With the cold weather these days, one pandemic trend is still keeping people’s homes warm: sourdough baking.
The process of making bread with live fermented cultures has grown in popularity since March last year – mainly because the yeast shortage in the COVID-19 pandemic took other breads off the table, and because many people spend more time at the home spent, Benjamin Wolfe, studying microbial ecology and evolution in his laboratory at Tufts. (See “Nine Tips for Making Yeast.”)
‘It’s great during stressful times – it’s like a creature and you take care of it. It’s a fun distraction, and all the better if you get delicious bread, ‘Wolfe said. He recently published an article on the varieties of microbes in sourdough entrees in the magazine. eLife.
Liz Landis, a student in Wolfe’s laboratory and a first author of the eLife paper, agreed. “It’s such a meticulous effort and you really need to pay a lot of attention to it, and that may be why it’s revived a lot during COVID-19,” Landis said.
Jessica Ellis, N20, a researcher from the Vitamin K Laboratory at the Jean Mayer USDA Human Nutrition Research Center on Aging (HNRCA) at Tufts, said she only made leaven on weekends but extended her baking time during the pandemic .
“Once you start a loaf of bread, there are a few steps you only have to take a few minutes, but it’s a few hours apart,” said Ellis, who studies bacterial-produced forms of vitamin K. work from home during the week. ”
But what exactly gives sourdough its special taste? How do microbes transform bread and other fermented foods like kombucha and sauerkraut that are booming during this time? According to Wolfe, Landis and Ellis, according to mr. Wolfe, Landis and Ellis a great deal of misunderstanding – and much more to appreciate.
“People have been making leaven in North America for a long time,” Wolfe said. “It was really fascinating to see how much role it played in this very stressful time.”
The Fermentation Game
Although most people have heard of the fermentation of food, there is some hesitation about how to work on it safely.
“When I first started fermenting, some of my roommates were afraid to try it,” Ellis said. ‘But fermentation is one of the oldest methods of preserving and transforming food. Many foods contain fermentation in the processing that people do not realize – such as coffee or chocolate. ‘
Bread also does not immediately appear as fermentation – but according to Ellis it is one of the more straightforward foods that you can change in this way. “Some need more deliberate cultivation, and others are more spontaneous,” she said. ‘If you leave out milk, it’s just going to spoil – it will not become yogurt. But sourdough kind of works by itself. ”
The process begins with an appetizer, or a small amount of flour and water. Let the mixture sit for about 24 hours, then take a small portion of it and mix it with fresh flour and water. This is repeated every day for two to three weeks, and then the microbes are active enough to start the dough.
Yeast is more forgiving of mistakes than other fermented foods, making it ideal for beginners. “Sourdough starters are quite resilient. “If you forget to feed it, or add too much or too little flour or water, you can usually revive it without starting all over again,” Ellis said.
It is also more dramatic in its transformation. “It made both yeast and bacteria, which change the texture of bread, rise and make it sour, which I think is delicious,” she said.
But one popular claim about leaven has to be taken with a grain of salt, warns Ellis – the idea that it is necessarily healthier than other loaves. Some studies have shown that fermentation can reduce the levels of short-chain carbohydrates that are difficult for the small intestine to absorb, which will make sourdough more tolerable for people with irritable bowel syndrome, Ellis acknowledged. But other studies have yielded conflicting results; Plus, it is unknown whether reducing these carbohydrates would be clinically significant, she said.
“There is a lot of potential for fermented foods and a lot of enthusiasm around them, but as far as science is concerned, clinical trials for many of them are still pretty sparse,” Ellis said.
Ellis is now investigating the potential benefits of a nutrient in many fermented foods: manaquinones, which are bacterially produced forms of vitamin K.
This is important because leafy greens have previously been considered the most important source of nutrition for this vitamin. Ellis in particular investigated the effect of these vitamin K forms on the intestinal microbiota. “Measuring such food in the lab has piqued my interest in making sourdough,” Ellis said. “It’s fun to play with your food.”
Edible Petri dishes
Although most breads need yeast, only flour and water are needed. Microbes are already present in flour and they multiply when water is added.
“By mixing flour with water and constantly adding fresh flour, you awaken the dormant microbes,” Wolfe said. This collection of bacteria is ideal for a laboratory like Wolfe, which studies the cultures in fermented foods in the hope of better understanding the human microbiome.
“Essentially, it’s small edible petri dishes that people put on their counters to create microbial ecosystems in their kitchens,” he said.
Sourdough entrees are also ideal to study because people make them all over the world, Wolfe said. As microbial ecologists, his team is interested in how cultures differ from place to place. This is what their recent study, published in eLife.
“The idea is that in Boston and New England there may be unique microbes, yeasts and bacteria that you do not necessarily find in Europe or San Francisco or South America, and that the different microbes have the taste and quality of the sourdough,” said Wolfe. He points to San Francisco, whose leaven has the reputation of being better than other varieties.
“We wanted to gain insight into what microbes grow in people’s home fermentations, and to determine how these different microbes affect the way they smell, and how fast the dough rises,” Landis said. “It is important that bread makers, especially industrial bread makers, can refine their methods of sourdough making – but we were also more interested in the form of microbiomes and their implications for microbiologists.”
Wolfe and Landis tackled this question in partnership with the University of Colorado at Boulder and North Carolina State University. In 2016, they started using sourdough entrees from different resorts. More than 500 entrees arrived by mail. “They kept coming and coming. “We brought up these huge bins with parcels that smelled a little funny,” Wolfe said. “People started looking at us strangely.”
Landis loved to smell all the monsters, and was inspired by people’s recipes, photos, and family bread history. “There is already such a wealth of expertise here. It is the oldest form of bread making, and it is really wonderful to think about the heritage and legacy of bakers from the past, ”she said.
“Humans already manage microbial populations when they make their sourdough, even if they do not necessarily know what the species’ names are,” she added.
Wolfe and Landis worked with chemists at Tufts to analyze the microbes in the samples. ‘We found that one group of bacteria, the acetic acid bacteria, played an excessive role in shaping the properties of sourdough. It is being studied more in the production of vinegar and kombucha, ”Landis said.
“Thirty percent of the entrees we studied had this group of bacteria, and this entree had significantly different aromas that came off of it, and gradually increased more slowly,” she added. “They found that the age of the appetizer and whether it was purchased from a commercial source tended to influence what microbes were there.”
However, they also found that the microbes in sourdough starters did not differ from place to place – they were the same in Boston as in San Francisco.
‘There are things people do in specific places that affect the crust, flavor and other properties. “It could also be that San Francisco is doing an excellent job of marketing its leaven,” Wolfe said. “Microbes play a big role, but it’s not just about that.”
Why are people willing to put so much effort into a loaf of bread? It’s the same reason Wolfe spent so much time on it. “At the end of the day, people like it,” Wolfe said. “With the current craze, it’s exciting to think about future directions, and where leaven will go from here.”
Landis was honored to play a small role in evolution. “I really love sourdough, and more than that, I love sourdough bakers because they care so much about it,” Landis said. “It really is a privilege to receive something so important to them and to be able to provide more information.”
Go online. Wolfe recommends Andrew Janjigian’s Instagram account, @wordloaf, while Ellis recommends the blog Perfect Loaf. “If people want to get very careful, it has an excellent step-by-step guide,” Ellis said.
Start small. “One thing people do not like about sourdough is that you often use a lot of flour when you keep feeding and throwing it away,” Wolfe said. “I was trying to play with how small I could make an appetizer to reduce the total amount of flour I used.” There is even a hashtag for this type of micro appetizer: #quarantiny.
Measure carefully. If you are making your own appetizer, it is best not to go by the amount of ingredients but by weight. Ellis suggests using a kitchen scale to weigh ingredients.
Turn on your flour. “If your sourdough starter doesn’t work the first time, try another flour,” Wolfe said. “Different flour brands, even the same flour from another company, have different microbes.” Rye flour is minimally processed, which can lead to more and healthier microbes in your sample, Wolfe said.
Maintain multiple beginners. “Over time, you can use one over the other because you prefer the properties of those microbes,” Landis said. “Yes, technique is important, but the biggest thing I learned is that the appetizer you use really matters.”
Customize your process. “There are so many different techniques that people use, such as manipulating the temperature of the appetizer or raising the amount of time to get different rises,” Landis said.
Get creative. Wolfe experimented with adding some unlikely ingredients to his appetizer, such as a tablespoon or two of miso. “Miso is another fermented food with a complex microbial community, which can really enhance the microbial profile of your starter,” Wolfe said. “It ultimately tastes like burnt chocolate or soy sauce and adds a tremendous complexity.”
Record your efforts. “People keep notebooks and log data about their bread,” Landis said. “It reminds me of lab science, especially the way people share their protocols – it’s so specific.”
Branch. If you want to explore the fermented food world further, kombucha is an excellent next step. Ellis said she and her classmates at the Friedman School passed on kombucha scobies or chips of bacteria and yeasts from previous groups that could be used to create new ones. “You combine it with sweet tea, add ginger to make it tastier, and put a coffee filter with a rubber band on top of the pot,” Ellis said. “It does not require much, and it has little maintenance – anyone can do it.”
Monica Jimenez can be reached at [email protected].