Years ago as the Levies were learning about sourdough bread-making from a neighbor, he explained how when he was exhibiting bread-making at a city fair, a health inspector dropped by. He was checking all the booths, vendors and exhibits to make sure they were handling food safely.
The inspector was alarmed when he saw that unbaked sourdough bread was sitting in the heat uncovered. But the neighbor explained that it was a sourdough bread made with starter, to which the inspector said, “Well then that is a whole other matter,” and walked away.
Surely story of this bread sitting in the outdoors must make us all ask what that inspector knew that we might not?
We know that sourdough starter contains billions of bacteria. We also know that it features varieties of Lactobacilli(LAB) that work with wild yeast in a symbiotic relationship to improve crumb and flavor in bread making. The symbiotic process the LAB and yeast produce other favorable outcomes.
Wild Yeast and Bacteria in Sourdough Bread
A research team at the University of Zagreb in Croatia undertook a study to identify lactic acid bacteria (LAB) that occurs naturally in sourdough in hopes of using them to improve bread quality and prolonging the shelf life of various bread types. Though different species, they studied Lactobacillus reuteri as the dominant lactic acid bacteria in their sample sourdough obtained from Dr. Jūratė Repečkienė of the Institute of Botany, Nature Research Centre, Vilnius, Lithuania.
However, as you move around the world the yeast strains and bacteria vary some:
|Common yeast in sourdough starter:||Common bacterial strains in starter:|
|• Saccharomyces diarensis||• Lactobacillus brevis|
|• Saccharomyces exiguus||• Lactobacillus plantarum|
|• Candid milleri||• Lactobacillus sanfranciscensis|
This specific LAB (bacteria) strain, just like the ones listed above, produced antimicrobial substances that had a significant “antimould activity on the bread surfaces during 12–15 days of storage. The use of antimicrobial active sourdough could prevent bread defects such as ropiness or molding… Thus, the strains producing antimicrobial substances can be used as bio-preservatives, extending the shelf life and enhancing food safety” 1
Sourdough Bread is Mold Resistant
LAB (bacteria) also converts the linoleic acids in wheat flour into a compound with powerful antifungal properties. In a study at the University of Alberta, Edmonton, Canada, Michael Gaenzle and his colleagues showed that the extra fermentation in real sourdough bread making releases two antifungal compounds. His team found, that because “preservatives can be eliminated from the recipes, and because sourdough bread has a more distinct and richer flavor compared to bread produced with yeast only” it may offer other applications in retarding fungal growth in other foods.
They also found that while these two antifungal compounds “and their formation by cereal or microbial enzymes had been described previously, but their antifungal activity and their generation in food production was unknown… [we are] a step towards understanding how and why lactobacilli metabolize fatty acids. This could be useful in the long term to improve our understanding of the biology of these organisms.”2
Their conclusion, among many other similar studies, showed that sourdough starter creates an acidic environment that other bacteria do not tolerate. The acid produced is lactic acid and is a byproduct of fermentation in the starter. This acidic environment prevents unwanted yeast and bacterial colonization, which in turn helps to keep bread made this way fresh longer.
LAB After Baking
Okay, so we know that sourdough starter is full of “good” bacteria, but can that bacteria survive the heat of baking, if not what good is it after the fact?
There is some evidence that shows even after baking, the LAB may be beneficial in our gut as a prebiotic and probiotic source. Consuming both regularly my help to improve gut health, by easing digestion.3
In the few last decades, molecular-based investigations have “confirmed the species diversity and metabolic complexity of the human gut microbiota.” These microbes play a crucial role in our health, both “in protection against disease and maintenance of gut function.” More recently we have learned about the beneficial gut microbiota, but “it is generally accepted that bifidobacteria and lactobacilli are [the] important components of what might be termed the beneficial gut microbiota.”4 This means the very same bacteria that helps bread rise, is common in our gut. So even though it might not survive baking heat, there it is in our gut anyway.
Michelle recently posted how that might be taking place as she described “The Great Starter Experiment.” Bakers were selected worldwide and given identical flour and sourdough starts. But after eighteen months, loaves they were baking were not identical. According to writer Veronique Greenwood, who writes for the BBC explained that almost “all the microbes found in the starters themselves were …found on the bakers’ hands [and are] what’s making bread rise.” Clearly, as bakers what we make gets into our guts.
This study also points to the fact that the original cultures could not survive local bacterial and wild yeast invasions from the baker’s home environments. Nor could most bacteria survive the cultures used in sourdough. Thus our inspector was not concerned about bread sitting outdoors.
In the past few years since that first inspection, Abigail and her family have had inspections at various outdoor fairs and farmer’s markets, all with the same result. Here is a fun video clip from the Orem Colonial Feast:
Though the text number and announcement are expired, you can stop by the bakery at 421 S 200 E, Spanish Fork, UT on Tuesday or Friday 9AM–6PM and Saturday from 10AM–4PM and try a sample. We would love to see you.
One study shows that sourdough can improve the nutritional quality of bread from “acid production, suggested to retard starch digestibility and to adjust pH to a range which favors the action of certain endogenous enzymes, thus changing the bioavailability pattern of minerals and phytochemicals. This is especially beneficial in products rich in bran to deliver minerals and potentially protective compounds in the blood circulation.”5
Sourdough bread has been shown to have resistant starch levels that are higher than bread baked with commercial yeast.6 “Resistant starch is a carbohydrate that resists digestion in the small intestine and ferments in the large intestine. As the fibers ferment they act as a prebiotic and feed the good bacteria in the gut.”7
“The increase in resistant starch is also thought to be due to the presence of lactic acid” and “we may conclude that sourdough fermentation is a technique able to reduce the glycemic response to bread…”8 Knowing this and everything else in this post, don’t you think it is time to buy some bread.
1 Jonkuvienė, Vaičiulytė-Funk, Šalomskienė, Alenčikienė, and Mieželienė, “Potential of Lactobacillus reuteri from Spontaneous
Sourdough as a Starter Additive for Improving Quality Parameters of Bread,” Food Technol Biotechnol, SEP 2016
2 American Society for Microbiology. “Why sourdough bread resists mold” ScienceDaily, 21 February 2013
2 Tuohy, Probert, Smejkal, and Gibson, “Using probiotics and prebiotics to improve gut health,” Drug Discov Today, AUG 2003
4 Poutanen , Flander, Katina, “Sourdough and cereal fermentation in a nutritional perspective,” Food Microbiol, OCT 2009
5 Tuohy, Probert, Smejkal, and Gibson, ibid.
6 Scazzina,”Sourdough bread: Starch digestibility and postprandial glycemic response,” Journal of Cereal Science, May 2009
7 What is Resistant Starch?“, The John Hopkins Patient Guide to Diabetes.
Author: Darryl Alder, retired Scouter and outdoorsman, who spent too many hours over a campfire using a dutch oven, and loves sharing recipes for the kitchen and the campfire. You can read many of his outdoor recipes here.