Sponge and dough

Thesponge and doughmethod is a two-stepbreadmaking process: in the first step aspongeis made and allowed to ferment for a period of time, and in the second step thespongeis added to thefinal dough'singredients,creating thetotal formula.In this usage, synonyms forspongeareyeast starteroryeastpre-ferment.In French baking thesponge and doughmethod is known aslevain-levure.The method is reminiscent of thesourdoughorlevainmethods; however, the sponge is made from all fresh ingredients prior to being used in the final dough.
A sponge ferment is usually a sticky process that uses part of theflour, part or all of thewater, and part or all of theyeastof a total- orstraight-doughformula.  Highly liquid sponges of batter consistencies are mixed with a whip, spoon, or fork. Lower hydration, stiffer sponges are lightly mixed or kneaded just until the dough begins to develop. The sponge is allowed to rest and ferment for a period of time in an environment of a desired temperature and humidity. When the sponge's fermentation time has elapsed or it has reached a desired volumetric growth characteristic, thefinal dough'singredients are added. Thegluten is developedin the mixing or kneading process, and it may then be processed through furtherworkandrestcycles before beingproofedthen baked.
The sum of the sponge and final dough's ingredients represents the total formula.A generic 65% pre-fermented flour sponge-and-dough formula usingbakers' percentagesfollows:
The sponge's fermentation time depends on itstemperatureand that of the surrounding area, the ingredients used, and the percentage amount of yeast. It ferments in a humid environment at 74–78 °F (23–26 °C), where it mayriseand expand to 4-5 times its original volume, when itfallsit has reached 66-70% of its allotted time.
One significant decision the baker must make when designing such a formula, or adapting adirectorstraight-doughformula or recipe, is to decide the sponge-to-dough flour ratio.While the relative amounts of ingredients used may vary, the method remains the same.
The sponge method is used for 3 different reasons:taste,textureandchemistry.
The flavour that is created is dependent on the ingredients used and the fermenting yeast. Just like sourdough, the longer the ferment, the greater the taste difference.
Sponge doughs were used beforebread improverswere invented. Texture is partly a byproduct of the chemistry going on in the fermentation, which does several important things such as activate the differentenzymes(proteaseandamylase) needed to leaven bread. Modern grain-harvesting practices have reduced the naturally occurring enzymes that grains had in former times, a result of no-longer-used grain-storage processes,so today small amounts of enzymes are routinely added to flour by manufacturers,often in the form ofmalted barleyorsprouted grain.
Proteases, dependent on their time of action and concentration levels,soften theglutenin the dough, hydrolyzing peptide bonds,increasing doughextensibilitywhich allows the protein matrix to stretch out as the mix expands, thus leading to increased baked volumes and better structure.
Many bread recipes call for a sponge method, especially traditional French breads. Some examples of breads that use the sponge method: