The subject of preferments is one that can cause immense confusion among bakers. The variety of terminology can bewilder even the most experienced among us. Words from foreign languages add their contribution to the complexity.
A preferment is a preparation of a portion of a bread dough that is made several hours or more in advance of mixing the final dough. The preferment can be of a stiff texture, it can be quite loose in texture, or it can simply be a piece of mixed bread dough. Some preferments contain salt, others do not. Some are generated with commercial yeast, some with naturally occurring wild yeasts. After discussing the specific attributes of a number of common preferments, we will list the benefits gained from their use.
- pâte fermentée
- madre bianca
These terms all pertain to preferments; some are quite specific, some broad and general. The important thing to remember is that, just as daffodils, roses, and tulips all are specific plants that fall beneath the heading of “flowers,” in a similar way the above terms all are in the category of “preferments.” Let’s examine several of the terms listed in more detail.
Pâte fermentée, biga, and poolish, are the most common preferments which use commercial yeast. As such, we can place them loosely in a category of their own. We place sourdough and levain in a separate category.
Pâte fermentée is a French term that means fermented dough, or as it is occasionally called, simply old dough. If one were to mix a batch of French bread, and once mixed a portion were removed, and added in to a new batch of dough being mixed the next day, the portion that was removed would be the pâte fermentée. Over the course of several hours or overnight, the removed piece would ferment and ripen, and would bring certain desired qualities to the next day's dough. Being that pâte fermentée is a piece of mixed dough, we note that it therefore contains all the ingredients of finished dough, that is, flour, water, salt, and yeast.
Biga is an Italian term that generically means preferment. It can be quite stiff in texture, or it can be of loose consistency (100% hydration). It is made with flour, water, and a small amount of yeast (the yeast can be as little as 0.1% of the biga flour weight). Once mixed, it is left to ripen for at least several hours, and for as much as 12 to 16 hours. Note that there is no salt in the biga. Unlike pâte fermentée, which is simply a piece of mixed white dough which is removed from a full batch of dough, the biga, lacking salt, is made as a separate step in production.
Poolish is a preferment with Polish origins. It initially was used in pastry production. As its use spread throughout Europe it became common in bread. Today it is used worldwide, from South America to England, from Japan to the United States. It is by definition made with equal weights of flour and water (that is, it is 100% hydration), and a small portion of yeast. Note again the absence of salt. It is appropriate here to discuss the quantity of yeast used. The intention is not to be vague, but it must be kept in mind that the baker will manipulate the quantity of yeast in his or her preferment to suit required production needs. For example, in a bakery with two or three shifts, it might be suitable to make a poolish or any other preferment and allow only 8 hours of ripening. In such a case, a slightly higher percentage of yeast would be indicated in the preferment. On the other hand, in a one-shift shop, the preferment might have 14 to 16 hours of maturing before the mixing of the final dough. In this case the baker would decrease the quantity of yeast used. Similarly, ambient temperature must be considered. A preferment that is ripening in a 65°F room would require more yeast than one in a 75°F room.
sourdough and levain
The words sourdough and levain tend to have the same meaning in the United States, and are often used interchangeably. This however is not the case in Europe. In Germany, the word sourdough (sauerteig) always refers to a culture of rye flour and water. In France, on the other hand, the word “levain” refers to a culture that is entirely or almost entirely made of white flour. While outwardly these two methods are different, there are a number of similarities between sourdough and levain. Most important is that each is a culture of naturally occurring yeasts and bacteria that have the capacity to both leaven and flavor bread. A German-style culture is made using all rye flour and water. A levain culture may begin with a high percentage of rye flour, or with all white flour. In any case, it eventually is maintained with all or almost all white flour. While a rye culture is always of comparatively stiff texture, a levain culture can be of either loose or stiff texture (a range of 50% hydration to 125% hydration). With either method, the principle is the same. The baker mixes a small paste or dough of flour and water, freshens it with new food and water on a consistent schedule, and develops a colony of microörganisms that ferment and multiply. In order to retain the purity of the culture, a small portion of ripe starter is taken off before the mixing of the final dough. This portion is held back, uncontaminated by yeast, salt, or other additions to the final dough, and used to begin the next batch of bread.
One important way in which a sourdough and levain are different from pâte fermentée, biga, and poolish, is that the sourdough and levain can be perpetuated for months, years, decades, and even centuries. When we make a preferment using commercial yeast, it is baked off the next day. We then begin the process again, making a new batch of preferment for the next day’s use. It would be tempting to say the pâte fermentée can be perpetuated, since each day we simply take off a portion of finished dough to use the following day. This is not actually the case. We could not, for example, go on vacation for a week and come back to a healthy pâte fermentée, whereas we could leave our sourdough or levain culture for a week or more, with a minimum of consequences.
During the initial stages in the development of a sourdough or levain culture, it is common to see the addition of grapes, potato water, grated onions, and so on. While these can provide an extra nutritional boost, they are not required for success. The flour should supply the needed nutrients for the growing colony. Keep in mind, however, that when using white flours, unbleached and unbromated flour, such as those produced by King Arthur® Flour, are the appropriate choice. Vital nutrients are lost during the bleaching process, making bleached flour unsuitable.
How does the baker know when his or her preferment has matured sufficiently and is ready to use? There are a number of signs that can guide us. Most important, it should show signs of having risen. If the preferment is dense and seems not to have moved, in all likelihood it has not ripened sufficiently. Poor temperature control, insufficient time allowed for proper maturing, or a starter that has lost its viability can all account for the problem. When the preferment has ripened sufficiently, it should be fully risen and just beginning to recede in the center. This is the best sign that correct development has been attained. It is somewhat harder to detect this quality in a loose preferment such as a poolish. In this case, ripeness is indicated when the surface of the poolish is covered with small fermentation bubbles. Often CO2 bubbles are seen breaking through the surface. There should be a pleasing aroma that has a perceptible tang to it. Take a small taste. If the preferment has ripened properly, we should taste a slight tang, sometimes with a subtle sweetness present as well. The baker should keep in mind that a sluggish and undeveloped preferment, or one that has gone beyond ripeness, will yield bread that lacks luster, and suffers a deficiency in volume and flavor.
There are a number of important benefits to the correct use of preferments, and they all result from the gradual, slow fermentation that is occurring during the maturing of the preferment:
- Dough structure is strengthened. A characteristic of all preferments is the development of acidity as a result of fermentation activity, and this acidity has a strengthening effect on the gluten structure.
- Superior flavor. Breads made with preferments often possess a subtle wheaty aroma, delicate flavor, a pleasing aromatic tang, and a long finish. Organic acids and esters are a natural product of preferments, and they contribute to superior bread flavor.
- Keeping quality improves. There is a relationship between acidity in bread and keeping quality. Up to a point, the lower the pH of a bread, that is, the higher the acidity, the better the keeping quality of the bread. Historically, Europeans, particularly those in rural areas, baked once every two, three, or even four weeks. The only breads that could keep that long were breads with high acidity, that is, levain or sourdough breads.
- Overall production time is reduced. Above all, to attain the best bread we must give sufficient time for its development. Bread that is mixed and two or three hours later is baked will always lack character when compared with bread that contains a well-developed preferment. By taking five or ten minutes today to scale and mix a sourdough or poolish, we significantly reduce the length of the bulk fermentation time required tomorrow. The preferment immediately incorporates acidity and organic acids into the dough, serving to reduce required floor time after mixing. As a result the baker can divide, shape, and bake in substantially less time than if he or she were using a straight dough.
- Rye flour offers some specific considerations. When baking bread that contains a high proportion of rye flour, it is necessary to acidify the rye (that is, use a portion of it in a sourdough phase) in order to stabilize its baking ability. Rye flour possesses a high level of enzymes compared to wheat flour, and when these are unregulated, they contribute to a gumminess in the crumb. The acidity present in sourdough reduces the activity of the enzymes, thereby promoting good crumb structure and superior flavor.