Sponge & Dough, Sourdough Starter Propagation.

What is Sourdough Starter?

Sourdough starter is the leavening agent in sourdough bread that denotes the characteristically unique, sour flavor. Sourdough starters originated in Egypt when Egyptians would reserve small pieces of dough to help with the next day’s bake. Bakers who had lighter bread became better known for their starters, and were encouraged to keep them active.

The sourdough starter is simply combined by flour and water and left to sit or ferment. In the first week, it is necessary to “feed” the starter additional water and flour every twelve hours, and every twenty-four hours following the first week. When mixed together, flour and water activates the amylase enzymes, which breaks down starch into maltose. This maltose is then broken down further into glucose, which is yeast’s food. The feeding yeast produce carbon dioxide, which is what makes the starter rise. Lacto bacilli are also produced in this process, which create lactic acid that gives sourdough its distinct flavor.

The starter generally comprises between 5 and 50% of the flour weight in bread. In San Francisco, the starter comprises 40% of flour in the dough. There are many kinds of starters, including those with additions of organic grapes, basil, and water from boiled potatoes. Grapes have natural yeast in their skin, allowing the starter to grow faster. Basil is common in Greece and also used for the additional yeast. Potato starch gives additional starch to increase rising in “levain” as well.

Sourdough Starter Formula

Ingredients

1. ? cup flour. Typically bread flour or all-purpose unbleached flour

2. ? cup warm water. It is important to have filtered water so that the chlorine found in much of the tap water will not kill yeast.

Method

? Mix together flour and warm water gently, in a container that is at least twice the size as the initial mixture.

? Cover the mixture with a cloth, make sure it is not completely air tight, as natural yeast from the air will help the sourdough starter grow faster and add additional flavor. Let this sit in a warm place for twelve hours.

? After twelve hours, add an additional ? cup of flour and ? cup of water, stir again, and let the mixture sit again for twelve hours.

? Continue to refresh this mixture with additional flour and water in equal proportions for 2 to 3 days, to ensure that the starter is established. The starter is established once it doubles in size easily, containing large air bubbles. When

this is achieved, it is ready for use. The starter can be used anywhere up to 50% of the total dough, for a stronger smelling sourdough bread.

?The starter needs to be refreshed by removing ? cup of the starter, before mixing in another ? cup flour and ? cup water.

?After this, store the starter in a container and continue to refresh the starter once every twenty-four hours at room temperature. As long as it is being refreshed, the starter will stay active and continue to make sourdough. Starters can literally last decades, and older starters are often preferred for their consistency and stability.

? If a brown liquid appears on the top of the starter, simply poor this layer off. It is called the “hooch” and signifies that the starter received too much water. Although this layer will protect the sourdough from growing mold on the surface during its conservation.

? Do not let a starter sit at room temperature for more than three days, and do not let a starter sit in a refrigerated environment for more than one week without refreshing it. If this happens, the acidity of the starter will be compromised and the gluten structure will not b

What is the sponge and dough method?

Sponge and dough is a breadmaking method that involves two stages:

1. A pre-fermentation step for sponge mixing

2. A dough or final mixing step.

It produces breads with unique flavor and aroma, a soft crumb and an improved shelf-life. For this reason, this method is commonly used in pan bread, buns and other bread varieties. It is popular in Asian countries, North America and Central Europe.

How sponge and dough works

The sponge and dough method consists of two distinct mixing stages.

Stage 1: Making the sponge In this stage, 60%–90% of the total flour is combined with water at room temperature to a 58–65% hydration level (based on sponge flour weight). Then, compressed yeast at 1.5–5.0% (based on total flour weight) is added and shortly mixed just to incorporate ingredients. Next, fermentation follows for 2–8 hours at 75–85°F (24–29°C) and relative humidity of 60–80% to produce the sponge.

Sponge fermentation time varies with:

? Temperature

? Ingredients used

? Amount of yeast

? Available food like sugars and damaged starch in flour

? Amylase activity of flour

? Water absorption of sponge

? pH of sponge

In small-scale sponge production, the sponge is mixed and stored in the mixer. However, in high-speed bakeries, a separate container such as a trough is used to store the sponge in a fermentation room under controlled conditions. Occasionally, the sponge must be knocked, or punched down, to prevent it from spilling over.

Stage 2: Making the dough The sponge is added to the remaining liquid and dry ingredients and mixed for 8–16 minutes in a horizontal mixer to form a dough of optimum gluten development. Then, the dough goes to the makeup stage, where it is proofed and baked.

Once pre-fermentation is complete, the sponge:

? Expands 4–5 times its volume

? Is very soft, pliable, extensible, with an open cell structure

? Has risen 8–10°F (4.5–5.5°C) in temperature.

? Has a temperature of 84–88°F (29–31°C)

? Has a pH of 4.8–4.9

? Has a total titratable acidity (TTA) of 4.5–4.6

Commercial production

The sponge and dough system is still popular in small bakeries but has been gradually replaced in commercial bakeries by faster production systems such as the straight or no-time dough.

When using a sponge and dough system, commercial bread manufacturers use a combination of mixing methods that include horizontal and Tweedy mixers. Automation and ingredient handling systems have created faster production times and a semi-continuous mixing fashion with sponges being produced without schedule interruption to feed the sponge and dough system.

Application

Since the sponge and dough is already ripe prior to mixing into the final dough, in addition to accelerating fermentation, it is itself a partially developed dough. So, these aspects help in reducing mixing time.

The best flour to use in the sponge is:

? Milled from hard wheat

? 13–15% protein content

? Sufficient level of damaged starch to provide food for yeast

? Optimum amylase activity (Falling Number of 200–250 seconds)

Along with temperature and time, TTA and pH measurements are the best and most practical ways to control and monitor the sponge fermentation step. Acidification of the sponge is an indication of good fermentation and enzymatic activity.

Advantages and disadvantages of the sponge and dough system

Advantages

? Good fermentation tolerance, ability to correct dough fermentation mistakes.

? Unique fermentation flavor and aroma.

? Improved finished product characteristics:

o Finer crumb grain

o Silkier, smoother texture

o Moist and pleasant mouthfeel

Disadvantages

? Less mix tolerance. The sponge and dough are both sensitive to over-mixing given the biochemical development during pre-fermentation.

? Longer fermentation time

? Longer production time

? Increased need for equipment and space to ferment sponges