Introduction: Sourdough

About: Polymath and idiot. Mostly idiot.

In some of my bread instructables there were many comments about people not having access or not being able to start a sourdough. Also I have seen many awkward explanations with wrong terms and misconceptions. I want to use this instructable to show everyone how to start a sourdough, how to maintain it, what is happening inside of it and what to do with it. First I made an experiment with different flour types to show how fast and easy it is to obtain one. After that I wrote down some excerpts about the history, the microorganisms, the metabolism and the maintaining of sourdoughs. Later there are instructions to have always access to yeast and sourdough at home and make tasty food with it.

  • Flour types
  • Experiment I
  • Experiment II
  • History of Sourdough
  • Microorganisms in a Sourdough
  • What to do with the Discard?
  • Nutritional Value
  • Comparison with Yeast
  • Preservation of Sourdough
  • Adapting a Sourdough
  • Malting for Fodder
  • Lievito Madre
  • Hermann the German
  • Get it online
  • Glossary
  • Step 1: What Is Sourdough?

    A sourdough is a fermenting mixture of flour with water. Either it was merged with a starter sponge from a previous dough or it contracted ubiquitous spores from wild lactobacilli and yeast already present in the flour. The microorganisms feast on the nutritions within the flour, proliferate and produce alcohol, acids and CO2. This way the sourdough acts as a natural leavening for baking products while also improving the taste and aroma. Some flours even need to be fermented with a sourdough to make it possible to be used in pastries. Starter sponge is the first step in a sourdough recipe and is further mixed with water and flour to a natural leaven. Temperature and water/flour ratio of further steps influence the growth (pictured) or metabolism of the microorganism and therefor the result of the baking procedure. Up to 5 steps can be used to maximise aroma, taste and baking capability. Later I will explain more benefits of using sourdough, but first I want to show you in the following experiment how different flours influence the pace to obtain one.

    Step 2: Flours Used

    Flours differ not just in the grain they were made of, but also in the coarseness and the ratio of grain components. This affects the content of proteins, minerals, fibers and starch. Flours with the lowest coarseness have the highest starch content while flours with the highest coarseness have the highest fiber, minerals, vitamins and protein content (absolute). Now fibers and starch are both made of polysaccharides, but not every microorganism is able to process every sugar molecule. The yeast that we use mainly for brewing beer and also baking bread, Saccharomyces cerevisiae, can metabolise glucose, fructose, mannose, galactose, saccharose, maltose, maltotriose and raffinose, which we find mainly in the endosperm of fruits. It cannot metabolise pentoses like ribose, xylose, arabinose or cellobiose, lactose, inulin and cellulose which are fiber. But other yeasts or lactic acid bacteria can use them. The following experiment is going to show the ability to grow a sourdough and the development in 8 different flour types from low mineral content to full for 3 types of grain.

    • wheat flour: 450, 550, 1050 , full wheat
    • spelt: 630, 1050
    • rye: 1150, full rye

    The following spreadsheet shows the different international names for similar flour types.

    pastry floursoft flour40500
    all-purpose flourplain flour5500
    first clear flourvery strong or hard10502
    white whole wheatwholemeal1700Farina integrale di grano tenero

    The German flour types are defined by the amount of ash (minerals) in milligrams that are left if you burn 100 grams of the flour in a muffle furnace at high temperatures. The higher the amount the bigger the variety of ingredients.

    Step 3: Tools Used

    An old apothercary scale is used to score the exact weight of 5 grams. My decorated spoon from childhood helps to measure the exact same amount of water and fill it into the small glass containers. Wooden toothpicks are used to stir the flours with the water to avoid cross contamination. And 8 little jam jars help to contain the experiments for the sourdough starters. Test-tubes seemed to be unusable for this experiment since stirring the dough and the production of gas could lead to imbalanced developments of the dough mass. The wide jars seem better appropriate for stirring and the release of gas, as long as I opened the lids every 12 hours to let the gas escape. With 5 grams of sugar the yeast can produce 1.45 liters of CO2 gas in a 0.045 liter container.

    Step 4: Day 0, Evening

    All glass jars are labelled, then get 5 grams of a certain flour and 5 grams of water, and are stirred with a toothpick. The following days they will be stirred every morning and evening, pictures of the results are provided in the following steps. There are 3 indicators for a successful sourdough, the smell, the consistency and the presence of bubbles.

    The smell is a subjective indicator because our nose scans for edible food and gives us warning signals for non-edible food. The gases released by microorganisms inform us about the freshness of our food and therefor fermented food comes with a bad smell until we tried it and our body understands the benefits. Now the last part sounds a bit esoteric, but if you ever make your own Kombucha, smell it, drink it and then smell it again, you will know what I mean. Our brain can calibrate the perception of smell and thus I reduced the range to:

    -, slightly, sour, very sour, foul.

    The consistency indicates the hydration of the flour into a gluten matrix (glutenin + gliadin). The stronger the matrix of long protein chains, the stronger the viscosity of the flour + water mixture. If the microorganisms start eating the gluten then water will leave the agglomeration and the mixture becomes fluidly again. Of course the water needs to dissolve first in the flour and might look like a crumbly mother dough. The range we are differencing is:

    -, crumbly, mother dough, gummy, foamy, wet, watery

    The microorganisms produce CO2 which simply gets stuck between the network of long protein chains. The more activity, the bigger the bubbles. If the size of the bubbles decreases the microorganisms are running out of food. The range we are differencing is:

    -, tiny, small, medium, big

    Step 5: Day 1, Morning

    GrainFlour TypeBubble SizeConsistenceSmell
    550-mother dough-

    Step 6: Day 1, Evening

    GrainFlour TypeBubble SizeConsistenceSmell
    550smallmother doughslightly
    full-mother doughslightly

    Step 7: Day 2, Morning

    GrainFlour TypeBubble SizeConsistenceSmell
    fullmanyfoamyvery sour
    fullsmallmother doughsour

    Step 8: Day 2, Evening

    GrainFlour TypeBubble SizeConsistenceSmell

    Step 9: Day 3, Morning

    GrainFlour TypeBubble SizeConsistenceSmell

    Step 10: Day 3, Evening

    GrainFlour TypeBubble SizeConsistenceSmell

    Step 11: Day 4, Morning

    GrainFlour TypeBubble SizeConsistenceSmell
    Spelt630smallfoamybubble gum

    There is another indicator for a successful sourdough, look at the even distribution of condensed water drops in the lid.

    Step 12: Day 4, Evening (Final Results)

    GrainFlour TypeBubble SizeConsistenceSmell
    Wheat405tinywetlight sour
    550biggummylight sour
    Rye1150tinywetlight sour

    Step 13: Analysis:

    The 8 sourdough starters were mixed at a ratio of 1:1 water to flour. This ratio wasn't suitable for all flour types because one was too dry for the microorganisms to develop a sustainable environment that could keep out mould and one was too watery to keep trapped air. Simpler flour types helped the microorganisms proliferate faster than flour types with a higher coarseness, but the latter provided nutrition for a longer time. When the microorganisms had consumed most of the nutrimental saccharoses and proteins then water would debond and be set free again. Therefor it is obvious that a sourdough tolerates minor differences in the ratios of water and flour as it was possible to revive watery test objects by stirring, effectively spreading unprocessed food. The sour smell is always prevalent, independent from the consistency. If a recipe asks for a sourdough with a resulting consistency like crumbly or foamy, then the sourdough with its trapped bubbles would be used as a leavening. If the recipe asks for a wet or mushy sourdough, then it is just to provide acidity, aroma and flavour.

    Step 14:

    Other starchy flours should also be able to develop into a sourdough. Therefor I grinded rice, chickpeas, lentils, quinoa, chia and amaranth into a flour. I also had green pea flour and used professional pizza flour as a control medium.

    I do not expect the chia flour to create a successful sourdough because the shell of the seed has a property to bind water into a slime. A ratio of 1:1 is not going to work because chia can bind 50 times the amount of water of its own weight. But let's have a look at the secound experiment now.

    Step 15: Day 0

    The following pictures are always in this order: rice, chickpeas, lentils, peas, quinoa, chia, amaranth, pizza flour. All jars contain 5 grams flour and 5 grams water. This time I did not stir the starters after their first mixing.

    Step 16: Day 1

    Flour TypeBubble SizeConsistenceSmell

    Step 17: Day 2

    Flour TypeBubble SizeConsistenceSmell
    rice-mother doughmouthwash
    chickpeastinymother doughsour
    amaranth-mother dough-

    Step 18: Day 3 (Final Results)

    Flour TypeBubble SizeConsistenceSmell

    Step 19: Analysis

    Very surprised about the smells of the different sourdoughs, rice smells like mouthwash, quinoa smells like bacon and chickpeas smell like beans. This could be used to increase the aroma in a sourdough bread, especially a bread that tastes like bacon but with vegetarian ingredients. The flours all developed as expected and I consider the experiement a success. The flour from lentils was very fast in developing a sour and fruitful. The chia seeds bind water and contain too much oil to prevent the lactobacillales from building a sourdough acidic environment. In the experiments we can determine the current growth phase by the production of C02 resulting in bubbles of different sizes.

    I merged all sponges with my starter sponge and now have 14 different flour types in it.

    Step 20: The History of Sourdough

    The oldest proof for the usage of a sourdough was found in Switzerland and dates back to 3700BC. There are also some older archaeological finds from ancient Egypt, but it cannot be determined if the goddess Isis gave the people sourdough or just grain porridge.

    The first text that mentions sourdough? Well the nonpresence is mentioned several times in the 2nd book of Mose chapter 12, when the people had to eat unleavened bread. Which has led to the prohibition of any ferment during passover for religious people. Which is alright because another god gave sourdough to us, the woodwose Rübezahl. Pliny the Elder wrote about sourdough in his Natural history (naturae historiarum) in the year 77AC. Around this time the apostles Luke and Matthew wrote down the parable of the leaven. In the Middle Age sourdough was also used to turn skins into soft leather. In the Age of Enlightenment mainly chemists were studying the phenomenon of fermentation. This changed in the beginning of the 19th century when Rudolf Virchow found bacteria in a ferment and contributed to cell theory. Then Robert Remark discovered cell division which is a very important step for the understanding of sourdough. The discovery of yeast and its scientific name was given by Theodor Schwann; "Zuckerpilz" (Saccharose= sugar, Myces= fungus) in the 1830s. Just 30 years later Louis Pasteur found the airborne nature of germs. The consequential industrial production of yeast enabled bakeries to produce bigger and more loafs, while sourdough became an unwanted necessity for rye flour and alike. Only people who lived in rural areas preferred the taste and nutritional value of sourdough. Actually during the Klondike Gold Rush sourdough was so treasured for the miners, they kept it close to their body in the cold conditions to keep it alive. Then the world wars raised the demand for different food processing.

    (In the picture you can see wild wheat growing out of a pavement in Germany. It is food so we don't treat it like a pest.)

    Step 21: The Development of Sourdoughs

    The first sourdoughs were simple mixes of water and flour. A part of the dough was stored for the next day and merged with the new one. After scientists developed an understanding of the microorganisms and their preferred environments, the complexity of sourdoughs increased. The single step of just letting the mixture rest and then making a flatbread was not satisfactory.

    The three-stage sourdough

    improves the development of all useful microorganisms (BP = baker`s percentage):

    1. (yeast proliferation) BP 200-220 for 5 to 8 hours at 25-26°C.
    2. (acid and aroma) BP 150-170 for 6 to 10 hours at 23-28°C.
    3. (leavening) BP 180-200 for 3 to 10 hours at 25-32°C.

    This time schedule allows to prepare a bread within 24 hours, but could conflict with the daily schedule and allows no promptly adaption to demand.

    Berliner Kurzsauer

    was developed in 1942 by Paul Friedrich Pelshenke who later received the Thomas Burr Osborne Medal. It needs additional yeast with a high amount of storage leaven up to 20%.

    BP 190 for 3 hours at 35°C.


    was a necessary after the lack of resources because of the Secound Great War and a baker in the town of Bonn put down in writing the procedure in 1949:

    1. BP 300 for 3 hours at 22-24°C.
    2. BP 300 for 3 hours at 22-24°C.
    3. BP 300 for 3 hours at 22-24°C.
    4. BP 215 for 8 hours at 22-24°C.
    5. BP 265 for 3 hours at 30-32°C.

    A very effortful procedure.

    Monheimer Salzsauer

    was developed in 1958 and combines the simplicity of a single step procedure with the aroma development of a three-stage sourdough. The flour is mixed with water at 45°C and immediately cools down to 35°C. Progressively during the fermentation the temperature should go down to room temperature of 20°C. With a high amount of storage leaven of 20% there are enough microorganisms that 2% of salt can suppress their proliferation and improve the development of aroma for up to 72 hours.

    BP 200 for 18-24 hours at 35 to 20°C.

    Detmolder Stufensauer

    has a one, two and three step version, developed by a federal research institute in the 1960s in the town of Detmold. The single step version is popular because of its simplicity.

    BP 180 for 15-25 hours at 26-27°C.

    Weinheimer Qualitätssauerteig

    was developed at the academy for German bakery trade in the 1970s in the town of Weinheim to improve the Detmolder. The complex temperature control was feasible in laboratories but prevented the use for hobby bakers. The self-heating of the microorganisms was also never considered before. It needs 10% of storage leaven.

    BP 180 for 16 hours at 28°C.

    The sourdough will progressively cool down to 23°C, above the room temperature. Using only 2% of storage leaven increases the time to 40 hours.

    There are some more but I will leave them out because their history and development are uncertain. Generally the steps of a sourdough can be classified into 5 steps:

    1. starter sponge / storage leaven (if dried)
    2. natural leaven
    3. first leaven sponge
    4. secound leaven sponge
    5. ripe leaven sponge

    Step 22: Lactobacillales, Acetobacteraceae, Yeast

    In many recipes and explanations about sourdough you will be told that it consists of lactic acid bacteria and acetic acid bacteria. This is actually wrong. There are homofermentative lactic acid bacteria (hoLAB) which metabolise glucose only to lactic acid, and heterofermentative lactic acid bacteria (heLAB) which can also metabolise glucose to acetic acid. True acetobacteraceae need oxygen and ethanol to produce acetic acid. The full list of microorganisms in a sourdough can be found here. When you read an explanation about sourdough and it says it is optional if you pour away the hooch (which is water with ethanol), it is better if you do it. It decreases the chance acetobacteraceae proliferate in the sourdough and produce formic acid or other bad tasting chemicals. The various bacteria have different pathways to metabolise energy from molecules and therefor produce different molecules for aroma and taste.

    The main difference between the yeast and bacteria is that the latter propagates by cell division while the yeast spawns by budding.

    (The 2 yeast pictures were provided by my friend Ben from the Biobus.)

    Step 23: Positive Impacts on Sourdoughs

    The microorganisms like it warm, hoLAB prefer a temperature of 30 to 35°C (85-95°F), while heLAB produce acetic acid at 20 to 25 °C (68-77°F), but temperatures above 40°C (104°F) are deadly for both. Keep in mind that fermenting microorganisms also produce heat. A compost of rotting garden waste can heat up to 70°C (158°F). These temperature ranges are guideline values for hobby bakers because of the big range of microorganisms that can be in a sourdough. The optimal temperature for growth of yeast is 28°C while the perfect temperature for fermenting is 32°C. Organise the resting places of your sourdough according to your living style. During the day your bedroom has probably 20°C while your kitchen during preparation of dinner is closer to 28°C. Your basement is at 15°C while your boiler room has 35°C. Use a thermometer and find your best places to let the dough rise.

    Sourness. The name gave it away, right? Additionally I want to explain that lactobacilli produce acid until a pH of 3.6 is reached and then start reproducing. If it rises higher than 3.8 for example after feeding the sourdough, then they stop reproducing. The amount of starter sponge given to your leaven affects the pH and has immediate influence on the activity of enzymes like amylase.

    Stirring the sponge starter spaces the waste products of the microorganisms and food that is left. Generally it evens out the distribution inside of the sourdough and improves living conditions.

    Clean Water. I only use non-carbonated mineral water for my storage leaven because I am going to eat the result anyway. It is not like cooking water that I pour away. This way I don't have to think about chlorinated tap water.

    Hygiene. Always make sure the containers, tools and your hands are washed, rinsed and dried thoroughly. Most tutorials and explanations about sourdough will show you a picture with a glass jar and a strapped cloth on top. Take a canning jar like in picture 2 and just lay the lid on top. Gas can get out and no dust can go in. The sourness keeps all other microorganisms away why would there be a need for a cloth filter?

    1% salt. Some recipes ask for 1% salt during the fermentation. This inhibits proliferation of the yeast while the LAB can do their job.

    Step 24: Negative Impacts on Sourdoughs

    Many recipes will ask you to use wooden or porcelain spoons and to avoid anything made from metal. These hints come from a time when people used silver or copper spoons. Modern spoons made of stainless steel are able to withstand the low acidity of a sourdough, but don't take my word for granted. Another aspect is the oligodynamic effect, which destroys microorganisms when they come in touch with metals. The effects remain scientifically undetermined or are too complex to explain in this instructable, but to summarize and simplify, all active biological molecules have a charge and the touch of metal gives them a short-circuit.

    For a similar reason the container for a sourdough should not be a clay crock. The minerals and metal oxides in the clay could be dissolved by the low acids in a sourdough and then cause health problems. Unglazed stoneware could transpirate the water out of the container and destroy the sourdough.

    Microorganisms have neither skin nor fur and sun rays can easily destroy their DNA or heat them up. Find a shady spot that is still above normal room temperature. My sourdoughs thrive behind my computer, right in front of the outlet of the fan for my chassis. Since my parents are retired and live nearby, another good place is behind their TV.

    If you want to start a sourdough from scratch with microorganisms from the air around you, make sure the air is free of pollution. If you live in an old wooden cabin that was treated with wood preservatives, or by the sea with a lot of spume creating aerosols, or in a permafrost region, then don't expect vital spores of microorganisms in the air.

    2% salt. In the picture above you can see the impact that salt has on the microorganisms in a pizza dough. On a smaller scale an osmotic pressure destroys the microorganisms. The same happens when big sugar crystals dissolve too slowly in water.

    Stirring the leaven when you want it to grow will release the gas that you wanted to trap for the baking procedure. When a recipe asks you to let it rest, then be patient - there is nothing to see here, move on please!

    Step 25: Feeding a Sourdough

    Now that we know positive and negative impacts we can conclude the effects of feeding a sourdough. The pH-level decreases and allows reproduction of yeast. The higher the amount of starter sponge the lower the temperature can be. The food chain gets a reset and yeast can produce alcohol etc.

    There are 4 types of feeding for a sourdough:

    1. when you start one from scratch
    2. when you want to keep it alive
    3. when you refresh it
    4. when you are preparing a bread

    In case 1 you will feed it every day with the same amount of flour and water. If you want to keep the bacterial culture for your next project, you can feed it once per week in the morning and let the microorganisms proliferate throughout the day. In the evening then you put it into the fridge and stir it in the middle of the week. Sometimes you have to refresh the sourdough and add a small part of it to a new mixture. In case 4 you are feeding it according to a recipe and have different values of flour and water.

    Step 26: 123 Method

    A very simple way to make bread from sourdough if you don't have a recipe:

    1 Sourdough + 2 * the water + 3 * the flour + 2% salt

    If you have 200grams sourdough you add 400ml water and 600grams flour. The salt percentage is based on the amount of flour. Then treat the bread as usual with folding, resting and bake it the next day at 230°C (446°F) for 30 to 40 minutes.

    Step 27: Sourdough Discard

    Sourdough instructions ask you to discard half of the dough when you refresh it. This is only done when you are about to create a sponge from scratch. If you have a successful starter sponge on your counter top, don't throw the discard away! There are actually many recipes which make use of misfit sourdough. Add butter and you can make crackers, add it to a soup and you have kyselo. Add it to pancakes, pizza, pasta and pastry. With this instructable you will hopefully gain the knowledge to confidently use sourdough in many of your recipes.

    Kyselo was so widespread in the eastern europe region, there was a saying 'with Kyselo you wake up and with Kyselo you go to bed'. Sauté some onions in a cooking pot, add broth, add sliced mushrooms and then just add sourdough by the spoonful. The sourdough turns in the hot water into something like marrow balls. Serve with herbs and boiled eggs, tasty.

    Step 28: Why You Should Eat Sourdough Bread:

    A bread made with sourdough has a better digestibility than bread made with just yeast. The blood sugar level isn't heightened by just one type of sugar and therefor delivers continuously energy. The bread itself has a higher elasticity, the crumb is softer and there is no taste of yeast. Actually yeast has been used to such an extend that some people become allergic. In the following 4 steps I will elaborate more reasons to advocate for sourdough bread.

    Step 29: Nutrition

    The first roller mills were used to break the grain and then millstones would regrind this into flour. Then other rollers were developed to take that job as well. Nevertheless the trend did not stop because they added more rollers and were able to break down everything even further and therefor gained more flour with every step. Yet the fast steel rolls develop heat which destroy the vitamins. Allegedly even the common pest infestations could not sustain in the new white flour. But not just them, also our birth rates were affected and the negative trend was only reversed when the Secound World War changed the diets due to food supplies and food crises. This inspired many scientists for researches about organic/health/whole foods and led to improvements in the milling processes.

    Nowadays vitamin supplements are added to the white flour, but these only contain the most prominent molecule of each vitamin. In fact there are many molecules for every vitamin which are in the range of having a similar structure and a similar effect, the vitamers. Their coexistence helps the whole process the vitamin assists, helps their reuse and stability.

    The amount of vitamin supplements can be controversial because too much can cause a hypervitaminosis. Since pizza is considered a vegetable for school lunches in some countries, it comes as no surprise that some food brands boast too many vitamins. This can lead to a product ban in countries with a generally healthier food supply.

    Microorganisms can produce their own vitamins, mainly the B vitamins for cell metabolism. If you use sourdough for your bread, you get a fresh delivery of most B vitamers and an acidolous environment to protect them. The improved crust can deal much better with high temperatures during the baking procedure and the sour crumb inside keeps 83% of the vitamins intact. The acidolous environment also helps the proliferation of good bacteria in your digestive system. Some people like to drink those fancy probiotic yoghurts with health beneficial bacteria to improve their digestion, but why not send a first class caravan down there to improve the intestinal flora right from the beginning?

    Step 30: Shelf Life

    The picture shows a slice of rye bread that was left on my kitchen counter for 2 weeks. It got a bit dry and the crumb shows breakages, but there is no mould. I could still crisp it up. Sourdough bread is also said to reduce the effects of ergot, coliform bacteria, coccus, penicilium, aspergillus, and so on and so on.

    If you are single then buying sourdough bread is a better option for you because a normal bread usually goes bad before you could eat the whole loaf.

    Step 31: Rope Disease

    Long ago a big problem for bakeries, the rope disease(source German) destroys the structure of the breadcrumb into slimy filaments which look like a rope ladder. Rope spores are mostly from the bacteria Bacillus subtilis (also mesentericus, subtilis, natto) and their fermentation spoils the bread with a bad smell, also reducing the shelf life drastically. During the baking process the bacteria die in the heat, but the spores survive. When the bread is cooling down, the spores find a warm environment and germinate, effectively making the bread unfit for consumption within 24-48 hours. The wide use of pesticides in agriculture had made this disease a chapter of the past. Because the contemporary demand for healthy and organic food has reduced the usage of pesticides, it enables the growth and spread of these microorganisms again. Interestingly the same bacteria is used in Japanese fermented Nattō beans, which are considered very healthy.

    I did not try to simulate the rope disease to get pictures because it is said that once your kitchen/bakery is infected, it may be inoperable for months because the spores can survive several disinfections and fumigations. The provided picture was used with friendly permission by ZHAWInstitute für Lebensmittel- und Getränkeinnovation, by Prof. Fieseler.

    Of course you already made an educated guess for a solution to slow the growth of Bacillus subtilis in your own kitchen, and yes besides hygiene it is the acidulous sourdough. If you want to use more organic food you have to use "organic" solutions to prevent the diseases which come along with it.

    Step 32: Phytic Acid

    Originally grain has the task to start a new plant by turning into a seedling. To have all the needed resources at start, phytic acid is a storage molecule for minerals in the grain. This molecule is just so prone to attracting phosphorus, calcium, magnesium, iron and cink, that it can prevent their absorption in the intestines and cause a deficiency for your body. If you ferment your bread with sourdough, the phytic acid can be broken down and improve the nutritional value of your bread.

    Step 33: Comparison Yeast and Sourdough As Leavening

    Yeast produces more CO2 and is a faster leavening than sourdough but therefor unforgiving. If you look at the beginning of the animation above you can see how the growing dough first fills out the container, then more and more bubbles appear at the wall. This is why you let the dough rise in a bannetton and then for a short while in your bread pan. You want the air trapped inside of your dough and then the dough in a seamless shape coming out of your bread pan. If you let the dough rise in your bread pan for too long, then bubbles appear between the dough and the pan, drive away the grease and the bread loaf will stick to the pan like in picture 4. Whereas in sourdough only the heLAB produce CO2 when the temperature is 20-25°C. But wait, there is yeast in sourdough! Yes, but only while the hoLAB produce lactic acid. When the temperature falls and the acidity grows so much that mainly the heLAB are active, the yeast is inhibited.

    During the baking process most of the alcohol the yeast produced evaporates. Up to 0.1% of the weight of a bread loaf can still be alcohol. It is not enough to be dangerous for pregnant women or children, but if you are a sober alcoholic, have pancreatitis or hepatitis and need to avoid alcohol by all means, then sourdough can be an alternative depending on the advice of your doctor. But there are also good recipes with baking powder.

    The ethanol fermentation of yeast is simple and straightforward. There are no dead ends in the pathway. 1 sugar molecule is processed into 2 molecules ethanol and 2 carbon dioxide while the cell gains 2 ATP.

    C6H12O6 = 2 C2H5OH + 2 CO2

    The lactic acid fermentation of bacteria is complex. There are many different paths to produce energy and some will result in molecules no other LAB can metabolise. Since the acidity keeps other microorganisms away which could do so, these "dead end" molecules increase the variety of the taste and aroma of the bread. 1 sugar molecule is processed with 2 ADP and 2 free phosphates into 2 molecules lactic acid with 2 ATP and 2 water molecules (+2 protons).

    C6H12O6 + 2 ADP + 2 Pi = 2C3H603 + 2ATP + 2H20

    Step 34: Preservation of Sourdough

    When you go on a holiday and don't find a babysitter for your sourdough, there are several ways you can use to preserve it. The methods can also be used to have a backup in case anything goes wrong with your active one. My personal favorite is to add flour to make it viscously. Then a spoonful into a glass jar with a clip lock and it can last for 3 months without any mould, still being able to be used as a sour smelling 2% storage leaven. In the following 2 steps I will explain my other 2 favourite preservation methods, gersteln and desiccation.

    Step 35: Preservation: Gersteln

    Gersteln is the German word for a preservation process of sourdough. You overfeed it with so much flour that the microorganisms become naturally inactive in the absence of water. But you need to prevent lumps which contain water reservoirs. If you think the last expression is too bold, for microorganisms a drop of water is like a whole planet. Press the floured sourdough through a sifter to reduce the size of the lumps and add flour until you think most water reservoirs are in a drought state. Then the microorganisms are in that state as well.

    Step 36: Preservation: Desiccation

    Alternatively you can spread the sourdough on parchment paper with a dough scraper and let it dry in a warm place. Remember, not above 40°C (100°F) and not in the sunshine. Interestingly, before the sourdough is finally all dried out, the last wet spots will smell pretty bad. Apparently the heLAB are longer active than the hoLAB and this method could be improved by putting the paper into the fridge when it starts smelling. When everything is all dried out, bend the parchment paper from beyond and the desiccated sourdough drops off easily. Then fill it into a jar but close it with a strapped cloth. If you close it with a lid there will be mould.

    Step 37: Adapting a Sourdough to a Different Flour Type.

    When a recipe asks for a wheat sourdough but yours was made with rye, there is no need to make a new one or always have both types of sourdough around. You can either still use the rye one or permute it in 2 simple steps. Take 10 grams rye leaven and mix it with 50 grams wheat flour and water. Let it rest between 12 and 24 hours. Then take 10 grams of the wheat/rye leaven and mix it again with 50 grams wheat flour and water. After 12 hours you can now use 10 grams to create a first leaven sponge, the amount of rye is lesser than 0.01%. Of course this method also works the other way around.

    LeavenWheat FlourWaterRye Percentage
    rye starter sponge
    wheat/rye mix50grams50grams0.04
    wheat starter sponge

    (The rye storage leaven consists of 5 grams water and 5 grams rye flour.)

    Step 38: Malting

    Maybe you want to feed your sourdough neutral food. You can now either buy yeast nitrogen base which is used in laboratories to feed it in petri dishes or you can use a mixture of maltose and glucose. If you can't buy malt flour or malt extract, you can make it yourself. Buy grain either in an agricultural or organic market, or a health food store. Then soak the grain in water for 12 hours, drain it, and wash it every 12 hours with fresh water to prevent mould. Every time you wash the grain you will find broken ones which you should throw away. On the third day you should see 3 white threads coming out of the grain.

    Step 39: Dehumidify

    It is important to use the grain before the seedling becomes green. Dry the sprouted grain in your stove at 70°C for 1 or 2 hours.

    Step 40: Kilning

    Then we heat it up to 160°C for 30 to 60 minutes. After 30 minutes you need to check for the colour of the grain and the smell. Grind the malted result and feed your sourdough with it.

    Step 41: Lievito Madre

    In some of my instructables people told me they don't have access to fresh yeast in their supermarkets.

    Lievito Madre is the Italian way to have always access to yeast at home. It is a mild sourdough mainly populated by yeast. It takes 25 days to prepare but after that time has passed you have daily access to yeast or a good way to store it for a week in the fridge.

    (Allegedly the Persian Khamir Torsh is the same, but it is just a sponge dough.)

    Step 42: Recipe LM

    • 200 grams flour (1.7 cups)
    • 100 grams water (0.7 cup)
    • 20 grams honey (1 tablespoon)
    • 20 grams olive oil (1 tablespoon)

    Other recipes don't use honey but a ripe banana or low fat yoghurt. The flour should be either wheat type 550 or spelt type 630. Mix the ingredients into a dough, cut crosswise into the top to enlarge the surface and then brush the top with olive oil. Let it rest in a container and cover the lid. Place it in a dark spot at room temperature.

    Step 43: 1st Day:

    On the first day you do nothing but observe it. Some of the olive oil might have gathered in one of the folds, that doesn't matter. The dough has a small activity.

    Step 44: 2nd Day:

    The activity increases, but it is still very low.

    Step 45: 3rd Day:

    Now you refresh it. Take 100 grams from the dough, add 50grams of water and 100grams of flour. Slit crosswise and brush the top, place it in a new container.

    Step 46: 4th Day:

    The activity is getting higher.

    Step 47: 5th Day

    The LM has increased in size, refresh it with 100grams of the LM, 50grams water and 100 grams flower. This time you put it into the fridge. Take a longish container because the LM can grow much more now. I took an herb container which I received as a present but never used. Slit crosswise, close the lid and let it rest in the fridge.

    Step 48: 10th Day

    Take 100grams LM, add 100grams flour, 50grams water, knead it into a ball, clean the container, slit crosswise and brush olive oil on the top, back in the fridge.

    Step 49: 15th Day

    Feeding time! The dough is now very flexible and fluid. Take 100grams of the LM, discard the rest, and add 100grams of flour, 50 grams of water. This time there is no need to brush it with olive oil. Put it back into the fridge.

    Step 50: 20th Day

    The LM has now a consistency like honey and even static properties. Again 100grams LM with 50grams water and 100grams flour. From now on there is no need to knead it into a scoop. Back into the fridge in the cleaned container.

    Step 51: Test It

    I took 100grams of the discard and mixed it with 50grams of flour. The same with my starter sponge.

    Step 52: Bake It

    After fermenting both mixtures overnight I baked 2 buns with them. The sourdough mix has a lot of bubbles but an even level in the mould. The LM mix shows typical conglutination and an uneven top. The yeast bends outwards while the sourdough falls inwards. The yeast has no taste while the sourdough is full of flavour but with a poor structure.

    Step 53: 25th Day

    On the 25th day it should be ready for use. The distribution of the small bubbles indicates good leavening power. Five days have passed and it needs another feeding of 100grams flour and 50grams water, back into its container and back into the fridge.

    Step 54: Lievito Discard

    The Lievito Madre should now be useful for baking and I want to try it with a bread. I needed 200grams LM for the recipe and added the appropriate amount of water and flour, then rest overnight for 12 hours.

    Step 55: Lets Try the LM

    During the night the LM has doubled its size and is obviously complete. I took the 200grams I had prepared the day before and filled the container with 380grams water. In a mixing bowl I added 15grams of salt and 600grams flour di farina tipo 0, then added the liquid mix..

    • 600grams flour
    • 380grams water
    • 200grams LM
    • 15grams salt

    .Cover the mix with a kitchen towel and let it rest for 2 hours. If you are experienced in bread baking, fold the dough meanwhile to spread the air bubbles. Otherwise just turn the dough over after resting time. Preheat the stove to 230°C (450°F).

    Step 56: Result

    Put the dough into a slightly greased casserole and bake it 30 minutes at 230°C with the lid closed. Then remove the lid and bake it for another 20 minutes. I need to improve the handling of the dough to enhance the spreading of the air bubbles, but I'm happy with the result of a bread recipe without any added yeast.

    Step 57: Hermann the German Friendshipcake

    If the Lievito Madre is still too sour for your taste, have a look at Hermann cake. After 10 days of stirring and feeding the Hermann dough, you have a foundation for a wonderful cake that tastes neither sour nor too sweet. It is similar to Amish friendship bread and also shared like a chain letter, given to the sick and needy. Hermann has two brothers Siegfried and Robert, while Hermann is prepared with milk, Siegfried needs buttermilk and Robert likes yoghurt. There is a cousin called Werner, but he is a pure rye sourdough.

    In the following steps I will show you how to start a Hermann on your own and then the 10 day routine of fermentation. There are many many different recipes for the maintenance of a Hermann but this one is actually from a company publishing and testing recipes for cakes.

    Step 58: Preparing Hermann

    Prepare a container that fits into your fridge and can hold 1.5liters (50 ounces). Take 150ml lukewarm water, add 100grams wheat flour, 1 tablespoon of sugar and 2 teaspoons of dry yeast. Stir carefully and let rest at room temperature with the lid closed.

    Step 59: Sparkling

    The next day stir the mixture occasionally.

    Step 60: Hooch

    On the secound day there is probably some hooch floating on top of your dough, stir it at least twice that day.

    Step 61: Start of the Routine:

    (Now we have a Hermann dough at the beginning of the 10 day routine.)

    The first day you have to give Herman a break and then stir daily the next 4 days.

    Day 1: rest

    Day 2: stir

    Day 3: stir

    Day 4: stir

    Step 62: Day 5: Feed Hermann

    150 ml milk (2/3 cup)

    150 gram sugar (2/3 cup)

    100 gram flour (1/2 cup)

    Don't forget to stir!

    Step 63: Stir?


    Day 6: stir

    Day 7: stir

    Day 8: stir

    Day 9: stir

    Step 64: Day 10: Feed Hermann

    150 ml milk (2/3 cup)

    150 gram sugar (2/3 cup)

    100 gram flour (1/2 cup)

    And stir it!

    Step 65: Hermann Can Be Shared Now

    Adding all the ingredients together we invested ingredients of 1090 grams into the dough (290g starter + 2 * 400g feed) and the final result has 985 grams. Around 105 grams were fermented into CO2 or were partially lost during transfer.

    Now split the dough into four equal parts. One is for the cake you bake tomorrow, one is for your next Hermann procedure (Step 61) and two which are for friends who you also give this explanation.

    Step 66: Hermann Cake

    Let's make a cake from the completed Hermann dough.

    • 2 cups flour (250grams)
    • 1 cup milk (150grams)
    • 1 cup sugar (150grams)
    • 1/2 cup vegetable oil (100grams)
    • 3 eggs
    • 1 package baking powder
    • 1 package vanilla sugar
    • 1 pinch salt
    • 1 portion Hermann

    Mix the flour with the baking powder and vanilla sugar, sift both into a bowl. Add all other ingredients, mix with a food processor and fill into a cake mould. Bake for 45-55 minutes at 180°C (356°F).

    Step 67: Wunderbar!

    The result is wunderbar! The cake is not too sweet, it is not too wet, it is a spongy and tasty cake that you can use for any type of icing and coating. I need to adapt the amount of baking powder though, the dough had a bit too much leavening power.

    Step 68: Total Failure

    It all didn't work for you and you still have no sourdough? You live by the sea? In a space station? Well then of course you can buy a starter online. You can find many entries in online shops, amazon or ebay.

    Or you can ask for a free one from Carl Griffith's 1847 Oregon Trail Sourdough Starter. Just follow their instructions and send them an envelope with your address and postage.

    Step 69: Glossary

    Abbreviations that I used:

    starter spongeactive sourdough culture used to start a sourdough
    storage leavendried sourdough culture
    natural leavensourdough started by mixing water and flour
    first leaven spongesourdough to grow in volume
    secound leaven spongesourdough to increase acidity
    ripe leaven spongedough ready to be baked
    hoLABhomofermentative lactic acid bacteria
    heLABheterofermentative lactic acid bacteria
    LMLievito Madre

    Step 70: Epilogue

    Hopefully this instructable was helpful for you and comprehensible. The length is a bit too long and I encountered some bugs & crashes during the creation. If you find mistakes just let me know in the comments and I will fix them. The instructable is my entry in contests, if you like to support me, click on the "Vote!" button on the top right.

    Thank you and enjoy your sourdough!

    Explore Science Contest 2017

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    Explore Science Contest 2017

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