Sourdough
Fermentation of gluten free flours while making sourdough bread
breaks down some of the gluten cross-contamination in "gluten-free" flour
Click here to see a study of cross contamination in "gluten-free" grains and flours. In this small study, it appears that flour is more likely to be contaminated than is the whole grain, so that rinsing, drying, and milling your own flour is probably the safest choice.
This Discover Magazine article, The Biology of Sourdough, is a good article to give you some background about how sourdough works. In addition, this article, which explains the development of a "from scratch" starter, is also very informative.
There seems to be some confusion in various recipes I have seen online as they call for only yeast to make a sourdough. Yeast alone is not sourdough starter, and the commercial breadmaking yeast in stores is not the same type of yeast that is in sourdough! Lactic acid bacteria actually produces the acidic "sour" flavor in sourdough, and it is also lactic acid bacteria (not yeast) that causes the breaddown of the gluten protein. The efficiency of this breakdown depends on the strain of lactobacillus, so it cannot be guaranteed, but fermentation is thought to help with reducing cross-contamination in gluten-free flour.
To create a soudough starter you have three options:
- Create one completely from scratch with just flour and water
- Create one completely from scratch containing just flour, water, and an acidic ingredient (to discourage the bad bacteria)
- Add a "booster" at the beginning. A booster is a bit of starter from another source, such as a commercial dried starter or water kefir. It contains the right kind of bacteria and yeast so they are definitely there from the beginning and just need to be increased.
Here is a recipe for a Gluten-Free Sourdough Starter which uses an optional booster.
Once you have an established starter, you can keep it going by continuing to feed it, or you can dry some of it to preserve it for when you need it. See Drying Sourdough Starter for Long-Term Storage (how to store your starter so you don't have to buy it again)
If you would prefer to know for sure what is growing in the starter rather than just "seeing what happens" when you try to make it from scratch, here are some gluten-free boosters you can buy and some ideas for using them:
- Florapan French Sourdough Starter
This is a dried gluten-free starter sold by King Arthur. Per King Arthur, it contains lactobacillus brevis, yeast (unlisted type), lactose, soy, and beef traces. One research study using Florapan referred to it as Lactobacillus brevis L62 (Florapan L62, Lallemand SA, Blagnac Cedex, France). Lactobacillus brevis also creates water kefir grains (Wikipedia). - Cultures for Health GF Brown Rice Sourdough Starter
- Sourdough Starter Cultures from Sharon Kane's Gluten Free Sourdough website
- Water Kefir Grains to make water kefir which can be used as a booster
Sharon Kane uses water kefir as a booster extensively in her book The Art of Gluten Free Sourdough Baking. Here is her website: Gluten Free Sourdough. And here is more about the Composition of Water Kefir Grains: Bacteria and Yeast
Here are directions for building up the amount of starter when you are using a booster: Gluten-Free Sourdough Starter: a four day culture shock
To make sourdough bread, the sourdough starter is used as a leavening agent. Some of the starter is added to fresh, unfermented flour which is then allowed to rise for varying amounts of time, usually a matter of a few hours. During the rising time, some of the residual gluten cross contamination in the flour would be broken down, but it would probably not be long enough to be complete, or close to complete. Full degradation of gluten requires long fermentations with a combination of several strains of different lactic acid bacteria and/or with the addition of a suitable peptidase. (See Sourdough Fermentation of Wheat Flour does not Prevent the Interaction of Transglutaminase 2 with α2-Gliadin or Gluten)
These links refer to wheat sourdoughs, but are interesting discussions:
Cultures for Health Sourdough ebook
Art of Gluten-Free Baking: Sourdough starter, gluten-free
Gluten-Free Sourdough Flatbread recipe
Gluten Free Sourdough Bread, recipe from Baking Magique blog
See Urchina's simplified injera recipe in the comments
Ethiopean Injera, by Korena in the Kitchen
Injera, by breadchick
Injera (fermented teff flatbread)
More about injera
Basic Gluten-Free Sourdough bread recipe
What is Sourdough?
Aspergillus niger enzyme
The Gluten-Free Diet: Testing Alternative Cereals Tolerated by Celiac Patients (search sourdough)
The following are some wheat-based sourdough starters (I may try converting one to gluten-free, but this would take many, many divisions and feedings to be sure it is safe):
Carl Griffith's 1847 Oregon Trail Sourdough Starter
Sourdo.com
King Arthur
Hydration of the starter goes by weight. If the weight of water is equal to the weight of flour your hydration is 100%. The weight of water divided by the weight of flour gets you the percentage. So, 8 ounces of water with 5 ounces of flour is 160% hydration (8/5=1.6). Higher hydration favors development of the lactic acid bacteria vs yeast. See Debra Wink's post, liquid vs firm sourdough.
From https://www.kingarthurflour.com/professional/yeast.html
There is an interesting relationship in what we call San Francisco Sourdough between the wild yeast, Candida milleri, and the dominant lactobacillus strain, Lactobacillus sanfranciscensis. C. milleri cannot utilize maltose during fermentation, while L. sanfranciscensis is happy to use it. And once it does, it excretes glucose. This is fortunate for C. milleri, because it is fond of glucose, and ferments this simple sugar readily. At the same time, competing bacterial species are inhibited by the presence of so much glucose, and this is to the benefit of L. sanfranciscensis, whose development is therefore favored. A last factor in this relationship pertains to acidity. L. sanfranciscensis produces a lot of acetic acid, which contributes significantly to the flavor we associate with sourdough bread. C. milleri is more tolerant of an acidic environment than many yeast varieties. The high level of acidity prevents competing yeasts from dominating the culture, much to the benefit of C. Milleri.
There is an interesting relationship in what we call San Francisco Sourdough between the wild yeast, Candida milleri, and the dominant lactobacillus strain, Lactobacillus sanfranciscensis. C. milleri cannot utilize maltose during fermentation, while L. sanfranciscensis is happy to use it. And once it does, it excretes glucose. This is fortunate for C. milleri, because it is fond of glucose, and ferments this simple sugar readily. At the same time, competing bacterial species are inhibited by the presence of so much glucose, and this is to the benefit of L. sanfranciscensis, whose development is therefore favored. A last factor in this relationship pertains to acidity. L. sanfranciscensis produces a lot of acetic acid, which contributes significantly to the flavor we associate with sourdough bread. C. milleri is more tolerant of an acidic environment than many yeast varieties. The high level of acidity prevents competing yeasts from dominating the culture, much to the benefit of C. Milleri.
References
Sourdough fermentation may enhance the recovery from intestinal inflammation of coeliac patients at the early stage of the gluten-free diet.
2017: Selected Probiotic Lactobacilli Have the Capacity To Hydrolyze Gluten Peptides during Simulated Gastrointestinal Digestion
2016: Screening sourdough samples for gliadin-degrading activity revealed Lactobacillus casei strains able to individually metabolize the coeliac-disease-related 33-mer peptide Twenty gliadin-degrading LAB strains were isolated from 10 sourdoughs made in different ways and from different geographical regions. Fifteen of the 20 isolated strains were identified as Lactobacillus casei, a species usually reported as subdominant in sourdough populations. The other 5 gliadin-degrading strains belonged to the more commonly encountered sourdough species Leuconostoc mesenteroides and Lactobacillus plantarum. A copy of the paper is at the bottom of this page. The best L. Casei strain was from a rye sourdough starter from a bakery in Poznan,Poland. Here is some Polish Pumpernickel (Rye) Sourdough Starter.
Recipe for fermented coconut water
2016: Sourdough-Based Biotechnologies for the Production of Gluten-Free Foods and on the same topic, 2014: Gluten-Free Wheat? Q&A Details Intriguing Research and Giusto, the Italian company that has brought this to market.
2015: Sourdough Fermentation of Wheat Flour does not Prevent the Interaction of Transglutaminase 2 with α2-Gliadin or Gluten
2014: Testing safety of germinated rye sourdough in a celiac disease model based on the adoptive transfer of prolamin-primed memory T cells into lymphopenic mice (Used Florapan sourdough starter)
2006: VSL#3 probiotic preparation has the capacity to hydrolyze gliadin polypeptides responsible for Celiac Sprue
2012: A combination of two lactic acid bacteria improves the hydrolysis of gliadin during wheat dough fermentation.
2004: Sourdough Bread Made from Wheat and Nontoxic Flours and Started with Selected Lactobacilli Is Tolerated in Celiac Sprue Patients Lactobacillus alimentarius15M, L. brevis 14G, L. sanfranciscensis 7A, and L. hilgardii 51B were selected previously on the basis of their ability to hydrolyze gliadin fractions of wheat sourdoughs (18)
Functionality of lactic acid bacteria peptidase activities in the hydrolysis of gliadin-like fragments.
Sourdough entry on Wikipedia
Gluten breakdown by lactobacilli and pediococci strains isolated from sourdough
Gluten hydrolysis and depolymerization during sourdough fermentation.
Comparison of sourdoughs with acid control doughs demonstrated that glutenin hydrolysis and gluten depolymerization in sourdough were mainly caused by pH-dependent activation of cereal enzymes
* 2008: Use of selected sourdough strains of Lactobacillus for removing gluten and enhancing the nutritional properties of gluten-free bread.
2002: Proteolysis by Sourdough Lactic Acid Bacteria: Effects on Wheat Flour Protein Fractions and Gliadin Peptides Involved in Human Cereal Intolerance
L. brevis 14G hydrolyzed 39 polypeptides, 24 of which were albumins and globulins. Compared to that of L. alimentarius 15M, the hydrolysis was more pronounced, since all of the albumin and globulin polypeptides and 12 of the 15 gliadins were degraded by hydrolysis factors of ≥50%. L. sanfranciscensis 7A showed proteolysis towards the largest number (41) of polypeptides, 24 albumins and globulins and 18 gliadins.
Biodiversity of lactic acid bacteria and yeasts in spontaneously-fermented buckwheat and teff sourdoughs
This study found that Lactobacillus plantarum (which produces mostly lactic rather than acetic acid) dominated in all naturally fermented buckwheat sourdoughs
2016: Characterization of the Bread Made with Durum Wheat Semolina Rendered Gluten Free by Sourdough Biotechnology in Comparison with Commercial Gluten-Free Products. (used not just sourdough fermentation, but also fungal proteases).
2004: Gluten Hydrolysis and Depolymerization during Sourdough Fermentation
2007: Highly Efficient Gluten Degradation by Lactobacilli and Fungal Proteases during Food Processing: New Perspectives for Celiac Disease
2002: Proteolysis by sourdough lactic acid bacteria: effects on wheat flour protein fractions and gliadin peptides involved in human cereal intolerance.
Mechanism of Degradation of Immunogenic Gluten Epitopes from Triticum turgidum L. var. durum by Sourdough Lactobacilli and Fungal Proteases
Lactic Acid Fermentation in Sourdough
2004: Sourdough bread made from wheat and nontoxic flours and started with selected lactobacilli is tolerated in celiac sprue patients
Probiotic-Derived Polyphosphate Enhances the Epithelial Barrier Function and Maintains Intestinal Homeostasis through Integrin–p38 MAPK Pathway
Survey on the nutritional and health aspects of teff
(with details of microbiota/fermentation)
Steps in Enjera production
Update in bread fermentation by lactic acid bacteria
Testing safety of germinated rye sourdough in a celiac disease model based on the adoptive transfer of prolamin-primed memory T cells into lymphopenic mice.One result of this study is that current antibody-based prolamin detection methods may fail to detect antigenic gluten fragments in processed cereal food products.
2017: Selected Probiotic Lactobacilli Have the Capacity To Hydrolyze Gluten Peptides during Simulated Gastrointestinal Digestion
2016: Screening sourdough samples for gliadin-degrading activity revealed Lactobacillus casei strains able to individually metabolize the coeliac-disease-related 33-mer peptide Twenty gliadin-degrading LAB strains were isolated from 10 sourdoughs made in different ways and from different geographical regions. Fifteen of the 20 isolated strains were identified as Lactobacillus casei, a species usually reported as subdominant in sourdough populations. The other 5 gliadin-degrading strains belonged to the more commonly encountered sourdough species Leuconostoc mesenteroides and Lactobacillus plantarum. A copy of the paper is at the bottom of this page. The best L. Casei strain was from a rye sourdough starter from a bakery in Poznan,Poland. Here is some Polish Pumpernickel (Rye) Sourdough Starter.
Recipe for fermented coconut water
2016: Sourdough-Based Biotechnologies for the Production of Gluten-Free Foods and on the same topic, 2014: Gluten-Free Wheat? Q&A Details Intriguing Research and Giusto, the Italian company that has brought this to market.
2015: Sourdough Fermentation of Wheat Flour does not Prevent the Interaction of Transglutaminase 2 with α2-Gliadin or Gluten
2014: Testing safety of germinated rye sourdough in a celiac disease model based on the adoptive transfer of prolamin-primed memory T cells into lymphopenic mice (Used Florapan sourdough starter)
2006: VSL#3 probiotic preparation has the capacity to hydrolyze gliadin polypeptides responsible for Celiac Sprue
2012: A combination of two lactic acid bacteria improves the hydrolysis of gliadin during wheat dough fermentation.
2004: Sourdough Bread Made from Wheat and Nontoxic Flours and Started with Selected Lactobacilli Is Tolerated in Celiac Sprue Patients Lactobacillus alimentarius15M, L. brevis 14G, L. sanfranciscensis 7A, and L. hilgardii 51B were selected previously on the basis of their ability to hydrolyze gliadin fractions of wheat sourdoughs (18)
Functionality of lactic acid bacteria peptidase activities in the hydrolysis of gliadin-like fragments.
Sourdough entry on Wikipedia
Gluten breakdown by lactobacilli and pediococci strains isolated from sourdough
Gluten hydrolysis and depolymerization during sourdough fermentation.
Comparison of sourdoughs with acid control doughs demonstrated that glutenin hydrolysis and gluten depolymerization in sourdough were mainly caused by pH-dependent activation of cereal enzymes
* 2008: Use of selected sourdough strains of Lactobacillus for removing gluten and enhancing the nutritional properties of gluten-free bread.
2002: Proteolysis by Sourdough Lactic Acid Bacteria: Effects on Wheat Flour Protein Fractions and Gliadin Peptides Involved in Human Cereal Intolerance
L. brevis 14G hydrolyzed 39 polypeptides, 24 of which were albumins and globulins. Compared to that of L. alimentarius 15M, the hydrolysis was more pronounced, since all of the albumin and globulin polypeptides and 12 of the 15 gliadins were degraded by hydrolysis factors of ≥50%. L. sanfranciscensis 7A showed proteolysis towards the largest number (41) of polypeptides, 24 albumins and globulins and 18 gliadins.
Biodiversity of lactic acid bacteria and yeasts in spontaneously-fermented buckwheat and teff sourdoughs
This study found that Lactobacillus plantarum (which produces mostly lactic rather than acetic acid) dominated in all naturally fermented buckwheat sourdoughs
2016: Characterization of the Bread Made with Durum Wheat Semolina Rendered Gluten Free by Sourdough Biotechnology in Comparison with Commercial Gluten-Free Products. (used not just sourdough fermentation, but also fungal proteases).
2004: Gluten Hydrolysis and Depolymerization during Sourdough Fermentation
2007: Highly Efficient Gluten Degradation by Lactobacilli and Fungal Proteases during Food Processing: New Perspectives for Celiac Disease
2002: Proteolysis by sourdough lactic acid bacteria: effects on wheat flour protein fractions and gliadin peptides involved in human cereal intolerance.
Mechanism of Degradation of Immunogenic Gluten Epitopes from Triticum turgidum L. var. durum by Sourdough Lactobacilli and Fungal Proteases
Lactic Acid Fermentation in Sourdough
2004: Sourdough bread made from wheat and nontoxic flours and started with selected lactobacilli is tolerated in celiac sprue patients
Probiotic-Derived Polyphosphate Enhances the Epithelial Barrier Function and Maintains Intestinal Homeostasis through Integrin–p38 MAPK Pathway
Survey on the nutritional and health aspects of teff
(with details of microbiota/fermentation)
Steps in Enjera production
Update in bread fermentation by lactic acid bacteria
Testing safety of germinated rye sourdough in a celiac disease model based on the adoptive transfer of prolamin-primed memory T cells into lymphopenic mice.One result of this study is that current antibody-based prolamin detection methods may fail to detect antigenic gluten fragments in processed cereal food products.