Acetic acid

Acetic acid is the ethanoic acid (CH3COOH) with a molecular weight of 60,05 kDa. It is produced by the oxidation of ethanol by lactic acid bacteria and is the main constituent of vinegar. Acetic Acid is mainly produced in sourdough between 20°C/68°F and 25°C/77°F. Acetic acid is responsible for the tangy flavour of your sourdough or your sourdough bread.


Acidity in sourdough indicates the total amount of organic acids. That's the combination of lactic acid and acetic acid present in the dough. A titration method is used to measure acidity.


An element is considered active when it is alive and has an impact on its environment. For example, an active sourdough has living micro-organisms that produce CO2 and aromatic molecules, giving volume and taste to the bread. When a sourdough is dried, the micro-organisms are alive but inactive; they will be revived by adding water.


A living organism is an organism in interaction with its environment. It’s following the cycle of life: birth, growth, feeding on some source of energy, producing wastes, reproduction and death. As a consequence, it has an impact on its environment, just like a living sourdough has an impact on the texture and organoleptic properties of the breads.


Autolyse is a way to let the flour rest with water before the actual mixing. The proteins in the flour will start to absorb water and as such allow a higher hydration of the dough. the enzymes naturally present in the flour will also start to create the biochemical reactions. in general the recommendation for an autolyse is going from 20 minutes up to two hours. To execute it well it's a matter of blending the water and flour together and cover it. No other ingredients should be added. Sometimes sourdough starters are already included. It is not a necessity. Unless you want to increase the amount of organic acids. Those will make the bread more sour.



Backslopping is a technique used to prepare a batch: a combination of products that will ferment together. It uses the fermented substrates from the previous batch in the new batch of raw materials in order to promote successful fermentation. This is the main technique used to refresh a sourdough


Biga is a type of starter used in Italian baking, resulting from a blend of flour, water and active dry commercial yeast. Because it has a hydration of only 50 to 60%, a biga is usually very firm and has a nutty taste. Many popular Italian breads, including ciabatta, are made using a biga because it provides a light, open, aromatic texture with holes, and it helps to preserve the bread.


Commercial yeast

Commercial yeast or baker’s yeast is the term used for strains of Saccharomyces cerevisiae fungus that are selected, isolated and propagated. They are used as a leavening agent in bakeries, which means that they make the dough rise thanks to their ability to ferment sugar and produce carbon dioxide. Commercial yeast is sold in two forms. Active dry yeast is alive but inactive due to lack of moisture, while compressed fresh yeas is alive, and therefore needs to be conserved in the fridge.



Caused by living organisms, fermentation is an anaerobic process. There are two types of fermentation: lactic and alcoholic. Each metabolic pathway provides energy to the organism by transforming an organic molecule: pyruvate is converted into CO2, lactic acid, and CO2 and ethanol in alcoholic fermentation. This process is used in many food applications to add taste and texture: lactic fermentation of bacteria in cheese, yogurt, and sauerkraut; alcoholic fermentation of yeast in beer and wine; alcoholic fermentation of yeast and lactic fermentation of bacteria in bread…



Gluten is a protein found in wheat-type cereals and is responsible for the structure and texture of bread. When the ingredients are mixed, a 3D gluten network develops in the dough. This network retains the CO2 produced by micro-organisms during fermentation. As a consequence, the bread gains volume and keeps it until baking, when the gluten network becomes solid. In the finished baked goods, gluten is what determines the density of holes in the crumb structure.
During the sourdough fermentation the gluten network is partially converted into amino acids.


Lactic acid

Lactic avid, or 2-hydroxypropionic acid, has a molecular weight of 90 -07 kDa. It is produced by lactic acid bacteria or mould fermentation of sugar substrates. Lactic acid can also be produced by muscles at the beginning of a sudden effort, as seen in animals and in people. In food, it is mainly found in milk products, like yoghurts, but also in sourdough.


Lactobacillus is a type of lactic acid bacteria that ferments sugar substrates, like glucose, sucrose, lactose, starch, or waste materials containing them, and produces lactic acids as a result. There are several basic types of traditional fermented products based on Lactobacillus, including yoghurt and some probiotics. Lactic acid bacteria are responsible for wide-ranging diversification in the flavor and texture of food products, due to their fermentation of raw materials used in food.



A micro-organism is an organism that is too small to be seen by the naked eye. Also called microbe, this category includes bacteria, viruses, protozoa, some fungi and some algae. Through the sourdough library project we have already identified more than 900 strains. For yeasts we have found the following Genus: Saccharomyces, Kazachstania, Wickerhamomyces, Metschnikowia, Torulaspora, Pichia and Lachancea. As Lactic Acid Bacteria we found; Lactobacillus, Enterococcus, Leuconostoc, Pediococcus, Weissella, Micrococcus, Streptococcus

The yeasts are mainly responsible for the production of gas to make the bread rise as well as the production of esters. These are small flavour components that will change from species to species. The LAB (lactic acid bacteria) are mainly responsible for the production of organic acids. The two major ones are lactic and acetic acids although they can produce some gas under certain conditions.

The picture shows a combination of a starch granule, gluten, yeast cell and a LAB in a sourdough.


Mixing is the combination and hydration of two or more ingredients until they're homogeneously dispersed throughout the dough. In bread, it also provides the energy necessary for gluten structure development, and incorporates oxygen for oxidation and yeast activity.


Organic acid

An organic acid is a chemical compound that contains carbon atoms and has acidity caused by the carboxyl group -COOH. Organic acids can be found in many food applications: acetic acid in vinegar; ascorbic acid (vitamin C) in orange juice; lactic acid in yoghurt; oleic acid in olive oil; palmitic acid or 'palm oil' in chocolate spreads etc...

Organic food

Organic foods aim to have a low impact on the environment. Specific legislation depends on the country, but most or all of the ingredients in the product must be the result of sustainable agriculture. Usually it means that no pesticides, no synthetic chemicals, no antibiotics, no growth hormones, no GMO ingredients and so on have been used. Moreover, organic farming practices try to avoid wasting natural resources. For example, in the European Union, all verified organic products must have this label. If an EU product does not have this label, it is not certified organic.



pH is a figure expressing the acidity or alkalinity of a solution on a logarithmic scale. On this scale, 7 is neutral, while lower values are more acidic and higher values more alkaline. A low pH has higher number of proton type molecules (H+) and very few hydroxide ions (HO-). Conversely, a high pH has very few protons and many hydroxide ions. The pH of a sourdough should be below 4.2. That is the barrier where all pathogens that can be present in a sourdough are killed. The pH of a mature sourdough will balance between 3.5 and 4.2.
Nevertheless pH is not the absolute quality measurement. The TTA, or Total Titration of Acids shows how much organic acids are present in a sourdough.


Poolish is a type of starter, made from flour and water added in equal quantities (1:1 ratio, 100% each), with the addition of active dry commercial yeast. Because of the high percentage of water, it results in a sponge, typically quite wet. Polish in origin but mostly used in French baking, it makes the bread lighter and less acidic than classic sourdough breads.


In bakery, proofing, or proving, is the spare time that allows the dough to rise thanks to the fermentation of the micro-organisms. It happens twice: the first proof takes place between two kneadings and the second and last proof between kneading and baking.



A sourdough is a type of starter. It is called Levain in French, Levito madre in Italian, Masa madre in Spanish, Sauerteig in German, Zuurdesem in Dutch. It is a mix consisting solely of flour and water, which results in a complex microbiological ecosystem that occurs naturally in the dough and ferment. Bacteria and yeast originally present in the flour and in the external environment produce lactic acid, acetic acid, CO2 and ethanol. It makes the bread rise before baking, give it unique organoleptic properties, and prevents mould development. Sourdough properties vary depending on the flour used (wheat, rye...), and the form in which the rising agent is added (liquid, powder, starter...). They can be used for many different applications, from crusty bread, to soft bread or Viennoiserie. The pH of a sourdough should be below 4.2. This guarantees that all pathogens are killed and the sourdough is safe to use.

Sponge & dough process

A sponge & dough process is a two-step baking method. First, some of the ingredients are mixed ahead of time and left to ferment, typically overnight. We call this a starter, also known as sponge or preferment. After fermentation, the sponge is mixed with the rest of the ingredients to make the dough. As a consequence, since the fermentation process is longer, it generally releases more complex flavours in your loaf.


A starter is also called mother dough, pre-ferment, or sponge. It is a picture of flour and water, sometimes with the addition of yeast. It is mixed and left to rest for up to three days to allow a longer fermentation of the dough. It results in a highly distinctive taste and texture in the final baked products. Big, poolish and sourdough are three examples of bread starters.

Starter culture

Starter cultures are preparations of live micro-organisms of their resting forms which generate metabolic activity that has desired effects in the fermentation substrate: the food. These cultures may contain bacteria, yeasts and moulds. The resulting fermented food could include yoghurt, vinegar or sourdough.

Stretch and fold method

Stretch and fold method, or intermittent kneading or folding, is a kneading method which aims to maximize gluten development in a dough with minimum mixing time. It is conducted twice, in 3 steps: the dough must be extended, then folded from one side lengthwise, then folded from the other side (see drawing). Then start again in the other direction (vertically or horizontally).


Wild yeast

Wild yeast is a category comprising all yeast strains that occur naturally in the environment, especially in the air and on materials that have a high sugar content. For example, wild yeast can be found on the skins of fruits and berries (such as grapes, apples, or peaches); in the exudates from plants; in the digestive tracts of mammals and some insects; and even in deep-sea environments.