Aerating Agents (Bakery)

AERATING AGENTS

Aeration renders bakery products more attractive, more appetizing and digestable. In order to aerate a pressure must be induced within the product and a resistance offered to it so the volume may be increased during baking until such time as the proteins coagulate and the volume is maintained without collapsing.

There are five methods of aeration--------

1. Panary-----yeast
2. Chemical------ baking powder.
3. Physical-------whisking and baking.
4. Lamination-----rolling and folding .
5. .Combination --- of the above.

Panary-----

The principle of panary fermentation is the production of carbon-dioxide. This is brought about by the action of enzymes in yeast and flour.The initial gas production comes from the breakdown of glucose present in the flour or contained in the added ingredients. Further glucose is made available by the conversion of other carbohydrates by specific enzymes. The gas is entangled and held in the gluten network which is gradually made more elastic during the fermentation process and so the dough rises.There are acids and alcohol by-products in the fermentation process which contribute to the flavour.

In the oven the gas production is accelerated until at last the yeast is killed and activity ceases the expansion of air and gas and the pressure of water vapour causes an increase in volume which is maintained by the coagulation all the proteins present as bakeing proceed.

Chemical:-

Various chemical substances are used for aerating cakes. All of them when moistened and heated produce gas which by becoming entangled in gluten network of the mixture from which it readily cannot escape, causes the of volume of cake to increase while in the early stages of baking in the oven.
Baking pd can be defined as any substance or mixture of substance which may be purchased at an economical price, which when moisten and heated will produce a gas to aerate confectionary and which will leave a harm less and practically tasteless residue in the goods.
Sodium bicarbonate or baking soda is used either alone or mixed with an acid of some kind to provide the necessary gas for aeration twice as much gas carbon dioxide is produced from a given lot of sodium bicarbonate. When suffcient acid is present to release al the gas contained in it compared with amount of gas given off when NaHCO3 is moistened and heated without the precence of an acid.
NaHCO3 is used alone in the aeration of some kinds of confectionary, chiefly in cakes which are strongly flavoured and which have dark coloured crumb {ginger cake}
2NaHCO3 = Na2CO2 + H2O + CO2
Soduim bicarbonate = Sodium Carbonate + water + Carbondioxid

Cream Of Tartar Sodium Bicarbonate
In order to obtain all the gas which is available in any definite quantity of so NaHCO3 and acid must be used along with it. The acid substance is generally potassium hydrogen tartrate commonly called cream of tarter. When mixed in the correct proportion and heated in water they produce CO2 , water and potassium sodium tartrate Rochelle salt.

KHC4H6O6 + NaHCO3 = KNaC4H4O6 +CO2 + H2O
The combining weight used in bakery is usually two parts of cream of tarter and one part of sodium bicarbonate but these leaves an access alkalie in the goods {from the above equation it is seen that 22.4 part cream of tarter required 10 parts sodium bicarbonate for complete neutralasation} 2:1 ratio has insufficient cream of tarter to neutralize all the sodium bicarbonate in other words a small quantity of sod does not enter the reaction this excess acts as stated previously leaving a residue of NaCO3 in the goods which affects crumb colour it is for this reason that for all good recipe for white crumb cakes an extra quantity of cram of tarter is added is used.
Baking powder can be made with 11 ¾ lbs cream of tartar and 5/4 lbs sodium
bicarbonate to give an all round result

Physical-----

Long ago in our gastronomic history it was discovered that by beating a mixture air was incorporated and the baked product became lighter in texture. There are two important bakery materials that are capable of holding air when beaten, they are eggs and fats.

The principle behind physical aeration is that the rapidly moving hand whisk or beater breaks the surface on impact and moves into the mixture, temporarily extending the surface area.

The surface area will strive to remain at a minimum thus offering a resistance which drives the mixture behind the beating equipment as it penetrates still further into the mix.
It is during this fractional moment of time before the beater strikes again that air bubbles are drawn into the mixing until at last it is thoroughly aerated ,

Lamination--------

The purpose of rolling and folding is to build up a laminated structure of alternating layers of dough and fat. This build up is known as aeration by lamination. Gluten is insoluble wheat protein, hydrated in the ratio of one part protein and two parts water
IT is the changing of water into steam and the consequent pressure within the gluten structure that is largely the reason for the lift. When the pastry is baked the fat melts and forms an oily layer between the leaves of the dough and preventing them from sticking together; the heat penetrates further into the the paste, the water in the doughy layers is
Changed into steam distending the gluten films of the dough and so pushes the lubricated leaves of the dough apart. This produces a great increase in the volume.Later the gluten of the flour is coagulated while the water in the dough dries out so that by the time the paste is properly baked it is able to retain its distended puffy volume Temperature of the oven is important. If baked in too cool an oven the paste will not puff up to the fullest extent.

Combination of methods--------

Combination of two of the above are used to produce different types or differing qualities of confectionery.
Danish pastry is a combination of aeration by yeast and by lamination.

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