Chapter 4 Fermentation.
After reading this chapter, you should be able to
* explain what fermentation is and why it is a very important step in baking.
* explain the different ways to use fermentation and how to control it to ensure consistent quality product.
* put into practice several retarding techniques.
* explain the connection between fermentation and flavor.
The baking process is a harmonious balance between the skill of the baker and the natural transformation that happens during fermentation. Fermentation begins when the baker joins together the two main components of bread: flour and water. With the addition of salt, yeast, time, and temperature, the baker balances all aspects of fermentation. It can be divided into two different phases: the handling period, when the baker physically works with the dough to mix, divide, and shape it, and the fermentation period, when dough characteristics are transformed. Both phases are critical to the final quality of the product. The style or path of fermentation dictates the bread's final flavor and aroma. To understand fermentation is to understand the baker's preference and expectations of the product.
Fermentation refers to the breakdown of compound molecules in organic substances under the effect of yeast or bacteria (ferments). Different types of fermentation are responsible for a number of products consumed in everyday life. For example, lactic fermentation is used to make cheese, butter, and some yogurts; acetic fermentation is used to produce vinegar from wine; and alcoholic fermentation is used to produce alcohol, cider, beer, and a number of other products.
In bread baking, fermentation occurs when some of the sugars or glucides (the group of carbohydrates that includes sugars, starches, cellulose, and many other compounds found in living organisms) naturally present in the flour are converted into alcohol and carbon dioxide under the effect of commercial or naturally occurring yeast and bacteria. This type of fermentation is categorized as an alcoholic fermentation. (See Figure 4-1.)
Wheat flour contains different types of glucides that are used at different times during fermentation. These glucides can be classified according to the complexity of their structures. Some are used as is. Other glucides with more complex composition must be degraded by enzymes, or organic substances with different degradation proprieties that either are naturally present in flour and yeast or are added during the milling process. (See Figure 4-2.)
[FIGURE 4-1 OMITTED]
[FIGURE 4-2 OMITTED]
Simple Glucides (Carbohydrates)
The basic simple glucides (simple sugars) are glucose and fructose, which together represent about 0.5 percent of flour. They are directly assimilated when the yeast penetrates the membrane of the cell. Simple sugars are transformed into alcohol and carbon dioxide by zymase, the naturally present enzyme contained in the yeast cells. Easy absorption causes these sugars to be used first, during the first 30 minutes of the fermen-tation process.
Complex Glucides (Carbohydrates)
Saccharose and maltose, the two main complex glucides, represent approximately 1 percent of the flour. Because of their complex composition, they spend the first 30 minutes of fermentation undergoing enzymatic transformation into simple sugars that are used later in the fermentation process. Saccharose is transformed into glucose and fructose by the saccharase enzyme, and maltose is transformed into glucose by the maltase enzyme. Both of these enzymes are naturally present in the flour and yeast cells. The glucose and fructose produced is then transformed in carbon dioxide and alcohol by the zymase enzyme that occurs in the yeast cell.
Very Complex Glucides (Carbohydrates)
The main complex glucide is starch, which represents about 70 percent of the flour. Two types are found: amylose and amylopectin. Amylose is degraded into maltose by the beta amylase enzyme, and the maltose is then degraded into glucose by the maltase enzyme. The amylopectin is degraded into dextrin by the alpha amylase enzyme, and the dextrin is degraded into maltose by beta amylase. The resulting maltose is then degraded into glucose by the maltase. Finally, the yeast uses the glucose to generate carbon dioxide and alcohol.
Most of the starch used during fermentation was damaged during the milling process. These damaged particles easily absorb water during dough elaboration, which in turn triggers the enzymatic activity. A non damaged particle of starch will only retain water at its periphery, and not inside the particle itself.
IMPORTANCE OF ENZYMATIC BALANCE IN THE FLOUR
Even though alpha and beta amylase enzymes are naturally present in the flour, the amount of alpha amylase can vary, depending on the germination or sprouting stage of the wheat. When the wheat is preparing to start a new cycle of life (sprouting), the germ sends enzymes to the endosperm, the nutritive tissue of the seed. These enzymes transform the complex components of the endosperm in smaller nutrients that the germ can use.
Typically, flour lacks the alpha amylase enzymes, due to storage quality issues that require harvesting before wheat sprouts. To simplify work for the baker and to keep fermentation as regular and consistent as possible, millers compensate for this lack of enzymes by adding malted flour or fungal enzymes.
Only a minimum amount of starch is used during the fermentation process. Technically, fermentation can last a very long time, but dough does have limits for gas retention. For this reason, it is important for the baker to understand and control fermentation activity.
EFFECTS OF FERMENTATION ACTIVITY ON DOUGH
The most visible effect of fermentation activity is rising due to carbon dioxide production. In the beginning, the gas is dispersed in free water (not fixed by the flour). As the water becomes saturated with gas, an increasing accumulation creates internal pressure that stretches the gluten structure of the dough. Because of its physical properties of extensibility and elasticity, the gluten is able to hold the structure of the dough and retain the carbon dioxide needed to accomplish a good rise.
The second effect of fermentation is the acidification of dough, the production of organic acids that lower its pH. Dough acidification provides an indication of good fermentation activity, and measuring it is a good way to ensure consistent fermentation on a daily basis (pH meters remain the best tool to measure dough acidification). Another very important aspect of acidity is that it delays the staling process and increases product shelf life.
The final important effect of fermentation is the production of aroma. Some aromas are created by alcohol production, others are obtained from organic acids, and still others are created by the secondary reactions that take place during fermentation. Aroma formation takes time, a fact that is especially true during the secondary stage of fermentation. For example, bacteria and different types of "wild" yeast naturally present in the flour generate the aromas related to secondary reactions. This explains why a long fermentation time at the beginning of the baking process is necessary to obtain bread with a good complexity of flavor.
Independent of the physical changes that take place during handling, fermentation changes dough characteristics. During the long first (or bulk) fermentation, the dough develops and strengthens, producing reduced extensibility and increased elasticity.
Because the concepts of extensibility, elasticity, and strength are extensively discussed in this chapter, we need to have a clear understanding at the outset of how these terms are used. Extensibility refers to the stretching property of dough, with easy-to-stretch dough commonly described as having good extensibility. Elasticity refers to the dough's ability to return to its initial position after stretching. Strength refers to the balance between extensibility, elasticity, and a third property called tenacity.
FACTORS AFFECTING FERMENTATION
Different factors will affect fermentation during the baking process, including the amount of yeast, salt, and sugar used; the temperature; and the pH. The baker must control each of these to achieve predictable, consistent results.
Amount of Yeast
The rate of fermentation is directly related to the amount of yeast used in the dough. Specifically, the quantity of yeast must be limited to control fermentation and allow the dough enough time to benefit. Depending on the product and baking process, it should be in the range of 0.5 to 2 percent (fresh compressed yeast) based on the flour for lean dough. A higher amount is necessary for sweet dough.
Yeast activity is faster at higher temperatures and slower at lower ones. To obtain the optimum production of gas and acidity, dough must be kept at approximately 76[degrees]F (24[degrees]C). If it is too warm, gas production will increase, but aroma production will suffer.
Amount of Salt and Sugar
Salt slows down fermentation activity. In general, the amount of salt for a regular and consistent fermentation is 2 percent, based on the total flour in the formula. A small amount of sugar (5 percent) will increase fermentation activity due to higher amounts of nutrients for the yeast. A larger amount (12 percent) will have the opposite effect, slowing fermentation due to a change in yeast cell function.
Commercial yeast works best when the pH of the dough is in between 4 and 6. One of the effects of lower pH is a reduction in fermentation activity that changes the characteristics of the dough. "Wild" yeast and bacteria are better adapted to lower pH, which is why they work so well in these conditions present in the sourdough process.
RELATIONSHIP BETWEEN FERMENTATION AND DOUGH HANDLING
The baking process will determine most of the final characteristics of bread, including flavor, crumb texture, volume, and shelf life. The baking process is best described as a succession of steps that include the handling of the dough (such as mixing, dividing, shaping, scoring, and baking) and its fermentation.
The baking process is so interesting because all these steps are interconnected; technically, it's not possible to isolate any of them. Any change in dough characteristics during one step will, for better or worse, affect all subsequent steps of the baking process.
Relationship Between First Fermentation and Mixing
A long first fermentation considerably increases dough strength and brings several benefits to bread, the two most significant being increased flavor and shelf life.
The process begins during mixing. At this stage, water creates cohesion in all the flour components, creating gluten. The hook of the mixer gives structure to the gluten by stretching its strands and folding them over onto themselves. The more the dough is mixed, the more the gluten structure will be organized, and the stronger the dough will be. This effect continues until the structure of the gluten reaches the overmixed stage, at which point the strands begin to tear.
If the baker opts to increase strength through a long fermentation, it is necessary to decrease mixing time. The longer the first fermentation lasts, the more the structure of the dough is reinforced by the production of acidity. Limiting the mixing time in this case will avoid a double increase in strength that will negatively impact the dough during the subsequent steps of the baking process.
A shorter mixing time also reduces the negative effects of oxidation that occur when oxygen is incorporated into the dough during the mixing process. A small amount of oxygen is necessary to reinforce the binding of the gluten strains, but too much has a negative effect on the components of the flour that are responsible for flavor and crumb color.
It is possible to obtain the advantages and characteristics of bread made by hand with a mechanical mixer by adapting the mixing time. To compensate for the underdeveloped gluten structure created by the mechanical mixing of a short mix, the baker should combine a long first fermentation with a folding technique. The two benefits of folding the dough are
* Reorganization of the gluten structure, duplicating the physical action of the hook during the mixing process
* Expulsion of the carbon dioxide accumulated in the dough during the first fermentation, which optimizes yeast activity (The physical and chemical transformations of the yeast cell are affected when the environment is saturated in carbon dioxide and alcohol.)
Bakers who couple a long mixing time with a long first fermentation can end up with an excess of dough strength that will hurt extensibility during shaping. It will also result in bread with a cross section that is too round, unopened cuts, and a tight crumb structure, as opposed to a natural opening and irregular hole structure. Conversely, underdeveloped dough requires a longer first fermentation with the help of folding to prevent a flat, unappealing appearance.
Relationship Between First Fermentation and Dividing
The dough is divided after first fermentation is complete. At this point, the strands of gluten have been stretched and are more fragile, and the dough is gassier and more difficult to work with. For these reasons, it is important to avoid damaging the dough during this step.
If dividing is done by hand, the baker should find the desired weight within two or three attempts. Too many small pieces of dough will disorganize the gluten structure and will increase dough strength as a secondary effect. In this case, some extra work is needed to reorganize the gluten during the next step of the process, which is preshaping.
If dividing is done by machine, the baker should opt for one that won't damage or tear the gluten during the process. Dividers that work by sucking action, for example, are typically not suitable for gassy dough due to the gluten tearing and damage that occurs. This damage makes preshaping harder and produces dough with excessive strength. Gassy dough also provides some irregularity in the weight of the loaves because the varying levels of carbon dioxide create different ratios of volume and weight in each piece of dough. Instead, hydraulic dividers or stress-free dividers are more suitable for dough with a long first fermentation time.
Relationship Between Dough Characteristics and Preshaping
If the relationship between mixing and first fermentation is respected, the dough should be well balanced in strength at this point of the baking process. However, some factors can prevent this from happening, including using flour that is too strong or that has poor protein quality or dough that is an inappropriate temperature.
Should the dough have insufficient or excessive strength, corrections can be made during preshaping. If the dough is too extensible, the baker can increase strength by making a tighter preshaping that folds the strands of gluten over onto themselves one more time. If the dough is too strong, it must be handled gently to avoid excessively folding the gluten strands.
Relationship Between Dough Characteristics and Shaping
If dough characteristics are not well balanced at this point in the baking process, shaping is the last opportunity to correct them. Dough lacking strength requires tighter shaping. This can be achieved by tightening or folding the dough a little more if hand shaping or by decreasing the space between the two first rollers of the shaping machine. If the dough is too strong, a light shaping is more suitable. Dough should be handled just enough to provide the final shape and to maintain it during the final proof.
Relationship Between Final Proof and Shaping
Compared to dough that has been hand-shaped, dough that has been shaped by machine will last longer through the final proof. The molder makes dough stronger and expels more gas during flattening. Since the dough is stronger and less-gassy, final proofing takes more time to reach the point where the dough is ready to bake. Hand-shaped dough, with its higher gas content and less tightly organized gluten structure, is ready to bake after a shorter period of time.
Relationship Between Dough Characteristics and Scoring
Scoring must be adapted to fit the dough characteristics at the end of the final proof. If the dough is slightly overproofed, scoring should be shallow to avoid deflation. If it is underproofed, it will benefit from deeper scoring, which creates better expansion during oven spring and provides some compensation for lack of volume.
The method in which scoring is done on the surface of the loaf also changes its appearance. A sausage (transversal) cut or a chevron cut gives the bread a rounded cross section, whereas cuts done parallel to the length of the bread create a flatter cross section. For this reason, weak dough looks better when it is scored with a sausage or chevron cut.
Another form of fermentation widely used in baking is preferment. Preferments provide a simple and inexpensive way to improve bread quality, as well as dough and bread characteristics like strength and aroma
Preferment is a dough or batter that is created from a portion of the total formula's flour, water, yeast (natural or commercial), and sometimes salt. It is prepared prior to mixing the final dough, allowed to ferment for a controlled period of time, and added to the final dough.
Types of Preferments
Depending on the type of product to be baked, production scheduling, and available equipment, bakers can select from a number of different preferments. These include prefermented dough, poolish, sponge, and biga. It is also possible to develop unique preferment formulas and pro cesses that rely on the same basic concepts.
Prefermented Dough Prefermented dough (sometimes referred to as old dough) is a fairly new, uncomplicated method that was originally developed to compensate for the mediocre quality of bread produced by using a short first fermentation. Prefermented dough allows the baker to produce a better-quality product even when the first fermentation must be shortened due to production scheduling or mechanization.
The process is fairly simple: A piece of regular dough (made with white flour, water, yeast, and salt) is allowed to ferment for a period of time before being incorporated back in the final mix. In order for the baker to achieve the greatest benefit from the process, prefermentation should last at least 3 hours and should not exceed 6 hours at room temperature.
For longer periods of time before use, it is preferable to let the dough ferment for 1 to 2 hours at room temperature and then to hold it in the refrigerator until incorporation into the final dough. At 35[degrees]F (2[degrees]C) to 45[degrees]F (7[degrees]C), prefermented dough can be stored up to 48 hours. If using this procedure, the baker should remove the prefermented dough from storage 1 or 2 hours before incorporating it into the final dough. If this is not practical, the water temperature in the final dough should be adjusted to compensate for the colder prefermented dough.
Prefermented dough can also be a piece of dough that is saved from a previous mix. For example, a piece of whole wheat dough can be used as preferment for the next day's whole wheat production. In general, however, bakers prefer to save baguette dough because it contains only the four basic ingredients of any dough (flour, water, yeast, and salt), which provides the versatility needed to be used in any kind of final mix.
The amount of prefermented dough needed for various formulas ranges from 10 to 180 percent, based on the flour of the final mix. In general, 40 to 50 percent is the most commonly used proportion. The most convenient way for the baker to procure the quantity required for the next production is to remove the dough to be used as a preferment just after the first fermentation, and to store it in the refrigerator.
One other alternative for prefermenting dough is to mix it as separate dough the day before, or at least 3 hours prior to incorporation in the final dough. In this case, usually about 20 to 30 percent of the flour from the total formula is used in the preferment. The absorption should be adjusted to obtain a medium consistency (generally 64 to 66 percent). Salt is 2 percent, and yeast is 1 to 1.5 percent (fresh). All percentages are calculated based on the amount of flour in the preferment.
No matter how it is made, prefermented dough can be used in many different products, from Viennoiserie like croissants, brioche, and Danish to many different breads, including baguettes, pan breads, and whole wheat and rye breads. The biggest drawback to this method is the large amount of refrigerated space required for overnight storage.
Poolish Poolish is one of the first preferments ever elaborated with commercial yeast. The name is derived from the Polish bakers who are credited with inventing this preferment in Poland at the end of the 19th century. The process was then adapted in Austria and later brought to France by some Viennese bakers. Bread made with a poolish was lighter in texture and less acidic than the sourdough bread common at the time. This feature, coupled with the availability of commercial yeast, led to a quick rise in its popularity.
Technically, we can consider poolish to be a transition between baking with sourdough and baking with commercial yeast using a straight process. Even today, in the windows of some older Paris bakeries, you will find two signs. One will say, "Pain Viennois," or bread from Vienna made with commercial yeast, and the other will say, "Pain Francais," or bread from France made with sourdough. Poolish can be used in many different bread or sweet products, and it is generally the preferment of choice for baguette dough.
Traditionally, the size of a poolish has been calculated based on the water involved in the total formula. Bakers use from 20 to 80 percent of the water to prepare a poolish, which is elaborated using the same amount of flour as water. This creates a hydration of 100 percent and provides a liquid consistency. Poolish does not usually contain salt. It is important to note that poolish is allowed to ferment at room temperature; therefore, the quantity of yeast is calculated depending on the fermentation time. Despite the fact that it is difficult to give precise numbers, Figure 4-3 provides some guidelines to calculate the quantity of yeast required.
Figure 4-3 Yeast Quantity Calculation for Poolish 7 to 8 12 to 15 Fermentation time 3 hours hours hours Quantity of yeast (fresh) * 1.50% 0.70% 0.10% * Based on the amount of flour used in the poolish.
These guidelines are applicable for a bakery temperature of 80[degrees]F (27[degrees]C) to 85[degrees]F (29[degrees]C) and a water temperature of 60[degrees]F (16[degrees]C). If the of the bakery is warmer, the yeast quantity or the water temperature should be decreased. The goal is for the baker to obtain a poolish that is perfectly matured at the time of mixing the final dough. Full maturation is indicated when the poolish has domed slightly on top and has just begun to recede, which creates some areas on the surface that are a bit more concave. A poolish that has not matured adequately does not provide the full benefit of the acidity. One that has overmatured can create other types of acidity that can negatively affect the flavor of the final product. (See Figure 4-4.)
If production and storage are adequate, it is better for the baker to opt for an overnight poolish. This produces more favorable aromas and requires less yeast, increasing the amount of time for use to up to 2 1/2 hours without overmaturing.
Tip: If large amounts of poolish are required for various doughs, it is much easier to divide it into separate containers for each final dough right after it is mixed, instead of measuring after it matures.
Sponge Originally, sponge was used as preferment in pan bread production in England. Today, the sponge process for pan bread production has largely been replaced by the straight dough method, with dough conditioners replacing the sponge. Sponges were also, and still are, used in the production of sweet dough in other European countries as well as the United States.
The sponge process is similar to the poolish process; it differs primarily in dough hydration. While poolish has a liquid consistency, the absorption of sponge is around 60 to 63 percent, creating a stiffer consistency that makes the dough easier to handle. Like poolish, the sponge usually does not contain salt, and the quantity of yeast is calculated depending on the length of the fermentation. In fact, the yeast guidelines for a poolish can be applied to the sponge process. When it comes to taste, sponges and poolish generate very similar aromas; however, it tastes slightly sweeter than the poolish.
A sponge should be used after it has reached full maturation. Its surface contains vital clues to help the baker determine its readiness, including numerous bubbles and the formation of cracks that create some collapse. At this point, the sponge is ready for incorporation into the final dough. An undermature sponge will not be as beneficial because of inadequate acid development, whereas an overmature sponge will have too much, negatively affecting the strength of the dough and the flavor of the bread. (See Figure 4-5.)
A sponge that uses minimal yeast and ferments overnight offers the baker a longer period of time between undermaturation and overmaturation. This longer fermentation time generates enough acidity to ensure good flavor and a longer shelf life.
A sponge can be used in many products. Sweet dough will get the most benefit from the sponge method because the stiffer consistency of the sponge improves the strength of the dough. This increase in strength is usually enough to compensate for the potential weakening of the gluten that is created by the sugar and fat frequently found in sweet bread formulas.
Biga Many Italian bread formulas are made with biga. A close study of these formulas shows that even if the basic ingredients of a biga are the same, the finished preferment can have very different characteristics. Some biga are liquid, some are stiff, some are sour, some are fermented at room temperature, and still others are fermented in a cold environment.
[FIGURE 4-5 OMITTED]
After research (including conversations with Italian bakers), the conclusion can be made that biga is more a generic term for preferment than a reference to a specific process. In the United States, the term is occasionally used instead of "prefermented dough," "poolish," or "sponge" to add a touch of "Italian authenticity" to the bread. Like the preceding preferments, its advantages are good flavor and extended shelf life.
Originally, biga was a very stiff preferment used to reinforce the weaker strength of dough that was, by then, elaborated with weaker wheat. A traditional biga is prepared using flour, water, and yeast, with a hydration of approximately 50 to 55 percent. Unlike the poolish and sponge processes, the quantity of yeast, fermentation temperature, and fermentation time are constant, with 0.8 to 1 percent of fresh commercial yeast typically used. Biga is held at approximately 60[degrees]F (16[degrees]C) for about 18 hours.
True biga can be used for products that require stronger dough characteristics, such as brioche or stollen. It is also a good choice for dough with high hydration. Because of its higher level of yeast, very stiff consistency, and cooler, longer fermentation time, biga naturally develops a superior amount of acidity. Therefore, bakers should use biga properly when also using stronger flour to avoid penalizing extensibility. If extensibility is compromised, higher hydration or autolyse will help regain a better balance.
Advantages and Drawbacks of Preferments
By reviewing the advantages and drawbacks of preferments, bakers should learn how to take full advantage of each method and decide which preferment will work best with a specific flour or dough. Even with the downsides, preferments are worthwhile for bakers, especially when the increased quality of the final product is taken into consideration.
Advantages The main advantage of preferment is to bring all of the benefits of fermentation to the final dough, including gas, alcohol, and acidity.
* Gas production: At this stage of the baking process, gas does not have the same importance as it does after the final dough is mixed because preferments are used to make the final dough, not the final product.
* Alcohol production: During preferment, alcohol reacts with other substances to generate esters, the aromatic components of bread that are very important in producing the flavor of the final product.
* Acid production: At this stage, acidity plays a more important role than gas or alcohol. Its three main effects on the dough and final product are tightening protein to strengthen the dough, lowering the pH triggering an increase in shelf life of the bread by delaying the staling process, and inhibiting mold growth. Finally, as a result of secondary fermentation, organic acids are formed, producing aromas in the dough. Those aromas are very important for the flavor of the final product.
There are two other advantages worth mentioning. First, when the quality of the flour is not optimal, preferment can be a great help in strengthening the dough and compensating for flour deficiencies. Second, preferments facilitate better organization of work. By experimenting with the quantity of preferment involved in the formula, bakers can increase or decrease the length of the first fermentation without jeopardizing the quality of the final product. For example, a longer first fermentation requires less preferment, while the shorter first fermentation, which is more common in bakeries, requires more.
Drawbacks The main drawback to using preferment is the additional work required before final dough mixing. In order to prepare the preferment, additional mixing and scaling are required, either the day before or at least 3 hours prior to mixing the final dough.
Another drawback is the amount of extra space at ideal conditions (room temperature or sometimes refrigerated) necessary to allow prefermentation to happen. For heavy production, this shortcoming can present a significant problem, especially if the production area is small or refrigeration space is limited. In designing a new bakery, it is a good idea to plan a room reserved specifically for preferment. To keep the fermentation activity as consistent as possible, an additional temperature control system can be beneficial.
A final drawback is the potential inability to plan the exact amount of preferment needed relative to the quantity of production. One way to bypass this obstacle is to require customers to place orders at least a day in advance.
The main factors to consider when opting for a specific type of preferment are production and space requirements, flour characteristics, and flavor. Within these parameters, the baker should be able to decide what kind of preferment is best for production. Once the choice is made, it is best to limit the type of preferment to two or three kinds.
In order to obtain the full benefits from using preferments, the baker must understand and respect certain precise technical points in the process. These include mixing the preferment and incorporating it into the final dough.
Mixing Preferments A very basic but extremely important step in mixing is the precise scaling of all the ingredients. This is critical for regulating fermentation activity and ensuring consistency in the final product.
Water temperature should be at approximately 60[degrees]F (16[degrees]C), but it can be adjusted if the baker wants to increase or decrease prefermentation time. Water that is too cold can have a negative effect on the work of the yeast, making it necessary to decrease the quantity of yeast when a longer prefermentation is necessary.
Because gas retention is not important, the gluten structure does not need to be developed. Mixing time should be long enough to fully incorporate the ingredients but short enough to avoid overoxidizing the dough. Depending on the size of the batch, a spiral mixer can complete mixing at first speed in 5 to 8 minutes. For slower mixers, like an oblique or vertical mixer, 2 to 3 minutes at second speed can be added to the mixing time after incorporation to ensure complete incorporation of ingredients.
For liquid preferments, a paddle attachment is preferable to achieve a perfect blend in a shorter period of time. When making a poolish overnight (using a very small amount of yeast), dilute the yeast in water first to diffuse it completely.
Incorporating Preferments Into the Final Dough Timing and quantity must be considered when adding preferment to the final dough.
Preferments are generally added to the final dough at the beginning or during the incorporation period of the mixing process. However, it is sometimes preferable to delay incorporating preferments, as is the case with prefermented dough from a prior, fully mixed batch. This must be incorporated toward the end of the mixing time to avoid double-mixing.
When making dough using autolyse, the preferment should be added to the final dough, along with yeast and salt, only after the autolyse resting period. This is done to avoid any incorporation of yeast into the autolyse. (As discussed in Chapter 3, liquid preferments are added to the dough before the autolyse because their high water content are part of the total dough hydration.) Because of slower fermentation activity, sourdough is a possible exception to this rule. Levain can be incorporated before the autolyse starts; however, if the water temperature is very cold, it is better to incorporate the levain (sourdough culture matured enough to be used to ferment the final dough) after autolyse to avoid delaying the culture's fermentation process.
The quantity of preferment the baker can include in formulas depends on the baking process. A number of factors, such as the strength of the flour, hydration, and the type of preferment help determine the final amount. As a general rule, any time the first fermentation is shorter, the quantity of preferment should be increased to avoid penalizing the quality of the final product. There are, of course, certain limits. For example, if an excessive amount of preferment is added, the acidity level in the dough may be too high. It is possible to determine the optimal percentage of preferment through a series of baking tests. Also, practical considerations like floor space and/or production requirements must sometimes play a part in the decision.
Note: Preferment can also be used to alter water temperature. For example, prefermented dough coming from the cooler is a good substitute for ice or cold water for regulating dough temperature. On the other hand, when using a high-quantity of poolish that has been allowed to ferment at room temperature, the water temperature in the final dough should be decreased. (In certain circumstances, at least half the water used for the poolish is already at room temperature.)
Secondary Effects of Preferment
When flour and water are incorporated, enzyme activity begins. Some enzymes generate sugar degradation (amylase), while others provoke protein degradation (protease).
During prefermentation, the yeast uses up most of the flour's simple sugars, especially during a long fermentation time at room temperature. When this portion of flour is added back into the final dough, the overall quantity of fermentable sugar is lower than what is usually available for the yeast in a straight dough method. As a result, satisfactory crust coloration is difficult to obtain. This defect is sometimes noticeable when a high percentage of overnight poolish or sponge is used in the final dough, or when the enzyme activity of the flour is on the low side. To troubleshoot this problem, 0.5 to 1 percent of diastatic malt (based on the total flour) can be added to the final dough.
Preferments like poolish or sponge sometimes generate low levels of fermentable sugars, which are available at the end of the prefermentation time. In certain cases, these sugars can be used to the baker's advantage. A higher quantity of preferment should be added to the final dough when working with a high level of enzyme in the flour (low falling number). By increasing the percentage of preferment, the portion of the flour with less sugar available to the yeast also increases. This reduces both the fermentation activity and the reddish crust color that is usually obtained when too many enzymes are present in the flour.
Because of their consistency, liquid preferments like poolish favor amylase and protease activity. As a result, the final dough is more extensible. The same protease effect also happens in preferments like sponge that do not have salt and ferment for a long time at room temperature, as opposed to cooler temperatures, which inhibit enzyme activity. The absence of salt in the preparation also encourages a higher rate of protease activity because protease is very salt-sensitive. Cold doughs with salt do not generate the same level of enzyme activity, it is more useful to apply an autolyse process when using prefermented dough than when using a poolish or levain. In addition, flour with a tendency to generate strong dough will give better baking performance when used with a poolish.
An excess of enzyme activity can cause the inside of the preferment to liquefy, especially at the end of the maturation stage, which can compromise the characteristics of the final dough. To correct this problem, add 0.1 to 0.2 percent salt during the preparation of the preferment. The addition of salt can also slow down preferment activity and reduce the risk of overmaturation in hot climates or during summer months.
When it comes to flavor, each preferment generates different aromas depending on its characteristics. Consistency, temperature, salt content, and type of yeast all have some effect on the types of aromas produced and the final flavor of the product. Although it is difficult to describe all the flavors of each preferment, poolish is generally described as having a nutty flavor, sponge is sweeter with more acidity, and prefermented dough is a little bit more acetic without being sour.
Some historians claim that sourdough bread originated in Egypt somewhere between 4000 and 3000 BCE. Legend says that while preparing the unleavened bread of the time, a woman forgot a piece of dough and left it out in the warm, humid Nile River countryside. When she later discovered her mistake, the dough had greatly expanded. She incorporated it into a new batch of dough and baked it. As a result of the mistake, the sourdough process was discovered. For a very long period of time, this method of baking mystified most bakers. However, with the recent evolution of baking science, and microbiology in particular, this natural fermentation process is becoming better understood.
General Sourdough Process
The general sourdough process involves starting a culture of microorganisms (mainly yeast and bacteria), cultivating them to increase their quantity, and using them to ferment the final dough. After this last step, the baker perpetuates some of the reserved culture (the growing of microorganisms in controlled conditions) by adding more flour and water to maintain its activity. (See Figure 4-6.)
[FIGURE 4-6 OMITTED]
Microorganisms Involved in the Sourdough Process
Yeast and bacteria are the two main types of microorganisms that make up the flora present in the sourdough process. Because every microorganism needs a specific environment with favorable conditions for reproduction, the type and quantity of each will be affected by the characteristics of the sourdough, including hydration, ingredients, temperature, acidity, and more.
Both of these microorganisms can be found everywhere: in air, water, on the equipment-even on the baker! The largest source is the flour itself, where one gram contains a total of about 13,000 cells of wild yeast and approximately 320 cells of lactic bacteria.
Yeast Yeast transforms simple sugars like glucose and fructose into alcohol (ethanol) and gas (carbon dioxide) during the fermentation process. Yeast is classified as "wild" because it is present in any natural environment. Most wild yeast cells are members of the Saccharomyces cerevisiae family, the same as commercial yeast, but their genetic characteristics are slightly different. Other species of wild yeast, such as Saccharomyces exiguus, Candida tropicalis, and Hansenula anomala have also been identified. Generally speaking, wild yeast is more resistant to acidity compared to commercial yeast, making it better adapted to the sourdough process.
Bacteria Lactic bacteria are part of the "bacillus" family (Lactobacillus) or "coque" family (Lactocoque) and are divided in two types: homofermentative and heterofermentative. Each has different morphology and a different reaction in the dough. Lactic bacteria also work on certain sugars, converting them into organic acids that are transformed into aromas. Two main types of acid are lactic and acetic. Lactic acid plays a direct role in bread flavor, whereas acetic acid seems to reinforce the flavor provided by the other aromas and accentuates the acid flavor of the final product with a much sharper flavor.
[FIGURE 4-7 OMITTED]
Homofermentative bacteria produce only lactic acid; heterofermentative bacteria produce lactic acid, acetic acid, and carbon dioxide. (See Figure 4-7.)
Starting the Culture
There are many ways to start a sourdough culture, but the principle is always the same. The initial microorganisms come from the flora naturally contained in the flour. To start a successful sourdough process, the baker develops this flora and activates it enough to ferment the final dough. All necessary environmental conditions have to be respected for this to happen.
Microorganisms need three things to reproduce and generate the proper transformations: food, which is provided by the simple sugars naturally contained in flour or from enzymatic activity; water, which is added to the flour; and oxygen, which is supplied by air that is naturally incorporated during mixing.
Organic flour can increase the chance of starting a successful culture. Because it lacks chemical herbicides and pesticides, it is richer in microorganisms. Rye flour is another alternative. By nature, rye flour contains more wild yeast and bacteria than wheat flour and is richer in minerals, another source of nutrients that jump-starts culture activity. Diastatic malt, which is very rich in simple sugars, can also be added to the culture to increase the nutrients available to feed the microorganisms. (See Figure 4-8.)
During the first step of culture elaboration, flour and water are mixed, and oxygen is incorporated to start the microorganisms' activity. At this stage, many different types of microorganisms are present in the culture.
At the beginning, sufficient oxygen in the dough and limited flora create conditions for aerobic activity favorable to the reproduction of microorganisms. After several hours, an increase in the flora starts to reduce the amount of available oxygen, and the microorganisms switch to an anaerobic way of life. Fermentation activity begins, enhanced by a constant, relatively warm temperature. After about 22 hours, the culture has risen to twice its original volume.
During elaboration, a natural balance (quantity and quality) of yeast and bacteria occurs. The selection is made based on the fact that some microorganisms are more or less resistant to the lack of food, lack of oxygen, or acidification of the culture. Cohabitation of the yeast and bacteria is also possible because they are not competing for the same type of nutrients.
Figure 4-8 Starting the Starter Schedule Flour Water Day One a.m. 1 1 lb 1.5 oz (0.500 kg) 2.2 lb whole wheat flour (1.000 kg) 1 lb 1.5 oz (0.500 kg) bread flour Day Two a.m. 1 lb 1.5 oz (0.500 kg) 1 lb 1.5 oz bread flour (0.500 kg) Day Two p.m. 1 lb 1.5 oz (0.500 kg) 1 lb 1.5 oz bread flour (0.500 kg) Day Three a.m. 1 lb 1.5 oz (0.500 kg) 1 lb 1.5 oz bread flour (0.500 kg) Day Three p.m. 1 lb 1.5 oz (0.500 kg) 1 lb 1.5 oz bread flour (0.500 kg) Day Four a.m. 1 lb 1.5 oz (0.500 kg) 1 lb 1.5 oz bread flour (0.500 kg) Day Four p.m. 1 lb 1.5 oz (0.500 kg) 1 lb 1.5 oz bread flour (0.500 kg) Day Five a.m. 1 lb 1.5 oz (0.500 kg) bread flour Day Five p.m. 1 lb 1.5 oz (0.500 kg) 1 lb 1.5 oz bread flour (0.500 kg) Time Before Schedule Starter Next Feeding Day One a.m. 1 -- 24 hours Day Two a.m. 1 lb 1.5 oz (0.500 kg) 6-8 hours Day Two p.m. 1 lb 1.5 oz (0.500 kg) 16 hours Day Three a.m. 1 lb 1.5 oz (0.500 kg) 6-8 hours Day Three p.m. 1 lb 1.5 oz (0.500 kg) 16 hours Day Four a.m. 1 lb 1.5 oz (0.500 kg) 6-8 hours Day Four p.m. 1 lb 1.5 oz (0.500 kg) 16 hours Day Five a.m. 1 lb 1.5 oz (0.500 kg) 6-8 hours Day Five p.m. 1 lb 1.5 oz (0.500 kg) 16 hours (1) Add 1?2 oz (0.015 kg) of malt to the first feeding to help initiate fermentation. This schedule is a guide for starting a starter from scratch. During this process, the starter should be held at 80[degrees]F (27[degrees]C) to encourage fermentation. A mature culture will be able to multiply three times in volume in 8 to 10 hours.
Studies have shown that due to this natural selection, the flora of some levains constituted with the same types of yeast and bacteria differ in element quantity, depending on the conditions of the culture preparation. Other minor populations of wild yeast and bacteria specific to a particular place or a particular process can also be found. This is why, even if the main types of bacteria are the same, each levain is different and will produce breads with different appearance and flavor.
To keep the flora alive and active, it is necessary to ensure that its vital conditions (food/sugar from the flour/water/air) are renewed. This process, completed several times during elaboration, is called feeding the culture. A helpful indication of when the culture needs to be fed is when the surface starts to become concave, or collapsed, in the center.
The time between two feedings depends on the characteristics of the culture, including temperature, activity, hydration, and ingredients. A well-established culture in terms of fermentation activity and acid production should rise to four times its initial volume in 6 to 8 hours of fermentation at room temperature. When this level of activity is reached, the culture becomes a starter. The name comes from the fact that starter is the culture that will start the sourdough process.
The elaboration of the culture can also be sped up by using ingredients other than flour and water, such as malt, honey, water in which dry fruits have been soaked, milk powder, yogurt, fresh fruits, and grapes. The goal is to add extra nutrients in the form of simple sugars to assist the beginning of the fermentation process, as well as to sometimes host a different flora.
From Starter to Levain
Once the starter has been elaborated, the baker needs to keep its activity lively enough to ensure the fermentation of the final dough. A feeding process where flour and water are added to the starter at certain intervals achieves this goal. (See Figure 4-9.) The proportion of flour and water depends on the activity of the culture, the feeding schedule (once, twice, or three times a day), and the production schedule.
The process in Figure 4-9 involves two feedings per day. The last feeding (second feeding, in this example) is called the levain. Levain is the natural preferment used to ferment the final dough.
Depending on the fermentation time between the two feedings, the ratio of starter or first feeding must be adapted. A longer fermentation at room temperature requires a lower amount of starter or first feeding during the feeding preparation. A shorter fermentation time requires more of the starter.
Perpetuating the Culture
There are two possible methods for obtaining the starter used to perpetuate the culture. In the first method, a piece of final dough removed just before salt is incorporated becomes the first feeding (flour and water have been added during the final dough incorporation). This method has the advantage of eliminating one feeding, but there is a risk of changing the culture characteristics because final dough ingredients and temperature are generally different from the ones used to feed the culture. (See Figure 4-10.)
Figure 4-9 Sourdough Feeding Example Flour 100% Water 50% Starter 50% Total first feeding 200% Fermentation for 12 hours at room temperature [75[degrees]F (24[degrees]C) to 80[degrees]F (27[degrees]C)] Flour 100% Water 50% First feeding 50% Total first feeding 200% Fermentation for 12 hours at room temperature [75[degrees]F (24[degrees]C) to 80[degrees]F (27[degrees]C)] and final dough preparation.
[FIGURE 4-10 OMITTED]
In the second method, the starter is removed from the levain just before the levain is incorporated into the final dough. This process has the advantage of keeping the starter purer because it will never be in contact with the final dough. However, it does require an extra feeding. (See Figure 4-11.)
Factors Affecting Culture Characteristics
Several factors can change the microbiological activity of the culture during the feeding process and affect the final characteristics of the bread. Figure 4-12 summarizes the main factors that can affect the sourdough culture and will help the baker to better visualize all these important considerations.
Hydration A stiff culture will have the tendency to develop more acetic acidity, whereas liquid levain will increase the production of lactic acidity.
Temperature High temperatures [85[degrees]F (29[degrees]C) to 90[degrees]F (32[degrees]C)] favor bacterial activity and the production of lactic acidity, but fermentation is more difficult to control due to a higher yeast activity. Low temperatures favor the production of acetic acid and suppress fermentation activity. Temperatures around 77[degrees]F (25[degrees]C) seem to optimize fermentation activity, the development of the dough, and the production of aromas. Yeast activity also favors lactic acid production.
[FIGURE 4-11 OMITTED]
Flour Enzyme activity and bran content determine the amount of simple sugar and minerals available for the microorganism. In general, flour with a higher extraction provides better activity and higher acid production. San Francisco sourdough culture is also generally elaborated with high gluten flour to offset the high level of acidity that will negatively degrade the gluten structure of the dough after long fermentation time.
Salt A small amount of salt (0.1 percent) can be beneficial for a culture with high protease activity, whereas amounts higher than 0.1 percent can inhibit the activity of some microorganisms.
Maintaining the Culture
Maintaining the correct proportion of ingredients, feeding schedule, water temperature, fermentation temperature, and fermentation time are critical for a consistent and healthy culture. To keep the levain in its purest condition, the baker must also pay strict attention to sanitation. Tables and mixers must be cleaned during the feeding process and the mixing of the final dough, taking care to remove scraps of dry dough made with commercial yeast to avoid "contaminating" the culture.
Figure 4-12 Important Sourdough Considerations Final Dough Ingredients Cultural Elaboration Elaboration Flour Hydration Hydration High extraction has Liquid levain Higher hydration a positive effect on increases the increases the volume gas production, but production of lactic of the bread and the a negative effect on acid (positive microbiological the volume of the effect on the volume activity. bread. of the bread, and makes bread less acidic). Stiff levain increases the production of acetic acid. The Enzyme Activity Temperature Temperature Determines the Low temperature At the end of the nutrients available helps the production mixing, the for the of acetic acid. temperature which microorganism. provides the best development is 77[degrees]F (25[degrees]C) to 78[degrees]F (26[degrees]C). Rye Flour Higher temperature Assists the helps the production microbiological of lactic acid and activity. bacterial activity. Negative effect on Also available for the volume of the the storage of the bread. levain during fermentation time. Salt Levain Activity Fermentation Delays the ferment's Growth of the yeast Long fermentation multiplication. increases lactic time (at least 1 Long activity. hour 30 minutes) is necessary to allow Limits protease the activity to take activity of the place in the dough lactic bacteria. (slower process in comparison with commercial yeast). Oxygenation of Water the Dough High chlorine Factor which helps content will delay aroma production. the sourdough activity. Punch and fold increases aroma production.
Troubleshooting Sourdough Culture
Sourdough culture activity can be affected by several factors, including fermentation activity and acid production. It is important for the baker to immediately correct problems before characteristics have changed too much and bread quality is negatively affected. Figure 4-13 summarizes some of the deficiencies that sourdough culture can take on and how to efficiently correct them.
Use in Final Dough
The quantity of levain used in the final dough depends on its characteristics, as well as the characteristics desired in the final product. A large amount of levain, for example, increases the acidity level (or lowers the pH) of the dough. It is important to keep in mind that there are some limits to the amount of sourdough that can be incorporated into a formula.
Figure 4-13 Main Defects of Sourdough Culture Defects Origin Solutions Lack of acidity * Levain too young * Increase the Lack of strength * Lack of fermentation maturation process Bread not very (length of activity) * Allow to ferment at tasty * Fermentation time higher temperature and too short between two at a higher humidity feedings * Use flour with a * Quantity of higher amount of bran sourdough too small in * Make sure the water the final dough is not too chlorinated * Longer fermentation time (8 to 10 hours, for example) * Increase the amount of levain (50%, for example) Excess of acidity * Dough liquification * Start a new culture Bread with a * Old sourdough * Shorten the sharp flavor * Not enough fermentation time consistency in the between the two feeding schedule feedings and lower the * Fermentation time temperature too long between two * Add a little bit of feedings or at too salt to decrease the high of a temperature. activity * Bacteria activity * Reduce the amount too intense of levain (30%, for * Quantity of levain example) too big in the final dough Lack of * Not enough * Add a small amount development of fermentation activity of commercial yeast the bread (low gas production) (max 2%) * Not enough yeast to * Make final dough a make yeast production little bit warmer and * Excess of acidity a little bit softer which inhibits the * Make dough a little yeast activity (even bit warmer and let the with a large enough levain ferment at a population) higher temperature * Long storage at cold * Keep the sourdough temperature at a temperature * Long storage in the higher than freezer 50[degrees]F (10[degrees]C) * Avoid putting the sourdough in the freezer for a long time Lack of strength * Lack of acidity * Longer first in the levain * Lack of gas fermentation production * More punch and fold * Dough too cold at * Use warmer the end of the mixing temperature * Not enough levain in * Increase the amount the final dough of levain Figure 4-14 Example Formula for First Feeding, Levain, and Final Dough Formula The formula in Figure 4-14 will yield 44 loaves scaled at 1 lb 1.5 oz (500 g) each. First Feeding Baker's % Kilogram Lb & Oz Flour 100 0.85 kg 1 lb 14 oz Water 50 0.65 kg 15 oz Starter 80 0.65 kg 1 lb 7 oz Total first 230 1.95 kg 4 lb 4.6 oz feeding Fermentation for 8 hours at room temperature [75[degrees]F (24[degrees]C) to 80[degrees]F (27[degrees]C)] (1) Levain Baker's % Kilogram Lb & Oz Flour 95 2.32 kg 5 lb 1.8 oz Rye flour (2) 50 0.12 kg 4.2 oz Water 50 1.22 kg 2 lb 11 oz First feeding 80 1.95 kg 4 lb 4.6 oz Total levain (3) 230 5.65 kg 12 lb 7.2 oz Fermentation for 8 hours at room temperature [75[degrees]F (24[degrees]C) to 80[degrees]F (27[degrees]C)] (1) Final Dough Baker's % Kilogram Lb & Oz Flour 100 10 kg 22 lb 6.4 oz Water 70 7 kg 15 lb 6.9 oz Salt (5) 2.66 266 g 9.4 oz Levain 50 5 kg 11 lb 3.2 oz Total dough 222.5 22.25 kg 49 lb 0.8 oz Mix (6) Improved mix First Fermentation 3 hours Dividing 500 g (l lb 1.5 oz) Resting time 30 to 40 minutes Shaping Batards Final proof 5 hours Baking (7) 460[degrees]F (238[degrees]C) for 45 minutes; open the oven door for the last 10 to 15 minutes to allow the crust to dry Notes (1) Fermentation time can change, depending on culture fermentation activity (2) Using a small amount of rye flour in the levain preparation has several small but significant effects on the final product. Because rye flour is higher in minerals, it helps to maintain the activity of the levain. Rye flour contains less protein, with lower protein quality than wheat flour, which helps to keep the structure of the levain from becoming too strong (3) Amount of levain includes the levain needed for the final dough levain from becoming too strong perpetuate the culture (4) Amount of water can change depending on the flour absorption. (5) Salt is 2 percent based on the total flour weight (flour involved in the levain plus flour from the final dough). (6) Incorporate all of the ingredients on first speed for 3 to 4 minutes. Then, switch the mixer to second speed and mix just until the dough starts to get smooth. The goal is to achieve a lightly developed gluten structure. (7) Baking time and temperature will vary depending on the type of oven.
Fermentation is a crucial step in the baking process; it is necessary for a good-tasting and long-lasting product. Equally important, fermentation contributes to certain physical changes in the dough related to mechanical reactions, like carbon dioxide pressure, and chemical reactions, like acid production.
Successful bread baking depends on the ability of the baker to understand and control each step of the sequence. The capacity to feel the dough and anticipate eventual changes or defects is also very important in order to make needed corrections and maintain desired results. Unfortunately, a feeling for the dough cannot be learned in books; it must be assimilated through the everyday experience of working with the dough. This learning experience can be a little frustrating at the beginning, but the pleasure of a good loaf of bread is ample reward for time spent mastering its complexities.
Retarding delays fermentation of the dough at any time during the baking process. This fairly new method of baking has been developed not only to meet customer expectations of fresh bread throughout the day, but also to offer the baker a better quality of life by reducing night work.
Despite its advantages, this technique also includes some drawbacks. Specific equipment, the energy needed to produce the required temperatures, and additional floor space all increase the fabrication cost of the final product. In addition, very precise baking methods including temperature, hydration, and fermentation time require that bakers develop good technical knowledge in order to produce consistently high-quality bread.
Four different factors need to be taken into consideration when delaying the fermentation of dough: temperature, gas production, gas retention, and dough's natural degradation process.
All the methods used in retarding are based on the fact that the ferments used in baking are very sensitive to changes in temperature. Commercial yeast, wild yeast, and bacteria generate optimum fermentation activity when the temperature of the dough is between 74[degrees]F (23[degrees]C) and 80[degrees]F (27[degrees]C). At higher temperatures, these microorganisms increase their activity, and commercial and wild yeasts produce more gas. At lower temperatures, yeast and bacteria slow down their metabolism, and carbon dioxide and acidity production decrease. When the temperature drops to 40[degrees]F (4[degrees]C), yeast and bacteria become dormant and most activity is stopped.
The rate of carbon dioxide production depends on both temperature and quantity of yeast. Depending on the retarding method chosen by the baker, the amount of yeast will have to be adjusted. When dough remains at a low temperature for a long period of time, the metabolism of the yeast cell can be altered, affecting fermentation activity later on in the process.
The freshness and quality of the yeast are very important when long delays at a low temperature are planned. It is interesting to note that some yeast companies offer different types of yeast, depending on the baking process for which it will be used (for example, yeast specifically designed for frozen dough is now available to the baker).
In a sourdough process, gas production will depend on the culture fermentation activity. A culture maintained in a liquid stage at room temperature usually produces more gas, compared to a culture maintained in a stiff stage at lower temperatures. The percentage of levain used in the final dough will also affect carbon dioxide production.
Because gluten is elastic and extensible, it can be stretched when the pressure of the gas produced by the yeast increases, and it will hold its structure until its coagulation during baking. The goal of the retarding process is to delay as long as possible the point where the gluten reaches maximum extensibility and breaks under the pressure of the gas. To be more precise, the length of time needed to delay the dough depends completely on how much gas is produced in the dough before it is placed in the retarder.
This is why, in most cases, a short first fermentation time is necessary to delay the point where the dough reaches its gas retention limit. However, this reduced time slows acid production. For this reason, a larger amount of preferment should be used in the final dough to compensate for the lack of acidity.
Another factor that slows fermentation activity is flour with low starch damage. Enzymes use and transform right away damaged particles of starch, providing simple sugars and therefore increasing the availability of nutrients for the yeast.
To delay gas production at the beginning of the process, before dough is placed at cold temperatures, the temperature after mixing should be kept at approximately 73[degrees]F (23[degrees]C).
Natural Dough Degradation
To understand degradation fully, remember that dough evolves significantly during the baking process. This evolution is mainly due to two types of transformation: physical reactions related to changes in gluten and biochemical reactions related to enzyme activity and fermentation.
Like any living thing, dough deteriorates. This deterioration naturally occurs when flour and water are put in contact at the mixing stage, and it continues as the fermentation progresses. Its intensity is proportional to the length of the fermentation time.
Most dough degradation happens because of the action of protease, the enzyme that breaks down the proteins that are the major components of gluten. As these proteins deteriorate, the dough structure itself degrades. Because protease is naturally present in wheat, flour with slightly-lower-than-normal enzyme activity is preferable for retarding. This delays fermentation at the beginning of the baking process and diminishes the risk of red crust color that can happen when there is a longer period of contact between flour and water. When this enzyme activity is triggered, sugar degradation increases, along with the risk of residual sugars that emphasize caramelization at the end of the baking process.
Note: Low enzyme activity doesn't mean that flour with a noncorrected falling number should be used. Whenever possible, flours with a slightly higher falling number (around 350 to 380 seconds) indicating a slightly lower enzyme level are preferable. (Please refer to Chapter 6 to learn more about falling number.)
Another way to delay degradation is to start with dough that is strong enough to withstand retarding. Flour with good protein quality must be used to obtain a gluten structure with good tolerance to fermentation. When the quality is not sufficient, dough oxidizers like ascorbic acid or a higher percentage of preferment may be necessary to reinforce the gluten. It is important to note that quality and quantity of protein are two different things. For a good retarding process, a higher protein quality is more important than a higher quantity. High levels of protein can produce an excess of elasticity that makes the dough difficult to work with after a long stay at low temperatures.
Some adaptations must also be made during mixing. First, hydration should be slightly lower to decrease the amount of water available to the enzymes, which in turn decreases their activity (particularly protease). Second, stiffer dough will provide a stronger gluten structure. Finally, mixing time must be calculated to sufficiently develop the dough and to obtain a strong and fairly well organized gluten structure. Gluten development between improved mix and intensive mix is required for a long retarding time, and the dough temperature should be cooler than usual [around 73[degrees]F (23[degrees]C)].
As a final consideration, smaller batches of dough that are faster to process ensure that the fermentation doesn't start too soon before the retarding process. Tighter shaping also will increase dough strength.
BASIC RETARDING TECHNIQUES
Three basic techniques can be used to delay dough fermentation: delayed first fermentation, slow final proof, and retarding-proofing process. Depending on the method used, retarding can be done at different stages of the baking process. (See Figures 4-15 and 4-16.)
Delayed First Fermentation
For the delayed first fermentation technique, the dough is mixed using an improved mix process; the amount of fresh yeast is around 1.2 percent. Hydration must be sufficient to obtain a medium-soft consistency in the final dough. To reinforce the structure of the gluten, use of preferment is advised. Dough temperature should be 73[degrees]F (23[degrees]C) at the end of the mixing.
* After mixing, place the dough in containers in the retarder set at 45[degrees]F (7[degrees]C) to 48[degrees]F (9[degrees]C). The retarding time can last from 12 to 18 hours.
* After retarding, take the dough out of the retarder and divide it right away, or wait about 1 hour before scaling.
* Divide and preshape as normal. A longer resting time will be necessary to allow the dough to warm up and restart fermentation.
* Follow these steps with normal shaping and a regular final proof.
* Complete baking at the usual temperature and time.
[FIGURE 4-15 OMITTED]
[FIGURE 4-16 OMITTED]
* At 45[degrees]F (7[degrees]C) to 48[degrees]F (9[degrees]C), the fermentation of the dough is not completely stopped. The gas and acidity production is still happening at a lower rate but for a longer period of time. Quality of the final product is not affected by the retarding time.
* When good quality flour is used, there is no need for dough conditioners such as ascorbic acid, keeping the product labeling cleaner.
* Dough with a high water content like ciabatta can be delayed without problems using this technique.
* Because the dough is retarded in bulk before shaping, no blisters are formed during baking.
* The baker can organize production in such a way to offer customers fresh bread all day long without mixing too many batches of dough.
* The main drawback is the need of retarder with enough capacity to store a large amount of dough.
* The bread cannot be baked immediately after its retarding time. Three to four hours are necessary to divide, shape, proof, and bake the bread.
The final product is not immediately available.
Slow Final Proof
With the slow final proof method, mixing time should be adjusted to obtain a gluten structure between an improved mix and an intensive mix, and dough consistency should be a bit stiffer. The amount of fresh yeast generally used is between 0.8 and 1 percent, but it can be adapted depending on the length of the retarding period (a longer fermentation time calls for a lower percentage of yeast). Preferment is advised in the final dough, and dough temperature should be 73[degrees]F (23[degrees]C).
* After mixing, allow the dough to ferment 20 to 30 minutes and then divide and preshape. Rest for 20 to 30 minutes, and shape as normal.
* Place the shaped pieces of dough in the retarder set at 50[degrees]F (10[degrees]C).
* Retard for 12 to 15 hours. When ready, loaves can be baked right away, directly from the retarder.
* At 50[degrees]F (10[degrees]C), fermentation is not completely stopped, but the yeast produces only a small amount of carbon dioxide. This small production for a long period of time allows the baker to obtain the right quantity of carbon dioxide necessary to bake the dough just after removing it from the retarder.
* Dough can be ready to bake after 12 hours. However, the biggest advantage is that due to the slow carbon dioxide production, dough from the same batch can also be baked after 15 hours.
* The baker can plan production to have fresh bread for breakfast and lunch without mixing too many batches of dough.
* Typically, 15 to 20 ppm of ascorbic acid is necessary to reinforce the gluten structure of the dough.
* The surface of the loaves can become dehydrated. For this reason, it is important to have a good humidifier system.
For this method, mixing time is adjusted to obtain a gluten structure between an improved mix and an intensive mix, and dough consistency should be stiffer. The amount of yeast generally used is between 1.8 and 2 percent. Preferment is definitely advised in the final dough to provide strength and flavor, and dough temperature should be 73[degrees]F (23[degrees]C).
* After mixing, divide and preshape the dough; then allow it to ferment for 20 to 30 minutes. Let it rest for 20 minutes and shape, when possible, more tightly than usual.
* Place the shaped pieces of dough in the retarder set at 38[degrees]F (3[degrees]C) to 40[degrees]F (4[degrees]C). Retard from 12 to 48 hours.
* There are two options for the next step. The first is to remove the dough from the retarder and leave it at room temperature for the final proof. If the retarder is also a proofer-retarder, the second option is to set the clock for an automatic increase in temperature [72[degrees]F (22[degrees]C) to 75[degrees]F (24[degrees]C)] after the retarding time to achieve final proof.
When the second method is used, the baker can bake right away the next day and can obtain fresh bread 1 hour after arriving at the bakery.
* Dough conditioners are necessary to reinforce the strength of the dough, and sometimes to avoid the formation of blisters during baking.
* Large proofer-retarders are necessary if all production is retarded, which increases the fabrication cost of the final product.
* Because air is drier at low temperatures, equipment must be able to provide enough humidity to avoid dehydration of the surface of the loaves, which generally happens at a higher rate.
SOURDOUGH IN THE RETARDING PROCESS
When sourdough is used as a preferment, retarding becomes a bit simpler. The high level of acidity naturally reinforces the dough characteristics, and the gluten can handle a longer fermentation time without too much degradation. Dough conditioners are not typically necessary. Because of the strength attained via the acidity of the sourdough culture, rye and whole wheat flours (which are generally too weak to delay fermentation) can also be used in the retarding process.
Many types of equipment can be used in a retarding process. And, even though a number of equipment suppliers offer different types of retarders or proofer-retarders, the key points of focus should be on temperature, humidity production, and air diffusion.
To ensure humidity in a retarder, water is automatically atomized to keep the atmosphere moist enough to avoid dry skin formation on loaves. When a retarding-proofing process is used, enough humidity must be produced during proofing to rehydrate the surface of the loaves that are typically baked right out of the proofer. Sometimes, the condensation effect from the transition from cold to warmer temperatures is enough to create a necessary thin film of water on the dough.
Retarding bread provides the baker with a good way to organize production more efficiently and can increase quality of life. But these improvements come with a cost. The right choices of ingredients (especially flour), method, and equipment are crucial in order to avoid compromising quality.
For the retarding process to be successful, bakers must possess good knowledge and technical skill. Lack of attention to technical considerations will inevitably lead to lower quality in the final product. But when the process is done correctly, night hours can be substantially cut down, to the great enjoyment of the baker.
Dough strength is a direct result of ingredient selection, mixing, and fermentation. Even though having a clear idea of dough strength is very important, it is one of the properties that is the most difficult to assess. It is virtually impossible to learn how to judge strength by reading a technical book. Only a great deal of practical work with a lot of dough at the bakery will educate the hands to feel (or evaluate) strength and make corrections when necessary.
Many parameters can affect the strength during the entire baking process. The remainder of this chapter covers the main issues in order to help the baker understand what can go wrong and how to fix it.
DEFINITION OF STRENGTH
Strength is a balance among three physical dough characteristics: extensibility, elasticity, and tenacity.
Extensibility is the property of the dough to be stretched. Dough with good extensibility is easy to stretch. This characteristic is fairly important for manual shaping of long products like baguettes, as well as for producing laminated dough.
Elasticity refers to the dough's ability to return to its initial position after being stretched. Dough that will noticeably spring back after being stretched is judged too elastic.
Tenacity is the property that resists a stretching action. This property can influence the elongation part of the shaping process. If the dough puts up a lot of resistance to the baker's efforts to make it longer, it is described as tenacious.
A solid relationship or connection exists between tenacity and elasticity. Elastic dough will naturally resist the stretching action, and dough with a lot of tenacity has the tendency to retract to its initial position very quickly. For this reason, at a bakery level, strength is often described as a balance between extensibility and elasticity. However, in a laboratory environment, the three characteristics are taken into consideration when evaluating flour characteristics, and especially gluten properties.
STRONG DOUGH VERSUS WEAK DOUGH
Elastic dough, extensible dough, strong dough, and weak dough are common terms in the bakery. Quite often, these important descriptions are confused.
Strong dough is precisely defined as dough with a lack of extensibility and an excess of elasticity. For the baker, this translates as dough that is difficult to stretch during hand or machine shaping, along with a tendency to retract once the desired length is achieved. Strong dough results in shorter finished breads with a rounder cross section and inferior cuts openings. These defaults can easily be explained by the lack of gluten extensibility, which penalizes the development of the bread during proofing and/or oven spring.
In contrast, weak dough has so much extensibility that it is easy to stretch, and so little elasticity that it will not spring back during shaping. Despite good machinability, the gluten lacks the strength to retain much gas during the proofing and baking. As a direct result, finished products have a very low volume, a flat cross section, dense crumb structure, and poorly developed cut openings.
FACTORS AFFECTING DOUGH STRENGTH
Dough strength is affected by ingredients, mixing, and fermentation.
Flour Because flour is the main ingredient in dough, it has a huge impact on strength. Flour with a high level of protein will provide more gluten, resulting in dough with high elasticity and low extensibility. Low protein has the opposite effect, and very low protein flour will generate dough with a definite lack of strength.
Protein Quality Flour made with soft wheat, such as pastry flour, doesn't have the same gluten-forming ability compared to flour made with hard wheat, such as bread flour. As a result, bread made with a soft wheat flour leads to dough with poor strength and gas retention. At the same time, different kinds of hard wheat contain varying levels of protein and can create very different dough and bread characteristics. For this reason, it is difficult to provide the exact amount of protein needed, but on average, flour between 10.5 and 12 percent should provide a good balance between extensibility and elasticity.
Ash Content A lot of bran left in the flour after the milling process will interfere with gluten formation and generally lead to dough with less strength. For example, whole wheat flours create dough that is always more extensible, with lower gas retention than doughs made from regular bread flours. Flour with a low ash content like patent flour generates dough with a tendency to develop a little extra strength. Again, it is difficult to give precise ash content, but in general ash content of around 0.5 percent is desirable.
Flour Treatments Some flour treatments, such as oxidizers like ascorbic acid or potassium bromate, automatically generate an increase in strength. The bleaching agent benzoyl peroxide doesn't really affect strength as much as it does the color of the crumb in the finished product. ADA or azodicarbonamide, a maturing agent, also increases dough strength. Malt or fungal amylase has only a secondary effect on strength by promoting enzyme and fermentation activity.
Natural Maturation Natural maturation, which is directly related to the natural oxidation of the flour, has an impact on the strength of the dough. Fresh flour has the tendency to lack strength, while properly matured flour is more balanced. This is why it is always recommended to allow the flour to mature for 2 to 3 weeks before using it in baking.
Water Water quality and quantity can have an effect on dough characteristics. The minerals found in hard and soft water are used as yeast nutrients in a dough system and play an important role during fermentation activity. Hard water, because of its higher mineral content, generates dough with higher fermentation activity and leads to dough with higher strength, compared to dough made with soft water and lower mineral content.
Dough hydration, which is directly related to the amount of water used in the formula, will also affect strength. Underhydrated proteins create gluten that lacks extensibility and has an excess of elasticity. Overhydrated proteins create very extensible dough with a lack of elasticity that requires some changes in the baking process. These can include using a longer mixing time, more folds, or a longer fermentation time.
Other Ingredients Some ingredients, like butter or a high level of sugar (15+ percent), increase dough extensibility. Others, such as seeds or other chunky ingredients like nuts, chocolate chips, or fruit, weaken gluten. In the latter case, certain precautions must be taken to bring the dough back to a good balance, including a longer mixing or more folds. To avoid any damage to the gluten and to preserve structure and strength as much as possible, chunky ingredients should be added at the end of the mixing time after the gluten structure has been properly formed.
Autolyse By using an autolyse process, the baker automatically changes the characteristics of the gluten. By allowing the incorporated flour and water to rest for an average of 20 minutes to 1 hour, the proteins will have more time to absorb water and create better boundaries. This improves the structure of the gluten network. At the same time, the protease will degrade some of the chains of proteins, slightly weakening the gluten structure and creating a positive effect on extensibility. Mixing time can be reduced, since the more extensible gluten will organize faster under the mechanical action of the mixer's hook.
In addition, the working characteristics and machinability of the dough will be improved. Breads will have a better crumb cell structure (more open and creamier due to lower mixing time), a slightly larger volume, and better cut openings due to better expansion during the first stage of baking.
Deactivated Yeast Deactivated yeast can be used to improve dough extensibility without using the autolyse process. Because deactivated yeast is a natural product with a "clean" label, it is increasingly used in laminated dough and formulas of long, shaped bread like baguettes. This type of yeast does not generate any fermentation activity.
Mixing Time Mechanically mixing for longer periods of time stretches and folds gluten strands so that they are longer and more tightly bound, creating a more organized, stronger gluten structure. Shorter mixing times create less binding and generate weaker gluten structure. The baker can compensate for the latter by increasing first fermentation time and using one or several stretches and folds.
Temperature Dough temperature has an indirect impact on strength. Warmer dough generates more fermentation activity and stronger dough, while cooler dough lowers fermentation activity and produces weaker dough.
In its advanced stages, fermentation creates acidity, which is responsible for three important reactions. The first is the creation of aromas through acids like organoleptic acids. The second is the lowering of dough pH that increases the shelf life of the bread. The last reaction, which is more related to strength, is the physical and chemical reinforcement of gluten bonds.
All three reactions occur at the same time. This means that bakers who want to achieve good flavor characteristics through long fermentation will also get stronger dough (sometimes excessively strong). To avoid this, adjustments should be made in the baking process, including shorter mixing time and higher hydration in the formula. For dough made without first fermentation, longer mixing time and sometimes dough oxidizers are needed. This step is necessary to build up enough strength to the dough to compensate for the fact that no acidity will be produced after mixing.
Mass Effect The quantity or "mass" of dough allowed to ferment also plays a role in strength, with a larger piece of dough increasing in strength faster than a smaller one. The chemical reactions happen faster in larger masses of dough, creating a better environment for microorganism activity. This is what we refer to in the baking industry as the "mass effect" Mass effect is particularly important to consider when adapting formulas developed for home baking to a production environment, and vice versa. For smaller batches of dough, up to 61b (2.724 kg), longer fermentation time may be necessary, while larger batches of 50 lb (22.7 kg) and more require slightly shorter fermentation time.
Preferments As a general rule, any time a preferment is added, strength increases. However, other factors concerning preferments must also be taken into consideration, including type, quantity, and the degree of maturation when incorporated.
Types of Preferments Because of the large amount of water involved in their formulas, liquid preferments like poolish develop more enzymatic activity. In this case, protease activity is particularly interesting, as it brings all of the advantages of autolyse. Preferment allowed to ferment at room temperature and without salt (like sponge) also brings some protease activity. If sponges are stiff, less enzyme activity is generated, but the amount is typically sufficient to generate positive effects. When a sourdough process is used, the dough automatically develops more strength due to the higher level of acidity. This increase in strength can retard some of the dough. Due to its consistency, liquid sourdough promotes better dough extensibility and is recommended for the production of long shapes, like sourdough baguettes.
Quantity Used in the Final Dough When using preferments, the increase in strength is proportional to the quantity used. Bakers consider this factor when developing formulas.
The amount of preferment directly relates to the length of first fermentation. When a short first fermentation time exists, a larger amount of preferment can and should be used. If a long first fermentation time is possible, the amount should be lowered. This is a common mistake in some bakeries, where bakers think about preferment solely in terms of flavor.
Preferment can also be used for troubleshooting. For example, flour with a lack of fermentation tolerance or a lack of maturation will benefit from a higher percentage of fermented flour in formulas.
Degree of Maturation Preferments must be properly matured for maximum benefit. Overmatured preferment can lead to excessive strength and, eventually, to acid levels that are so high they cause gluten deterioration. Dough takes longer to mix and starts to break down during the first fermentation, resulting in very low final product quality. When this happens, it is necessary for the baker to decrease the amount of preferment in the final dough and to recalculate percentages to take this into consideration. Undermatured preferment requires a longer first fermentation time to compensate for the lack of acidity.
Dough Handling The way the dough will be handled, whether by hand or with machinery, will also have a direct effect on strength. Tight preshaping and shaping increase elasticity and decrease extensibility, whereas light preshaping and shaping preserve extensibility but hurt elasticity. Bakers must learn how to evaluate the strength of the dough in order to handle it properly. This strength judgment, or evaluation of the feeling of the dough, is probably the most difficult lesson in the baking profession and is best mastered simply by working with dough.
In many bakeries, it is commonly believed that the harder or stronger the dough is worked, the better it is. In fact, if all the appropriate steps have been carefully followed, a gentle preshaping and shaping are all that is needed.
Scoring is also important for the strength of the dough. Cuts perpendicular to the side of the loaves favor an upright expansion of the bread during oven kick and are more suitable for weaker dough like rye or whole wheat. The upright expansion naturally favors the cross section of the bread and, therefore, its volume and final appearance. Cuts parallel to the side of the loaves favor a sideways expansion of the bread. These cuts create great openings that are more suitable for stronger dough like baguettes or sourdough.
It is easy to understand why fermentation is the most important step in baking. The quality of bread is greatly dependent on a number of factors, including duration of fermentation, temperature, hydration, and quantity of yeast among others. The development of aromas and the flavor profile are accomplished with fermentation and its handling.
From straight dough with short or long first fermentation, from yeasted preferments to sourdough, or from baked the same day to delayed overnight, the baker has numerous choices. Regardless of the fermentation process selected, it is important for the baker to have a comprehensive understanding of the biochemical reactions and physical changes that happen in dough during this crucial step. Not only will they be able to produce consistently high-quality bread day after day, but they will also be able to develop many different flavor profiles to accommodate their customers' needs.
* Prefermented dough
* Simple sugars
1. What is fermentation?
2. What are the results of the fermentation activity on the dough and on the bread?
3. What is the relationship between mixing and fermentation?
4. What are the technical factors to take into consideration when using preferments?
5. What are the two main microorganisms involved into a sourdough process?
What are their effects on the dough and on the finished product?
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|Title Annotation:||PART 2 BREAD|
|Publication:||Advanced Bread and Pastry|
|Date:||Jan 1, 2009|
|Previous Article:||Chapter 3 The baking process and dough mixing.|
|Next Article:||Chapter 5 Baking bread.|