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Why Extended Sourdough Fermentation?

Cereals, Pseudocereals, Legumes tend to store nutritious substances they produce as compacted complex molecules within their seeds.  When this seeds contact with sufficient water, the enzymes in seed germ start to activate. This enzyme activation breaks complex molecules (proteins, fats/oils, starches, celluloses) into simple molecules (amino acids, fatty acids, maltose, glucose etc.) that can be used by the seed to sprout. Human body also needs to simplify seed’s complex molecules to be able to metabolize. In order to do that, our bodies release several enzymes through mouth to gut. However, these enzymes that our bodies released are not enough for complete metabolization of nutrients we eat. Beneficial microorganisms wthin our guts help us in this metabolization process. Unfortunately, bad nutrition habits damage these beneficial microorganisms and healthy metabolization process of nutrients. So, the complex molecules that can not be metabolized sufficiently due to damaged intestinal microbiota or any kind of malfunction of digestion will eventually be toxic to our bodies. 

Sourdough involves Yeasts and Lactic Acid Bacteria (LAB) that directly come from flour chosen used to make sourdough. The microbiota that lives on seed flour is special for its cereal species. The microbiota will eventually prevail on sourdough made from that specific cereal. Microorganisms that constitute the microbiota are best adapted on that species (especially on metabolization of nutrients of the species). This high adaptation on metabolization of nutrients means specialized on converting complex molecules of that certain cereal species into simplified ones to be used for consumption by microorganisms. This adaptation is also beneficial for sourdough fermentation of the cereal. The microorganisms act like intestinal microbiota and help releasing bioactive compounds (from the cereal) that can be metabolized easily by our bodies.

A bioactive compound is simply defined as a substance that has a biological activity related to its ability to modulate one or more metabolic processes, which results in the promotion of better health conditions. Best way to increase maximum availability of bioactive compounds within sourdough is to extend fermentation time as much as possible. In order to extend time successfully, fermentation of sourdough should take place in fridge at around 6-10 Celsius degree to prevent overfermantation and deterioration. During long fermentation process first yeast cells and aerobic bacteria grows rapidly and consume most of oxygen, then anaerobic bacteria starts to grow and most of the beneficial bioactive compounds are produced during last part of fermentation cycle. So, as duration increases, availability (variety & amount) of nutritious bioactive compounds increases. This gives our bodies opportunities of less job on digesting process and removal of toxic residues.

This gives our bodies opportunities of less job on digesting process and removal of toxic residues.

However, commercial yeasts include just a single yeast species and this singularity just gives dough to leaven by producing carbon dioxide within a short time. This singularity and short fermentation time do not provide enough degradation of complex molecules into simplified ones. So, the digestion process prolongs, limited bioactive compounds are metabolized and extra job is done by our bodies to detoxify harmful substances. Especially people who have digestion sensitivity will probably suffer from inconvenience created by short fermentation including commercial yeast.  

As a result, long cold fermented sourdough made especially from high fibre foods is much better for appropriate nutrition. This appropriateness includes mainly three points. First is the increased amount and variety of bioactive compounds released by action of sourdough culture. Second is rich aromatic and flavor compunds. Third is reduction of toxic effect of several substances by microbial action. This detoxification also includes partial removal of toxic effect of wheat flour gluten and potential gluten contamination of gluten free flours.

Sources

Kati Katina and Kaisa Poutanen (2013), Chapter 9: Nutritional Aspects of Cereal Fermentation with Lactic Acid Bacteria and Yeast ; Elke K. Arendt and Alice V. Moroni (2013), Chapter 10: Sourdough and Gluten-Free Products. In: Marco Gobbetti, Michael Gänzle (eds) Handbook on Sourdough Biotechnology. Springer Science+Business Media New York

Di Cagno R, De Angelis M, Auricchio S, Greco L, Clarke C, De Vincenzi M, Giovannini C, D’Archivio M, Landolfo F, Parrilli G, Minervini F, Arendt E, Gobbetti M (2004) Sourdough bread made from wheat and nontoxic flours and started with selected lactobacilli is tolerated in celiac sprue patients. Appl Environ Microbiol 70:1088–1096.

De Angelis M, Coda R, Silano M, Minervini F, Rizzello CG, Di Cagno R, Vicentini O, De Vincenzi M, Gobbetti M (2006) Fermentation by selected sourdough lactic acid bacteria to decrease coeliac intolerance to rye flour. J Cereal Sci 43:301–314.

Rizzello CG, De Angelis M, Di Cagno R, Camarca A, Silano M, Losito I, De Vincenzi M, De Bari MD, Palmisano F, Maurano F, Gianfrani C, Gobbetti M (2007) Highly efficient gluten degradation by lactobacilli and fungal proteases during food processing: new perspectives for celiac disease. Appl Environ Microbiol 73:4499–4507

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