Author Topic: Leavening  (Read 4587 times)

Offline Delmonico

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« on: August 11, 2010, 05:57:54 PM »

Yeast is a single celled fungus that reproduces by budding and produces CO2 and alcohol from carbohydrates and sugars.

This CO2 can be used to make bread light and fluffy.

For thousands of years, yeast was grown at home by many methods and preserved by many methods for use is leavening bread.  Sourdough is the most well known.  More on sourdough another time, but sourdough is multi-useful because in can induce acid for quick breads or yeast for yeast type.

Yeast was also bought from brewers and some small-scale production was done on a local basis.

This all changed in 1876 when at the Centennial Expo in Philly, Fleischmann's introduced massed produced, controlled product yeast, with grand baking demonstrations.

This yeast was in the form of a cake that kept fairly well if kept cool, but still had a shelf life of only a few months, but it made good baking much simpler and with the new mass transportation provided by the railroads, all but the most isolated could buy it in most stores.

The dry yeast we are most familiar with came on the market in the early 1920's and keeps much better and has a better shelf life.

Cake yeast is still made and is easiest to find around the winter holidays, it costs from about 5 to 100 times or even more than dry yeast.  (I buy my yeast in 1 pound bags.  One cake of yeast is the same as one package of dry yeast.

The reason for cake yeast to even be made today and why it is easier to find at the holidays is that many families have recipes that have been handed down for several generations and these are most often made at Christmas and Thanksgiving.  And if Great-Grandma wrote to use 2 cakes of yeast, well what do you do?

I did some research on this, because many of my old recipe books call for it.  My Grandma Carman had a recipe from her Grandma she made at Christmas that called for it and she used cake yeast for it.

Well a 1-800-number to Fleischmann's several years ago got me into a person who told me there is no difference in the final product if you proof it like the old folks did.  This is to prove your yeast ain't dead before you waste expensive indigents.  Most old recipes call for this.  You mix the yeast with some warm water and some flour, a tablespoon or so per cup of water.  Cover and if in half our or so there is foam on top, it will prove your yeast is fine.

I use dry yeast in all my historical cooking because of cost, the last I bought was two 1 pound bags of yeast for about $6 the last cake of yeast I bought was $2.50.

I freely admit to folks who are interested what the change is from PC.  Since it is not unusual for me to make 20-30 pounds of yeast bread in a couple of days at an event one can see that the cost difference is quite a bit.

(I bake 500-700 pounds of flour in the average year.

Chemical leavening

Leavening is the process that CO2 gas is induced into dough to make the final product lighter and fluffier.  This is sometimes done by yeast converting carbohydrates and sugars into alcohol and CO2 gas; this takes time, often several hours.

A chemical reaction can also be used to do this very quickly, hence the name "quick bread."

If you don't understand how this works, put a couple of tablespoons of baking soda in a glass, put the glass in the sink and add a cup of vinegar.

Sodium bicarbonate (NaHCO3) is the chemical name for baking soda, also called salertus in old recipes, var. of sal aeratus, meaning aerating salt.  This came on the market in the 1830 and when mixed in a recipe with an acid substance like molasses, sourdough starter, cream of tarter or one of many acids, it makes CO2 like the baking soda/vinegar experiment.

Before this Pearl Ash, a high quality ash made from controlled burning of hard woods added the alkaline substance to mix with the acid to raise a dough quickly. 

(And you thought you'd never use that High School Chemistry.  )

Baking powder came on the market in the early 1850’s; it was often called yeast powder although it contains no yeast.

The early baking powder was a mix of two parts cream of tarter to provide the acid for the reaction, 1 part bicarbonate of soda to provide the alkaline part of the reaction and 1 part cornstarch to prevent caking.

When wetted in mixing this formed CO2 gas to leaven the mixture. This is called a single-acting baking powder and the product needs cooked as soon as possible before the reaction stops.

Around the late 19th century a more expensive product called double-acting baking powder came on the market. These are different chemical mixes, but wetting starts the reaction and heating finishes it, this allows more time to bake a product.

Double-acting baking powders are considered more fool proof than single-acting types, but some say they add an undesired taste to the final product.  Also in times past the cost of double-acting was more.

Some single-acting are still on the market and are hard to find, cost is not much different today if you can find the single-acting type.

Of course you can always mix your own if one desires to make their baking more historically correct. 

Single Acting-Baking Powder

2 parts cream of tarter
1 part Baking soda
1 part corn starch (to prevent caking in storage)

Sour dough

Sourdough is one of several ways of growing you own yeast; it dates back thousands of years.  To use $10 words it is a symbiotic relationship between yeast and one or two types of bacteria.

Basically it is a carbohydrate suspended in a liquid, usually water and flour, in this mix grows a form of yeast that turns the carbohydrate into alcohol and CO2.  Also there is an acetic type bacterium that changes the alcohol into acetic acid. (vinegar)  Also in most cultures there is a lactic type bacteria that turns some of the carbohydrates into lactic acid (like sour milk)

The yeast can be used to raise bread just like store bought yeast although it is less fool proof and takes longer.  Also the acid in the sourdough can be used with an alkaline substance to for CO2 to leaven the bread
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