June/July 2022 Issue

Fermented Foods: The Rise of Sourdough Bread
By Joanna Foley, RD
Today’s Dietitian
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.

Fermentation Process
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.”

Health Benefits
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.

[Recipe]

Homemade Sourdough Bread Recipe

To begin making sourdough bread at home, clients will need a sourdough starter. They can search online for a recipe that sounds practical. Making one from scratch can take about a week to achieve a ripe starter that’s ready for use in baking bread. Alternatively, clients can obtain a starter from a friend or buy one from a fermentation store or bakery that sells it.

Active prep time: 30 minutes
Cook time: 50 minutes
Total time: about 1 1/2 days

Equipment Needed
Jar with lid
Large bowl
Medium-size bowl or jar
Round, 7-quart Dutch oven with lid
Oven
Food scale
Large spoon
Scoring tool or sharp knife
Countertop for hand kneading

Ingredients
Bread flour and/or other high-quality
flours such as rye and whole wheat.
Do not use gluten-free flours.
Water
Sea salt
Ripe sourdough starter

Directions

To prepare the dough:
1. Build up the levain. In the morning (before 9 AM), add 30 g ripe sourdough starter, 100 g bread flour, and 100 g water to a medium-size bowl or jar. Mix well with a spoon, then lightly cover it with a towel or cloth and let it sit and grow at room temperature to proof for about 7 to 8 hours. In the afternoon (around 3 to 4 PM), the levain should be ready for use. A simple test to determine whether the levain is ready is to take a small piece from it and see if it floats in a glass of water. If it does, it’s ready for use. If not, it needs a bit more time.

2. Take 200 g of the levain and add it to a large bowl, discarding any extra. Then add 600 g bread flour and 400 g water to the same bowl and mix well with a spoon. If desired, use different types of flour in this step, as long as the total amount of flour is 600 g. The flour mixture will be sticky and clumpy. When the mixture is well combined, let it sit for 45 minutes at room temperature.

3. After 45 minutes, add 10 g sea salt to the bowl and a small splash of water to dissolve the salt. Then, transfer the dough to a clean and lightly floured surface and knead the bread by hand for 8 to 10 minutes, stretching and folding the dough while kneading it.

4. Place the ball of dough back into the bowl, cover it loosely with a cloth and let the bread sit to proof and ferment for 3 to 4 hours at room temperature.

5. After 3 to 4 hours, knead the dough again for a few minutes to knock the air out and shape the dough into a ball. Line a bowl with a cloth, and lightly dust the cloth with flour to prevent sticking. Place the dough ball in the bowl, and lightly cover the bowl with a separate cloth.

6. Place the bowl in the refrigerator, and let it sit overnight.

To bake:
1. The next morning, preheat the oven to 500˚ F, and place a Dutch oven inside the oven while it’s preheating, for about 30 minutes.

2. Take the dough out of the refrigerator and place it on a large piece of parchment paper, then score the top. Remove the Dutch oven from the preheated oven, place the bread dough with the parchment paper into the Dutch oven, and cover it with the lid of the Dutch oven.

3. Place dough and Dutch oven back into the oven and turn down the oven temperature to 425˚ F.

4. Bake bread for 25 minutes. After 25 minutes, remove Dutch oven lid and bake for an additional 25 minutes, for a total of 50 minutes of baking time.

5. Take the bread out of the oven, and let it cool for at least 45 minutes before slicing and eating.

6. Bread is best on day 1 but will keep up to 3 days at room temperature. It may be ideal to toast the bread on days 2 and 3. You can freeze the bread for up to 1 month if needed, then defrost it at room temperature before using. Store bread in a large plastic bag, bread box, or other airtight container.

Tips to Feed and Maintain a Sourdough Starter
Feed the starter two to three times per week and keep it in a large jar with a lid, such as a Mason jar. To feed, take the jar with the starter out of the refrigerator in the morning and mix in 2 T of water plus 2 T of bread flour. Then, leave the starter out at room temperature for the majority of the day and put it back in the refrigerator at night before bed. Leave the starter in the refrigerator until the next feeding, about three to four days. Keep in mind that the bigger the starter gets, the more water and flour it will need to be fed, and always feed it in equal proportions of water and flour.

If you’re not using the starter fast enough (ie, it’s getting too big), discard half of it so it doesn’t need to be fed as much water and flour. The good news is a sourdough starter is resilient. If it isn’t fed for a day or two longer than what’s recommended, it usually will revive itself in almost all cases. If the starter starts to collect liquid on top, this is a sign it hasn’t been fed in a while and is in danger of spoiling. Simply drain off the liquid and feed the starter as soon as possible. A sign that a sourdough starter has spoiled and needs to be thrown away is the presence of moldy streaks on the top.

 

References
1. Resendes S. Restaurant menu trends: how Covid changed restaurant offerings in 2020. Upserve by Lightspeed website. https://upserve.com/restaurant-insider/restaurant-menu-trends/. Published November 12, 2020.

2. Nielson-Stowell A. Retail sales trends for fermented food and beverage. The Fermentation Association website. https://fermentationassociation.org/retail-sales-trends-for-fermented-food-and-beverage/. Published November 24, 2020.

3. Nielson-Stowell A. Bubbling over: pandemic sourdough. The Fermentation Association website. https://fermentationassociation.org/bubbling-over-pandemic-sourdough/. Published February 22, 2022.

4. Catzeddu P. Sourdough breads. In: Varelis P, Melton L, Shahidi F, eds. Encyclopedia of Food Chemistry. Cambridge, MA: Elsevier; 2019.

5. Dees J. The sourdough microbiome. American Society for Microbiology website. https://asm.org/Articles/2020/June/The-Sourdough-Microbiome. Published June 26, 2020.

6. De Vuyst L, Neysens P. The sourdough microflora: biodiversity and metabolic interactions. Trends Food Sci Technol. 2005;16(1-3):43-56.

7. Lau SW, Chong AQ, Chin NL, Talib RA, Basha RK. Sourdough microbiome comparison and benefits. Microorganisms. 2021;9(7):1355.

8. Gabriele M, Sparvoli F, Bollini R, Lubrano V, Longo V, Pucci L. The impact of sourdough fermentation on non-nutritive compounds and antioxidant activities of flours from different Phaseolus vulgaris L. genotypes. J Food Sci. 2019;84(7):1929-1936.

9. Rizzello CG, Portincasa P, Montemurro M, et al. Sourdough fermented breads are more digestible than those started with baker’s yeast alone: an in vivo challenge dissecting distinct gastrointestinal responses. Nutrients. 2019;11(12):2954.

10. McNamara L. Sourdough processing and FODMAPs. Monash University website. https://www.monashfodmap.com/blog/sourdough-processing-fodmaps/. Published November 8, 2017.

11. Nionelli L, Rizzello CG. Sourdough-based biotechnologies for the production of gluten-free foods. Foods. 2016;5(3):65.

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.