Sourdough used to be made using wild yeasts. The wild yeasts, particularly in San Francisco create a special flavor in breads. A number of sourdoughs are actually hundreds of years old. The starter or sponge is described as a water and flour mixture that has the yeast used to rise the bread. You can get dried versions of these too and activate these. You can make your own sourdough starters by acquiring local wild yeasts.
About Yeast Measurements
When using different kinds of yeasts in bread making recipes, you have to ensure that the conversion is accurate. Multiply the amount of instant yeast by 3 to get the corresponding amount of fresh yeast. Multiply the amount of active dry yeast by 2.5 to get the corresponding amount of fresh yeast. Multiply the amount of instant yeast by 1.25 to get the corresponding amount of active dry yeast.
More Info
The expiration date of yeast is printed on the package. Yeast can expire, and usually lasts longer than the date printed on the packet if it is kept inside the refrigerator. I can last longer if placed inside the freezer. Testing yeast can be done using sugar. To test, you can add 1/2 teaspoon of sugar to the yeast when stirring it into the water to dissolve. If the yeast foams and bubbles within 10 minutes, the yeast is described as active and alive.
The Yeast Starter
You can easily make your own yeast start by taking equal parts of water and flour. Mix them together and leave everything in a warm location. Leave the mixture for 2 days. Afterwards, the starter should appear frothy. The flour and water should have developed by then. The water will also have a distinct smell at the top. This will be the starter of wild yeast.
Making Sourdough Starters
To make sourdough starters, take a cup of starter from a known bakery. Add water and flour to the starter to make more. The starter can go on for decades. You can make the sourdough starter using normally packaged yeast that you can purchase at a local dealer. You can also purchase packaged sourdough starter mix at the grocery. The internet actually now has several dealers and sellers of sourdough starter mixes. All you need to do is make the order, pay the seller through money transfer or credit card, and have the item shipped right to your doorstep in a few days.
Using the Starters
Make sure you save up some of the homemade starters so you can continue developing these for months and years to come. You will need the yeasts and sourdoughs depending on the type of bread you want to make. You will find that these also lead to certain features and characteristics, depending on how much you put in and the kind of ingredients that you add to the mix. Make sure you also place the starters in the right container, so that these do not expire and you retain the properties that lead to quality and great taste.