion and had grown 4% in the last year. However, fermented foods still represent only about 1.4% of the food and beverage market today due to the extreme variety and high volume of products.2
Kimchi, fermented sauces, and tempeh are leaders in the fermented foods category. Sake, plant-based meat alternatives, and miso had a combined annual growth of $75 million in 2020. Sake grew by 16%, and both plant-based meat alternatives and miso each grew by 26%.2 Other forms of popular fermented foods include kombucha, kefir, sauerkraut, yogurt, and sourdough bread.
Katie Sullivan Morford, MS, RD, a cookbook author, writer, and blogger at Mom’s Kitchen Handbook, says the increase in popularity of fermented foods is a combination of two factors. “First, is the growing interest in global cuisine. Fermented ingredients such as kimchi and miso are becoming more mainstream,” she says. “I’ve also seen an uptick in the use of yogurt in savory dishes as in the Middle East and Central Asia. Add to that the increasing awareness of the health benefits of fermented foods and you have a trend that looks like it’s here to stay.”
But unlike kimchi, miso, and yogurt, sourdough bread isn’t thought of as a fermented food, although awareness of this fact is growing. More consumers are learning about the unique health benefits of sourdough bread and showing more interest in buying and making it themselves at home.
The Lesser-Known Fermented Food
According to research by the Puratos Center for Bread Flavour, 52% of today’s consumers are now familiar with sourdough. Approximately 45% of consumers associate sourdough with “better taste,” and nearly 30% associate sourdough with terms like “rustic,” “healthier,” and “more natural.”3 Throughout the COVID-19 pandemic and times of quarantine, there was a significant increase in interest in making homemade sourdough bread. “Baking seemed to be a comforting way to cope, and folks were home to nurture sourdough starters and tend to rising loaves of bread,” Morford says. On social media, sourdough reached a massive peak in consumer engagement during the pandemic, and demand for sourdough bread in stores and restaurants also increased.
Despite increased awareness, most people aren’t familiar with how sourdough is made or the health benefits it can provide.
Sourdough bread is one of the oldest types of bread; it can be thought of as the original bread, estimated to date back to 3700 BC or earlier.4 Unlike other bread, sourdough bread isn’t made with traditional dry and active yeast, known as baker’s yeast. Instead, it undergoes natural fermentation by lactic acid bacteria and naturally occurring wild yeasts that contribute to its ability to rise and its signature sour taste. This process made sourdough bread an easy and versatile form of bread for people in ancient cultures, and it’s still used today.
All sourdough bread comprises two major components: a starter and a levain, also called a leaven. A sourdough starter is a mixture of beneficial bacteria and wild, natural yeast. The starter contains naturally occurring probiotics, and the live microorganisms that make up sourdough starters are responsible for the unique aspects of the bread, including its flavor and shelf life.
However, while scientists know that certain kinds of bacteria and yeast populate sourdough starters, they don’t know exactly which microbes compose the sourdough microbiome because each sourdough starter is unique, much like the human microbiome. According to the American Society for Microbiology, researchers have used different techniques to study the microbes in sourdough starters, discovering more than 50 species of lactic acid bacteria (mostly Lactobacillus spp.) and more than 20 species of yeast (mostly Saccharomyces spp. and Candida spp.) living in the starters.5,6
But this doesn’t mean the finished bread contains significant live beneficial bacteria. “While the sourdough starter does contain probiotics, they are burned off in the baking process, meaning the end result is not rich in probiotics,” says Jessica Levinson, MS, RDN, CDN, a culinary nutrition and communications dietitian based in Westchester, New York. Nevertheless, she says, “sourdough bread is a good source of prebiotics, which provide food for the good bacteria. That’s why sourdough is especially good for gut health.” One of the potential prebiotics present in sourdough starters is beta-glucan, but its presence may depend on the type of flour used in the bread.7
A sourdough starter is made by mixing together two ingredients: flour and water. After a few days, a symbiotic microbial community develops, which helps create sourdough bread products. A sourdough starter must be maintained with regular feedings of bread flour and water two to three times per week to keep it alive and active (See “Tips to Feed and Maintain a Sourdough Starter” below). Otherwise, the microorganisms in the starter will die off and fermentation of the bread won’t occur.
What’s more, a sourdough starter can be used indefinitely if properly fed and maintained. This allows for countless loaves of bread and other naturally leavened baked goods. Aside from making a sourdough starter at home, consumers also can obtain one from a friend or family member who makes sourdough bread or purchase one from a fermentation store or bakery.
The second major component of sourdough bread is the levain. This is an offshoot of a sourdough starter made of a mixture of fresh flour, water, and some ripe, well-fed starter. The combination of the starter and the levain, along with time to ferment and some salt for preservation and flavor, are what create the delicious sourdough bread products that consumers love.
Different varieties of sourdough bread can be made by using different types of flours (eg, rye, whole wheat, spelt). Other ingredients also can be added to the traditional dough recipe, such as cheeses and herbs, to provide different flavors.
Not all sourdough bread is the same, and many likely will notice a big difference between homemade and store-bought sourdough. Homemade sourdough bread uses a simpler recipe and generally is much fresher. It’s usually made of three ingredients: water, flour, and salt. Store-bought sourdough bread, especially the packaged form, likely comprises additional ingredients and preservatives to keep it shelf stable.
Wendy Jo Peterson, MS, RDN, author of Bread Making For Dummies, says, “Most store-bought sourdough bread has vinegar added to it to give it the sour taste, whereas a true sourdough is fermented for a long period of time, developing the sour flavor through fermentation. Reading labels is important if you’re looking for sourdough bread.”
Sourdough bread has many potential health benefits, including the following, that set it apart from other types of bread:
• It may be more nutritious than other bread. The exact nutritional profile of sourdough bread will vary depending on the type of flour used and the recipe followed. “The presence of probiotics in the sourdough starter leads to an increase in other nutrients in the baked product,” Levinson says. “The bacteria in the sourdough starter along with the fermentation process decreases phytic acid, an ‘antinutrient’ that can prevent nutrient absorption. As a result, the nutrients in sourdough bread become more available.”8
• It’s easier to digest. Research has shown that sourdough fermented bread is easier to digest than those made with baker’s yeast alone.9 This is especially beneficial for people with irritable bowel syndrome or other digestive disorders. Though sourdough bread is lower in gluten because of the fermentation process, it isn’t gluten-free. However, there’s much anecdotal evidence that people with nonceliac gluten sensitivity can tolerate sourdough bread better than traditional gluten-containing bread. Keep in mind, though, that people with celiac disease or a wheat allergy shouldn’t consume sourdough bread.
Moreover, traditional sourdough bread is a low-FODMAP food, which further sets it apart from most other traditional bread.10 The fermentation process reduces the content of FODMAP, carbohydrates that can be more difficult for some people to digest. Following a temporary low-FODMAP diet particularly benefits individuals with irritable bowel syndrome.
• It benefits blood sugar levels. The fermentation process of sourdough bread lowers the availability of starch, thus decreasing its glycemic index, or the rate at which it raises blood sugar levels.11 Sourdough bread has a score of 54 on the glycemic index, which is lower than traditional white bread.
Recommendations for RDs
Since sourdough bread is primarily a carbohydrate-containing food, consumers still should be aware of how much they consume. One slice of sourdough bread (depending on its size) is equivalent to about one serving of grains for the day. Healthy adults should eat about six servings of grains each day, with at least one-half being whole grains.12 Sourdough bread isn’t always made with whole grains, but it still can be enjoyed as part of a healthful diet.
“One suggestion is to seek out sourdough bread made with whole grains, for the obvious fiber benefits and increased levels of naturally occurring nutrients,” Morford says. “I also think it’s worth exploring sourdough bread for folks on a low-FODMAP diet. Slow-rise sourdough bread can be low-FODMAP friendly and is often a whole lot tastier and more nutritious than some of the other low-FODMAP bread on the market.”
Rosanne Rust, MS, RDN, author, content creator, and blogger at Chew the Facts, says, “I think RDs should always be helping clients make the best individual choices that fit their lifestyle. Since carbohydrate and grain foods have been shunned in the media in light of extreme diet trends, it’s important that the registered dietitian share the importance of balance and enjoyment in the diet, which includes a basic understanding of portions. Grain foods add enjoyment to the diet, are affordable, and provide fiber and B vitamins.”
In addition, dietitians should remind clients to buy sourdough bread only from trusted brands or retailers and ask questions about the ingredients when possible. “If the ingredients list contains more than flour, water, and salt, it’s not a true sourdough,” Levinson says.
And when clients start making their own sourdough bread, Peterson says, RDs should tell them to “give yourself a month of flops to get this process down. Sourdough is alive, and it is not treated like commercial yeast bread. Before you get into whole grains, master the white flour version of sourdough, then slowly start adding in whole grains and playing with how your bread responds. The more you do it, the better your bread and starter will behave.”
— Joanna Foley, RD, is a San Diego-based freelance writer and author of two cookbooks. Learn more about her writing services at joannafoleynutrition.com/press.
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12. Suggested servings from each food group. American Heart Association website. https://www.heart.org/en/healthy-living/healthy-eating/eat-smart/nutrition-basics/suggested-servings-from-each-food-group. Updated November 1, 2021.