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    Feature 3 -  March/April 2004
     

    Pre-ferments  (part one) 

    By Didier Rosada (SFBI)

     

    To the bread baker, an understanding of the fermentation process in yeast-risen baked products is vital. Depending on the conditions under which the dough is mixed and handled, proper fermentation can contribute to many of the desirable characteristics expected in good bread including aroma and shelf life.  The goal of part one of this two-part article is to define and explain more precisely one way of using fermentation to improve bread quality: pre-fermentation and the use of pre-ferments. 

    Even if preferments are commonly used in the industry, there are still a lot of confusion about their functions, applications and the different types. I really believe that all baking educators should have a good understanding of this “practical tool” that future bakers will certainly use in his (or her) production. 

    Definition

    A pre-ferment could be defined as a dough or batter prepared prior to mixing the final dough composed of a portion of the total formula’s water, yeast (natural or commercial), and sometimes salt. The dough is allowed to ferment for a controlled period of time, and then is added to the final dough.

    Depending on the type of product to be baked, the production scheduling, and the equipment available, the baker has a number of options to consider in determining what type of pre-ferment to use. 

    Types of pre-ferments

    Nowadays, there is considerable confusion and misinformation about pre-ferments and their origins.  What is the difference between pre-fermented dough, a poolish, a sponge, and a biga?   

    Pre-fermented dough

    Pre-fermented dough (or old dough) is a very simple and fairly new method.  Originally, this pre-ferment had been developed as a compromise, to compensate for the mediocre quality of bread produced by the straight dough process with a short first fermentation.  Pre-fermented dough allows the baker to produce a better quality product even when, due to production scheduling or mechanization, the first fermentation has to be shortened.

    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 incorporating it back in the final mix.  In order for the baker to get the most benefit from this process, the pre-fermentation should last at least three hours at room temperature.  Pre-fermented dough can ferment up to six hours at room temperature.  For longer periods of time before use, it is preferable to let the dough ferment one or two hours at room temperature and then to hold the pre-ferment refrigerated until its incorporation in the final dough.  The storage of the pre-fermented dough at low temperature (35 - 40°) could last up to 48 hours.  If using this procedure, the baker should remove the pre-fermented dough from storage one or two hours before incorporation into the final dough, or if this is impractical,  adjust the water temperature in the final dough to compensate for the cold pre-ferment.

    Pre-fermented dough could also be a piece of dough saved from a previous mix.  For example, a piece of whole-wheat dough can be used as pre-ferment for the next days whole-wheat production, but in general, bakers prefer to save baguette dough for their pre-fermented dough.  Baguette dough, being composed of only four ingredients, offers more versatility and can be used in any kind of final mix.  The most convenient way for a baker to procure the necessary quantity of pre-fermented dough needed for the next production is to remove the dough to be used as a pre-ferment just after the first fermentation, and to store it in the refrigerator.

    Formulas can call for as little as 10% and as much as 180% pre-fermented dough (based on the flour of the final mix) but 40 – 50% is the most commonly used proportion.

    One other alternative is to mix the dough to be used for the pre-ferment 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% of the flour from the total formula is used in the pre-ferment.  The absorption should be adjusted to obtain a medium consistency (generally 64-66%).  Salt is 2% and yeast 1 to 1.5% (fresh).  These percents are all calculated based on the flour in the pre-ferment. 

    Pre-fermented dough is a very versatile pre-ferment and can be used in many different products, from viennoiseries (croissant, brioche, danish . . .) to many different breads (baguettes, pan breads, whole wheat, rye . . .).  The biggest drawback is overnight storage – a large amount of refrigerated space is required.   

    Poolish

    Poolish is one of the first pre-ferments elaborated with commercial yeast.  Polish bakers, where the name would come from, are credited with inventing this pre-ferment in Poland at the end of the 19th century.  The process then was adapted in Austria and later in France.  The bread made with a poolish was lighter and less acidic than the sourdough bread commonly baked at this time, and started to gain in popularity.  With the availability of commercial yeast, more and more bakers began using the ‘poolish process’ and the ‘sourdough process’ declined.  Technically, we could consider the poolish as a transitional pre-ferment between baking using sourdough, and baking with commercial yeast -- using a straight process.  Even in Paris today, in some windows of older bakeries, you will find two signs.  One reads “pain Viennois” – bread from Vienna (made with commercial yeast), and the other reads “Pain Francais” – bread from France and made with sourdough. 

    Traditionally, the size of the poolish was calculated based on the water involved in the total formula. Bakers could use from 20 to 80% of the water to prepare the poolish. The poolish was then elaborated using the same amount of flour as water (hydration of 100%, providing a liquid consistency); no salt is usually incorporated in the poolish.  It is important to note that the poolish is allowed to ferment at room temperature; therefore, the quantity of yeast is calculated depending on the fermentation time of the poolish.  Despite the fact that it is difficult to give precise numbers, chart A provides some guidelines to calculate the quantity of yeast to use in the poolish: 

    Chart A 

    Fermentation time                   3 hours            7 to 8 hours                 12 to 15 hours

    Quantity of yeast (fresh)*       1.5%                    .7%                                 .1%

    * Based on the flour involved in the poolish 

    These guidelines are applicable for a bakery temperature of 80 to 85°F and a water temperature of 60°F.  If the temperature of the bakery is warmer, the yeast quantity or the water temperature should be decreased.  The goal for the baker is to obtain a poolish that is perfectly matured at the time of the final dough mixing.  The full maturation of the poolish can be recognized when it has domed slightly on the top and just begun to recede, creating on the surface some areas a little more concave.  A poolish that has not matured adequately does not provide the benefit of lower acidity; one that has over-matured can create other types of acidity which might affect the flavor of the final product.

    It is better for the baker to opt for an overnight poolish if production and storage are adequate for two main reasons.   A longer poolish produces more favorable aromas, and a longer poolish requires less yeast, increasing the amount of time to use the poolish (up to 2 ½ hours) without the poolish over-maturing.

    (Tip: if you require large amounts of poolish for various different doughs, it is much easier to divide the poolish into containers for each dough right after the mixing of the poolish, instead of measuring the poolish after its maturation phase.) 

    Poolish can be used in many different bread or sweet products but generally, poolish is the pre-ferment of choice for baguette dough. 


    Poolish properly mature surface close up


    Poolish when ready to mix in final dough


    Poolish after mixing

    Sponge 

    Originally, sponge was used as pre-ferment in pan bread production in England.  Unfortunately, today the sponge process has been replaced by the straight dough method with dough conditioner’s replacing the sponge.  Sponges were, and still are, also used in the production of sweet dough.

    The sponge process is similar to the poolish process; they differ primarily in dough hydration.  While the poolish has a liquid consistency, the absorption of the sponge is around 60 – 63% (stiff dough).  The sponge usually does not contain salt, and the quantity of yeast is calculated depending on the length of the fermentation.  The same yeast guidelines for a poolish (chart A) could be applicable for a sponge process.

    A sponge should also be used after is has reached full maturation.  As with the poolish, the surface of the sponge contains vital clues to help the baker determine its readiness.  When many bubbles are evident and some cracks start to form, creating some collapsing, the sponge is ready for incorporation into the final dough.  An under-mature sponge would not be as beneficial because of inadequate acid development; an over-mature sponge could negatively affect the strength of the dough due to an increase in the acidity level, and would affect the flavor of the bread due to the formation of other acids.

    A sponge using minimal yeast and overnight fermentation offers the baker a longer period of time between under-maturation and over-maturation.  Because of the longer fermentation time generating more acidity, the final product will also get better flavor and longer shelf life.

    The stiffer consistency of the sponge process makes it easier to handle than a poolish.  Taste-wise, sponge and polish generate aromas very similar. 

    A sponge can be used in many products.  Sweet dough in particular will get the most benefit from the sponge method.  Because of its stiffer consistency, the sponge will improve the strength of the dough. This increase in strength is usually enough to compensate for the potential weakening of the gluten generated by the sugar and fat frequently found in sweet bread formulas. 


    Sponge properly mature surface close up


    Sponge when ready to mix in final dough

     


    Sponge after mixing

    Biga

    Many Italian bread formulas start with a ‘biga’ as a pre-ferment. After a close study of many of these formulas it is noticeable that a biga, even if the basic ingredients are the same (flour, water, and yeast), could have different characteristics: liquid or stiff, some are sour, some are fermented at room temperature, while others are fermented in a cold environment.

    After research which included conversations with Italian bakers, the conclusion can be made that biga is more a generic term for pre-ferments than a specific process.  In the United States, occasionally the word biga is used instead of pre-fermented dough, poolish, or sponge to add a touch of ‘Italian authenticity’ to the bread.

    Biga originally was a very stiff pre-ferment used by Italian bakers to reinforce the strength of the dough. A traditional biga is prepared using flour, water, and yeast.  The hydration is around 50-55% (very stiff).  Unlike the poolish and the sponge process, the quantity of yeast, the fermentation temperature, and the fermentation time are constant.  Usually, .8 to 1% of fresh commercial yeast is used.  The biga is then held at around 60°F for about 18 hours.

    Because of the very stiff consistency and the cooler fermentation, biga provides a lot of strength to the dough, which was its original purpose.  Today, with stronger flour, the baker must be careful to use the biga properly, or the added strength could penalize extensibility.  The advantages of a properly fermented biga are similar to other methods: better flavor and extended shelf life. 

    True biga can be used for products requiring stronger dough characteristics such as brioche or stollen.  It is also a good choice in dough with high hydration. If the biga is causing an excess of strength to the dough, higher hydration or autolyse will help regain a better balance in elasticity and extensibility. 

    Pre-fermented dough, poolish, sponge and biga are the primary type of commercial yeast raised pre-ferment available to the baker.  It is possible for a baker to develop a unique pre-ferment (between a sponge and a polish, for example), but the concept stays the same.  The use of pre-ferments is a simple and inexpensive way to improve bread quality; pre-ferments also improve dough characteristics including strength and aroma.

    In order to take advantage of a pre-ferment, the baker must adhere to some basic principles and technical considerations.  This is the topic of part two of this article. 

    To learn more about this topic, further references can be found in “The taste of bread” from Raymond Calvel.


    Didier Rosada, Baking Instructor  

    Didier began his baking career in the traditional way: at age 15, with technical training at a regional French professional school and an apprenticeship under a local baker. But his love of bread and his desire to see the world soon set him apart — and his career on a very untraditional path. 

    After a few stints as staff baker in some exotic places, Didier’s abilities caught the attention of his employer, Club Med. He was assigned to the clubs with the most sophisticated clientele. Then Club Med noticed Didier’s organizational skills, and assigned him the task of opening new or remodeled bakeries at the company's resorts. Included in his responsibilities was training local bakers to work in these bakeries.  In 1995, Didier returned to France to enhance his professional skills at the prestigious Institut National de Boulangerie-Patisserie in Rouen. After five months of highly technical and business oriented training, he was awarded a Brevet de Maitrise, a degree that we would call a “Masters in Baking.” 

    While working on a private research project for Bay States Milling Company in the United States, Didier became unofficial trainer of the 1996 Baking Team USA. His expert advice and patient guidance were important factors in the American team’s first place finish in the bread category at the Coupe du Monde de Boulangerie in Paris in February 1996. In February 1999 under Didier’s guidance the team USA took home the gold medal of the competition and in April 2002, the silver medal. He will be the official coach for the 2005 Baking Team USA. 

    Didier has also contributed many technical articles for newsletters and baking magazines His formulas have been published in the professional press and are considerate by the industry to set the standards of quality in Artisan Baking. 

    When the National Baking Center was created in 1996, Didier was selected to develop and teach the Bread curriculum. His other functions at the NBC included the supervision of various research projects and consulting for specialty bread bakers across the United States, South and Central America, Europe and Asia. 

    Since January 2002, he has been working as Head Instructor for the San Francisco Baking Institute where he continues to specialize in baking education and consulting, nationwide and internationally.
     
     

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