The Fresh Loaf

News & Information for Amateur Bakers and Artisan Bread Enthusiasts

Autolyse

Doc.Dough's picture
Doc.Dough

Autolyse

I am looking for technical papers that quantify, rationalize, and explain what is going on during autolyse. So far I have found only the observations/claims of Calvel about improving over-oxidized and over-mixed bakery products, and no writings that would pass any threshold of scientific (or even engineering) rigor.

Pointers would be greatly appreciated.

Doc

Mini Oven's picture
Mini Oven
Doc.Dough's picture
Doc.Dough

Thanks for the pointer. I did look but it is not worth digging in that pit.

The Italian article below is more on point.

bikeprof's picture
bikeprof

This is the Italian source:

https://www.dolcesalato.com/blog/2013/05/31/giorilli-ci-spiega-la-tecnica-dellautolisi/

Here is the translated text:

GIORILLI EXPLAINS THE TECHNICAL DELL'AUTOLISI

31/05/2013

The dough is one of the main steps in the preparation of bread and bakery products in general. From its quality depend to about 80% of the characteristics of the nished product, for which a correct execution of the dough has a fundamental importance in order to obtain an excellent nished product. There are various methods in the preparation of a dough. The most common are: direct , in which all the ingredients are kneaded in one step; Indirect, where he is rst prepared a Preimpastato as chariot or poolish made of our, water and yeast compressed who undergoes a fermentation at the end of which is inserted into the mixer and mixed with other ingredients. The dough can also be prepared by the method semidirect using the carry dough or a pre-ferment. Furthermore, there are various techniques such as the dough intensied, the hot dough etc .... It plays a 'particularly important technique of' autolysis . Its use gives the nal product a number of benets, mainly due to the characteristics of the dough, the consistency of which is very smooth, elastic, malleable, capable of absorbing more water. The nished product acquires a greater volume and its crumb is very developed and soft. There are also benets in terms organoleptic (taste and smell like) and storability. Before explaining the details of this technique, and the reason for which using this method will have the benets listed above, it is necessary to describe the dough processes in general. In any mixture, regardless of its method of preparation, physical-mechanical processes take place, colloidal, biochemical and microbiological.

1. The physical and mechanical processes

The rst stage is the formation of the dough that consists in mixing the ingredients and, providing energy (or manually or with the use of the kneading), forming a smooth and homogenous mass, which has a certain softness and a certain elasticity . The kneading is a very important process, from which depend the characteristics of the dough and its behavior both during fermentation that during cooking and, consequently, the quality of the nished product. You need to mix all the ingredients well, not only for incorporation in the dough evenly, but also because it is obtained by mixing friction and the union at the molecular level of the chemical components of the our and other ingredients, which form a homogeneous mass called " dough ". The main reaction of this step is the formation of gluten. The wheat proteins have different dimensions and during the dough the cohesion forces combine the molecules of different sizes, forming a plastic and elastic mass, called gluten. Not all proteins, present in the our have capacity to form gluten, but only those insoluble according to the classication of Osborne, with which all of the our proteins are divided into four groups according to their solubility and which are divided as follows

  • albumin (soluble in water)

  • globulins (soluble in saline solutions)

  • prolamins (soluble in alcohol)

  • glutelins (soluble acids and bases)

    Each of these fractions has different physical properties, they are also their different molecular size, which increases in going from albumins glutelin. The gluten is formed only by the two non-soluble fractions in water and in salt solutions (prolamin and glutelin), which are joined to each other under the action of water and of 'energy, supplied to the dough. The protein molecules of a our during the mixing, after joining between them, are ironed and are oriented so that the electronegative groups are subjected to the action of water. Then the protein content of a our and the amount of water required are closely related to each of them. The dough added water should never be in such quantity as to remain, even in part, free. The amount of water absorbed from mixing depends on several factors, such as the particle size, the protein content, the quality, the moisture of the our and the presence of other ingredients in the dough, the hydrometric degree of the environment and the degree of consistency you want to have the dough. The doughs containing more water must be kneaded longer, so that the water runs and tied the 'dough reaches optimum consistency. Also during mixing the dough appropriates a part of the air, it becomes less dense and softer. Oxygenate the dough is important not only to make it more soft and more elastic, but also to promote the fermentation process, because the oxygenation of the dough stimulates the vital activity of the yeasts. The oxygen thereby strengthens the gluten network, formed during kneading, it oxidizes the thiol groups of the our proteins, turning them into disulde groups. The mechanical physical processes that occur during kneading are to change in physical and mechanical properties (strength and elasticity) of the dough, they depend on the mechanical action of the mixer. The effort that opposes a kneading the dough is not always constant and will change according to the dough characteristics. By measuring these efforts from the beginning of mixing, you can highlight three periods:

    • the rst period, after mixing of the ingredients, the increase of the kneading effort and this is due to the formation of gluten that becomes increasingly rigid and therefore opposes a greater resistance kneader up to the maximum point, after which remain stable, and then you can highlight

    • the second period, when the effort of the mixer always remains constant. In this period the dough has the optimal characteristics (it is very smooth and the maximum extensibility). This is due to the fact that the mesh is gaining gluten dough extensibility, mind its resistance decreases, because it starts the reaction of proteolysis. In this period the dough is ready and should be removed dall'impastatrice, in fact is very elastic and does not stick to the walls. Continuing the operation will worsen its features.

    • the third period, ie when dall'impastatrice efforts are declining, the dough becomes more springs for overheating and excessive mechanical stress occurs and the rupture of the gluten network.

    For each mixture the time necessary to reach the optimal characteristics (second period) varies and depends on:

• on the strength of the our (the kneading time of a weak our is lower than the mixing time of a strong our, as it has a resistance of

less gluten mesh);

• the type of mix (soft, soft, dry). The soft dough must be kneaded more, they must have a higher nal temperature and be kneaded until it reaches the consistency of their top. Dry dough must be cold enough after the ìimpastamento, removed before dall'impastatrice, although they are not fully formed, because they generally are cylindered. During the calendering it is carried further warming the dough and it reaches its optimum consistency;

• the type of the kneading . For example, with a 'kneader "spiral" the dough is formed rst with respect to a' kneading machine with plunging arms, because the type "spiral" as more dough friction. The mixer "fork" is the one that gives less effort and in all types is the slowest. During kneading, the heating takes place, due to the type of the kneading, and other factors, which varies from 3 ° C to 18 ° C.

2. The colloidal processes

Mixing the our and water, it starts to form the very hydrated colloidal complex. The our proteins are capable of absorbing and connect the quantity of water 2-3 times higher compared to their weight. The proteins, which belong to the groups of the prolamins and glutelins (insoluble in water and in salt solutions), by absorbing water, swell, stretch and bind together with covalent bonds, disulde etc., Forming the gluten . In addition in the dough are created dipolar bonds, hydrogen (with water), ionic (caused by mineral salts, which in part are contained in the same our (phosphates, sulfates, chlorides etc ..) and in part added, such as sodium chloride (kitchen salt). the addition of salt in moderate percentage (around 2%), the better the strength and elasticity of the dough, the ability to retain the gas and ultimately the bread volume, while high amount of sodium chloride due to the formation of an excessive number of ionic bonds that make the dough too stiff and

rigid. the starch, whose quantity in the mixture is conspicuous, absorbs water and forms the electrostatic bonds with the gluten , creating a homogeneous mesh. Even the dough lipids (especially polar ones, such as mono- and diglycerides) have the ability to bind with proteins, forming the lipo-protein complexes, thus improving the extensibility and the retention capacity of gas by the dough.

The gluten mesh thus formed absorbs the water, liquids and gases present in the dough, not only on the surface but also in depth, which causes swelling of the gluten mesh itself. The dough can be imagined as a complex system which includes three phases: solid, liquid, gaseous.

The solid phase

The solid phase of the mixture is represented by the insoluble proteins (united between them in the gluten mesh), and the starch granules from the bran residue. The starch granules do not have the same capacity for absorption of liquids such as gluten (they only absorb 30-35% of water by their mass), and so not much increase their volume. However, whereas there is much starch in the our, the amount of water consumption will be more or less equal to that absorbed by proteins. The capacity for absorption of water by the starch granules increases with their damage during grinding (unless they are not excessively damaged, otherwise absorb less water). The residues of the bran are those which absorb the greatest amount of water (up to 800% of their weight).

The liquid phase

Besides water, the liquid phase belong all other substances which are in solution: the soluble proteins in water and in salt solutions (of albumins and globulins groups), the mineral salts and sugars, dissolved in water, respectively, , dextrin. Also the pentosans (gels) belong to the liquid phase of the mixture. The liquid phase can be located around the surfaces of the solid phases and also of being absorbed inside.

The gaseous phase
It is made from the forfeited from mixing during kneading and carbon dioxide produced during fermentation. A fragment of the dough can be represented as follows:
3. Biochemical processes

Are the processes of the transformation of lipids, carbohydrates, proteins and other chemical components of the our and the dough with the help of enzymes contained in the our and baking powder. The reactions that occur in the dough are numerous and complex. During the kneading you create different bonds (covalent, dipolar ionic, hydrogen, electrostatic etc.) Between the proteins forming gluten and other components (soluble proteins, mineral salts, starch, lipids, etc.). , building a uniform and homogeneous matter called "slurry".

Furthermore, with the help of wheat our enzymes, activated with water, in the dough begin the hydrolysis reactions of proteins and starch. Under the action of proteases, the proteins of the our begin disintegrating into peptides (the reaction of proteolysis), helping the dough to become softer and plasticabile. This process takes place in each dough, however, may be more or less active, it depends on various factors (enzymatic activities of the our, the properties of the gluten, dough temperature etc.). Also in the dough is the starch hydrolysis under the action of amylase, which begins kneading, but it develops more than anything else during fermentation, making the foods (sugars) to the yeast cells, and for this reason is of signicant importance. Even this process (saccariferazione starch) the action is liquefying the dough. Also they take place the reactions of transformation of sugars and lipids. The behavior of the latter has a dual effect: for themselves increase the extensibility of the gluten network and make it more pliable dough, if it is processed with the help of enzymes (lipase and lipossiasi) in peroxides (this process takes place partly and has a lower intensity) cause the opposite effect, because the latter make the gluten network stronger and more rigid.

4. The microbiological processes

The microbiological processes (which concern the microora of the dough) are: the multiplication of the yeast cells and lactic bacteria and also the alcoholic and the lactic fermentation below. During the kneading is active multiplication of these microorganisms, which begin to ferment during the rst fermentation (also called "bet") of the dough. The purpose of the fermentation is to obtain a dough that has the optimal properties for its forming, and below the leavening and baking. During fermentation continue the colloidal and biochemical processes: the starch granules and other components of the solid phase of the mixture continue to absorb gases and liquids; Furthermore, the CO gas phase increases for the formation 2 produced by the yeast, and then increase the volume of the dough and its softness. During fermentation, the change of the gluten properties: the proteins of the gluten molecules continue to swell by absorbing the carbon dioxide produced by the yeast, relaxing and bind between them, making the mixture more spongy, also it takes place the reaction of proteolysis , which makes the dough more pliable. The main processes that occur during fermentation of the dough are the alcoholic and lactic fermentation.

Autolysis. The process and chemical aspects

The autolysis is a special technique that allows you to take advantage of the self-evolution of the gluten characteristics. This system is practiced in three phases: initial mixing of the our with water; rest of the dough Autolytic thus obtained; and in the nal mix order. In the rst phase of the kneading it is dosed the basic ingredients (our and water (55%)), which are gently mixed (for example with the spiral kneading 5-8 minutes, only in rst speed). The dough thus obtained, subsequently undergoes the rest ( second phase ), which can last from 20 minutes to 24 hours. If the rest period is longer than 5-6 hours, it is advisable to add to the mix one part of salt and do not exceed 45-50% of water, the next storage should be carried out at a temperature of + 18-20 ° C. While for the fairly short rest period the dough is left to the environment, possibly in the same tub of the kneading. Finally it follows the third stage (the nal mixture), in which the missing ingredients in the recipe (yeast are added, malt, possibly water, salt), or other ingredients according to the recipe. The whole is mixed only in the second speed for the time necessary. The autolytic mixture can be used totally or partially (with a minimum of 20% dose).

The autolysis technique leads to the nal product, marked by three characteristics: a characteristic avor, a great development and a longer shelf-life. Also reduces the mixing time, the consistency of the dough becomes particularly smooth and malleable, it has an easier molding and the nished product has a higher volume, a better alveolation and greater softness of the crumb.

These peculiarities in the product are the result of physical, chemical and colloidal who take the eld during the rest of the dough. In this phase the gluten undergoes changes (lysis) to work of enzymes (in particular amylase and protease), activated by the water of the dough. Under the action of the amylase enzyme, as has already been treated, the starch is converted into sugars, providing more available sugars in the dough, thus facilitating the fermentation below and bringing to the nal product the best organoleptic characteristics (such as the taste and the most intense fragrance). The protease enzymes are the protagonists of the reaction of proteolysis, the reaction, which takes place in any mixture and takes development especially during the period of resting of the dough. With this reaction the gluten network of the dough is broken into smaller pieces, the protein chains thus obtained are getting longer, the dough takes on greater extensibility, become more malleable. The reaction of proteolysis may be more or less active on the basis of various factors (the structure of proteins (particularly gluten properties), the enzymatic activities of the our, the presence of certain substances in the dough, dough temperature etc. ..). We explore this topic:

The structure of proteins
Proteins are made from amino acids and can be disposed into shorter fragments (called peptides) under the action of the protease enzymes.

Proteolysis is the reaction to the disintegration of proteins. This reaction disintegrates the globular structure of the protein. The proteolysis happens in each dough, however, may be more or less active, it can involve more or less protein. As the reaction of proteolysis, the more springs will be more active will become the dough . Proteolysis, destroying proteins, involved in the gluten network, lowers its capacity for absorption of water and carbon dioxide retention. Then, the progress of this reaction decreases the strength of the dough and increases its extensibility. The activity of the reaction of proteolysis depends dall'attaccabilità of proteins by enzymes. The factors that determine the stickiness of proteins are the following:

The presence of certain groups (thiol or disulde)
The protein structure is quite complex, in addition to peptide bonds are present also other bonds, including, for example, those which involve

the two sulfur atoms, so-called the disulde bridges (-S = S). So, in the proteins you can highlight the groups thiol (-SH-) or disulde (-S = S ). A our, which have the most protein disulde groups (-S = S), has less stickiness. This meal will have a stronger and more robust gluten

(reinforced by disulde bridges).
However, the presence of thiol groups (-SH-), easily attacked by proteases, causes the formation of a more rare and weak gluten network.

denaturation

With the denaturation increases the stickiness of the proteins. The denaturation occurs when the protein, reacting to heat, lose the compact structure (globular) and are transformed into an intermediate position between the globular structure and brillar. With this process discarding the disulde bonds of the protein, whereby after them are easily attacked by proteases. The heat denaturation of proteins takes place in the dough prepared with the hot technique.

the quality of the wheat from which the our was produced

It regards the genetic characteristics of the grain (which determine the protein content and chemical composition of proteins) and climatic characteristics of its maturation (normally in warmer climates and dry the grains reach the highest protein values).

A special importance has the chemical composition of the gluten itself.

The proteins of the our, insoluble in water and in salt solutions, have the ability to form during the dough an elastic structure, compact and spongy, called the gluten . The force of the our more dependent on gluten properties.

The higher the content of the gluten, the stronger is the our . Gluten is the one, which supports the dough, practically performs the function of the load-bearing walls in a house. However, the amount of gluten does not determine everything, its characteristics are also important. The two ours may have the same amount of gluten, however, can be a stronger and the other weaker.

Gluten is composed of the prolamins (mostly represented by gliadin protein) and from glutelins (where it is present mainly glutenin protein).

The gliadin in contact with water form a sticky mass and uid, instead glutenin absorbing water, it forms a compact mass, elastic and resistant.

The wet gluten possesses the mechanical characteristics of any two proteins (gliadin is that the glutenin). Obviously, a our to be stronger must have a majority glutenins . If a our has a high amount of gluten, but this consists mainly from gliadin, the our can not be very strong, because its gluten is soft and slightly spongy.

The time of storage of the our

In a rested the our stickiness of the proteins decreases, however, in an expired our, is excessively high.

The enzymes protease

Proteases are enzymes, contained in wheat, able to undo the proteins. Proteases unmake the globular structure of proteins, without going to amino acids, as they have the ability to destroy all the peptide bonds .

proteases also can be found in the passive and in active form, according to the groups, contained in their structure (thiol or disulphide): Pr-S = S-Pr Protease in passive form
Pr-SH proteases in active form

Activators and inhibitors of proteolysis

Activators of proteolysis are substances that transform protease from passive into active form and favor with this reaction of proteolysis. Are the substances that weaken the our. For example, are part of the glutathione and cysteine, the protein nature substances, contained in the wheat germ and the yeast.

The inhibitors of proteolysis , however, are those substances, which transform the protease from the active in the passive form. Are the substances that strengthen the our. As examples of inhibitors of the proteolysis can list as peroxides, oxygen, vitamin C and also oxidants type potassium iodate (KJO 3 ) and potassium bromate (KB r O 3 ).

Also in the dough Autolytic takes an opposite reaction to proteolysis, ie the strengthening of the gluten network due to the action of air oxygen, incorporated by the dough during kneading. Under the action of oxygen groups of the gluten network (SH) are transformed into disulde bridges (-S = S), the gluten is strengthened, it becomes more elastic and can absorb higher amounts of water. This reaction takes development especially during dough (in the rst phase of autolysis and the last stage (the nal dell'impastmo)), to a lesser degree also occurs during the rest of the dough. During the rest of the dough the gluten mesh is transformed, thanks mainly to these two reactions (that of proteolysis and that of oxidation), the protein chains get longer, they swell by absorbing the air and the water, complete their hydration, so the dough during its nal processing reaches the top of its consistency in the shortest period, with the larger quantities of water.

All in all autolysis is a technique that gives the dough a particular extensibility, but at the same time improves the elasticity and the degree of water absorption, it also reduces the time and kneading dough is very smooth . This technique can be particularly useful for breadmaking with the natural yeast, or when they are used our, particularly resistant.

The Piergiorgio master Giorilli

Doc.Dough's picture
Doc.Dough

There are both oxidation and reduction reactions going on in the dough in response to many factors.  That much is clear, but it is not clear what specific "over oxidation" is precluded by use of an autolyse step. 

I found an interesting 2001 paper
(Proteolysis by Sourdough Lactic Acid Bacteria: Effects on Wheat Flour Protein Fractions ...)
that makes the case that LAB-derived proteases are more effective at breaking down gluten proteins than organic acids alone (lactic/acetic), and that different LAB express different proteases that attack different proteins with different levels of effectiveness.  The results are valid even though the focus of the study was human cereal intolerance.  It does not address the issue of why an autolyse step is uniquely valuable.

bikeprof's picture
bikeprof

I recently did a bunch of searching for good work that is also practically applicable on proteolysis.  I have about 5 articles (including the one you posted) among them a review article...but none clearly address the questions I have, which involve the dynamics of all the proteolytic mechanisms commonly found in sourdoughs...including the relative effects of temperature, acidity, and salt.

Part of the question for me involve the limits of salt's inhibitory effects, particularly as acidity increases (and typically, as I understand it, activates proteolytic enzymes).  I also haven't found a decent explanation of what acid actually does on its own that is proteolytic, and its own effects on gluten, independent of, and in combination with, enzymes in dough.

When I have more time, I can work on sharing the articles I have (a couple of which I got directly from Michael Ganzle)...

Doc.Dough's picture
Doc.Dough

Either here or by PM.

From what I have been able to find, the protease activity is a function of pH rather than acidity, but it is not clear (to me) whether it is a rate issue or a numerical density issue.

bikeprof's picture
bikeprof

thanks and will do...and I mentioned "acidity" meaning to leave it ambiguous between TTA and pH