Question

1. What mechanisms are used for leavening quick bread and provide examples of the process & a product in which each is used.

Answer 1

****what are the mechanism for quick leaveining of bread and its various process are as follows::

******** Leavening or raising means to increase the surface area of any dough or batter by creating gas bubbles inside the dough or batter. This also makes a product light in weight. The expansion of gas bubbles during baking increase the volume of the product and gives a desirable porous structure. Raising agents that are used in the kitchen can be classified into the following categories:

1) Biological (Yeast).

2) Chemical (Baking powder, baking soda, baking ammonia).

3) Mechanical (Beating, whisking, creaming, sieving).

4) Lamination.

5) Natural Leavening Agents.

1) Biological Raising Agent:

a) Yeast: Yeast is a tiny living fungus and can be of two types 1) Fresh or compressed Yeast and 2) Dry Yeast and It thrives on sweetness, warmth and moisture. As the yeast eats, it excretes carbon dioxide and alcohol. It is this gas which causes a rise in the baked product.

The Alcohol evaporates during the baking process, yet helps in the development of flavour in the bread. And because yeast is a living organism the baker's main goal is to control the point of death of the yeast. The scientific name of yeast is Saccharomyces Cerevisiae. Yeast is unicellular microscopic fungi and the structure of yeast consists of a) Cell wall b) Protoplasm and c) Vacoale.

Yeast, whether it is compressed or dry is usually stirred into a small amount of warm liquid and allowed to stand for at least five minutes to dissolve.

b) Food: Simple sugar like dextrose or fructose.

c) Suitable climate: 80 to 85 degree F, at least 70% humidity can give the best result.

d) Fermentation activity: The protoplasm of yeast contains the following enzymes:

Invertase: It converts cane sugar or sucrose into a simpler form of sugar which is known as invert sugar, which is a combination of dextrose and fructose.

Maltase: It converts maltose sugar into dextrose which can be directly fermented by yeast.

Zymase: this is the most important fermenting agent which breaks invert sugar and dextrose to carbon dioxide, some amount of pure alcohol, and a very small amount of glycerine, acetic acid and some amount of lactic acid. It also produces some flavourful aroma which gives a pleasant fermentation flavour.

Protease: It softens down the flour protein, thus gives a better stretchability for the bread (to be specific on gluten) so that it can get a good volume and structure.

e) Storage of yeast: Stored at 45 degrees F. Yeast is killed by heat in a range of 127 degrees to 140 degrees F.

f) The symptom of damaged or rotten yeast:Buttery consistency, Brownish in colour, Crumbly in texture, Very obnoxious smell. If the baker has any doubt about the freshness of the yeast then it should be proofed.

Tip! - Method of proofing yeast:

Dissolve yeast in 1/4 cup of warm water with one teaspoon of sugar and two tablespoons of flour. If the yeast is active it will be spurred on by the sugar and fed by the flour. Within ten minutes the yeast should begin to expand and foam. The proofing of yeast before adding it to other ingredients will save time and expense.

2) Chemical Raising Agent

A chemical raising agent is brought about by the production of carbon dioxide in a solution of acid and alkali, in the presence of heat.

A) Baking Powder: It is a leavening agent made up of a mixture of an acid reacting salt with bicarbonate of soda. We also add some starch to the mixture to keep it in a dried condition and also to act as a separator between sodium bicarbonate and acid reacting salt, until used.

There are three types of baking powder. 1) Double action - baking powder releases 1/3 of its carbon dioxide at room temperature and the rest during baking. 2) Tartrate - baking powder reacts quicker, as soon as the liquid is added and 3) Phosphate - baking powder is slower and only heat releases its gases.

On the presence of both heat and moisture, the acid reacting salt reacts with sodium bicarbonate and releases carbon dioxide. A part of the gas is entrapped into the gluten structure or small air cells of a batter which already has developed because of creaming action of fat, these structures now expand with the production of the gas and during baking also and the small part of the gas is absorbed by the media itself. Cream of tartar is actually a form of refined tartar which is a by-product or precipitation from the grape wine manufacturing process.

B) Baking Soda: Baking soda which is chemically known as Sodium bicarbonate acts also acts as a leavening agent when mixed with an acid such as sour cream, sour milk, buttermilk molasses or citrus juice. The chemical reaction of leavening agent and acid produces gases which make the mixture rise.

C) Ammonium Carbonate: It is also known as baker’s ammonia or hartshorn, which is in white colour crystalline salt. Since it readily degrades to gaseous ammonia and carbon dioxide upon heating, it is used as a leavening agent and also as a smelling salt. As it also produces carbon dioxide in the presence of heat but because of the strong offensive flavour, it is always to be used with very strong flavouring agents.

3) Mechanical Raising Agents

It is the incorporation of air by beating, creaming, whisking and sieving. Whisking of egg and sugar, creaming of fat and sugar, sieving of flour are the eg of mechanical raising. All these actions involve physical movement hence known as mechanical raising or leavening.

4) Lamination

Lamination acts as a raising procedure where the fat and dough is folded and rolled. The moisture incorporated in the fat and in the dough also will vaporise during baking and gives it the lift (or raising).

5) Natural Leavening Agents

Steam: Steam can be used as leavening agents for cooking that is done at very high temperatures. The batter must be capable of holding in the steam until it is set. Steam gives the effect of leavening as it expands upon heating. This way of cooking is generally applied in popovers and Yorkshire puddings.

Air: Air is another leavening agent that can be incorporated by beating the batter thoroughly with Mechanical leavening agents. The trapped air expands upon heating.