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RAISING AGENT / LEAVENING AGENT


RAISING AGENT / LEAVENING AGENT

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 kitchen can classified into following categories:

  • Biological (yeast)
  • Chemical (baking powder, baking soda, baking ammonia)
  • Mechanical (beating, whisking, creaming, sieving)
  • Lamination
  • Combination of all

BIOLOGICAL RAISING AGENT

1) Yeast can of two types:
  • Fresh or compressed yeast
  • Dry yeast

The scientific name of yeast is Saccharomyces Cerevisiac. Yeast is unicellular microscopic fungi. The structure of yeast consist :
  • Cell wall
  • Protoplasm
  • Vacoale

2) Food: Simple sugar like dextrose or fructose.

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

4) Fermentation activity: the protoplasm of yeast contains following enzymes:
  • Invertase: it converts cane sugar or sucrose into 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 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.

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

6) Symptom of damaged or rotten yeast:
  • Buttery consistency
  • Brownish in colour
  • Crumbly in texture,
  • Very obnoxious smell.

CHEMICAL RAISING AGENT

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

1)      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.

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 tarter is actually a forum of refined tartar which is a by product or precipitation from grape wine manufacturing process

2)      Ammonium Carbonate: it also produces carbon dioxide in presence of heat but because of the strong offensive flavour, it is always to be used with very strong flavouring agents.

MECHANICAL RAISING AGENT

It is 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.

LAMINATION OR WATER VAPOUR

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).

In indian cuisine , idlis and dhoklas are steamed where heat helps to puff up the final product by vapourising the steam. In popcorn, the corn pop because of the moisture present inside and ultimately its volume increase. In choux pastry water vapour acts as raising agent.

COMBINATION OF ALL

Danish pastry is an eg of combination raising where we use yeast in the dough and fat is used by lamination process. Some other eg are vanilla buns, fruit cake etc, where we use whisking, creaming and chemical raising agent.

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