Here is an excerpt from my note about poolish that is handed out to PANARY students when they attend a course which has used this type of sponge in one or two of the breads on the programme.
This is the French term for a type of pre-fermentation that forms a portion of the dough into which it is incorporated many hours later or, possibly, the next day. It belongs in the category of the large family of what we call in English “sponges” and “ferments”, and some would call it a “starter ”.
One of its distinctive features is that it is a fairly liquid fermented culture, and in modern baking is usually made with equal amounts of flour and water. It is leavened with factory-made baker’s yeast, and is prepared with part of the main dough’s flour and water. The rest of the dough’s flour, water, salt, and yeast are added at dough-making time. Its flour as a proportion of total flour ranges from 15% – 50%.
In large commercial quantities, in the ambient warmth of a bakery, if the poolish is set to mature slowly over 8-10 hours or more, the amount of yeast added is miniscule, being only 0.1%, which is one gram of yeast to each kilogram of flour. Household bakers could use a little more. When I prepare a tiny poolish at night for a small dough in the morning I describe the amount of fresh yeast used as being the size of a green pea. If conditions were cold, or it was going to sit for less than 8 hours, enlarge the green pea to a marrow-fat pea. With dried yeast, it is only a pinch, denoting an eighth or a tenth of a teaspoon.
As a preliminary fermentation its function in breadmaking is to bestow benefits on the final dough. The benefits are many: flavour, moisture retention, and the creation of the open structure with large and randomly distributed gas bubbles so peculiar to the continental style of breads. Hence it is commonly associated with the baguette. The Parisian baguette was developed as bakers copied the remarkable and innovative pastry and bread methods of Vienna. These innovations occurred in the mid-nineteenth century, probably in the late 1840’s, just before fresh baker’s yeast (saccharomyces cerevisiae) began to be made in factories. At that time, when bread bakers still obtained their yeast from beer brewers (also saccharomyces cerevisiae) a shortage of yeast occurred when many brewers were changing from top-fermenting tanks to bottom-fermenting. Collection of yeast froth is easy from top-fermenters, but difficult from the bottom fermenting types of beer.
The sponge method certainly makes a small amount of initial yeast go further. For a short period the style and skills of Polish bakers must have influenced the Austrians. We assume the Poles’ technique became known as the poolish. Its sparse use of yeast would have continued to be attractive to the bakers of the 1850’s when compressed yeast remained scarce and expensive, being a new product.
A poolish must be set to work at room temperature for at least 3 – 8 hours before it is added to a dough, possibly 12 – 15 hours if conditions are cool. On the other hand, if conditions are warm, after 3 – 4 hours it would be wise to put it in a refrigerator. Although it starts with only a small amount of yeast it gets surprisingly active at room temperature because after about 5 hours those yeast cells start to reproduce. They will continue to multiply while they have food. (In any type of dough or sponge yeast will begin to reproduce after some 4 to 6 hours). After its long fermentation period the poolish will be classed as mature and ready for use because by then the feeding yeast will have created acids and by-products from their fermentation activity, and these will greatly enhance the dough that receives the poolish. More yeast has to be used if it is expected to reach maturity in a shorter time, such as 4 – 5 hours. There will be more flavour in the final bread, the crumb will be porous and open while giving a satisfactory chewiness, and the bread will retain its moisture for longer – meaning it is slower to stale.
The appearance of it when ripe reveals many bubbles on its surface, with the gas bubbles looking as though they are pushing upwards to burst. It is classed as over-ripe if it has begun to sink or settle down, and is no longer appearing to be moving upward. When over-ripe it may reveal around the sides of its storage vessel a line indicating the “high-tide” level that it had reached before sinking or collapsing.
500 gm breadmaking white flour
500 ml water
½-1 gm fresh yeast ( ⅛-¼ teaspoon dried yeast)
Mix until a loose, batter-like dough is formed, with no dry patches.
Cover the bowl you have mixed it in, and put it aside in a quiet place for it to ferment for 8 to 12 hours.
That’s it. I hope you enjoy working with sponges and tinkering with poolish in particular. Good baking, Paul