raising or leavening agents

Raising or leavening agents : leavening is increasing the surface area of dough or batter by creating myriads of gas bubbles within it to puff it up ,thus increasing the volume and making it light. The expansion of these gases during baking increases the volume of the product and gives a desirable porous structure. The aeration of flour products is affected by the following:

1- biological(yeast)   2- chemical(baking powder)  3- mechanical(whisking/beating)  4- lamination(folding, rolling)  5- combination of above.

1-  yeast: it is a living micro-organism and is a form of a plant live, it requires for its growth food ,moisture, warmth and air. The primary function of yeast is to change sugar into carbon di oxide gas so that the dough in which it is generate it is aerated. It also assists in mellowing and ripening the gluten the dough and it contains vitamin B complex.

When using yeast these points should be remembered –

a)      It remains dormant in cold .

b)      It rises in warmth

c)      It is killed by heat If temperature is over 127 degree F

d)      It is fed by sugar and in the dough it caramelizes on the outside, forming a brown crust.

e)      It is fed by flour , the starch gelatinizes with the moisture inside the dough and cooks into a light spongy mixture which is digestible

f)       Strong or hard flour is the best to use bread making

Commercial yeast is of two main types:-

Compressed in a cake form (also in a liquid form) and dry yeast in granule form.

2- chemicals:-

chemical aeration is brought about by the production of carbon di oxide from the action, in solution, of an alkali and an acid in the presence of heat the acid and alkali in correct proportions, which is harmless to human digestion,is baking powder baking powder consist of two parts acid and one part alkali.

3. mechanical :-

it is incorporating air by whisking , beating and sieving. When sugar and eggs , fat and sugar, fat and flour or any combination of yeast are beaten or whisk together , or flour is sieved , it works as aeration. Whichever way the air is introduced  into the mixing , be it by hen ,whisk ,spatula , or by machine , it is still turn mechanical aeration.

4. water vapour :-

Lamination acts as a raising agent . in pastries – folding and rolling helps to give the lift. In idlis , khaman dhoklas etc. steamed formed by the heat helps to puff up. The fundamental objectives when making puff pastries is to build up a structure of fat and dough consisting of many layers so that when subjected to heat in an oven , it will expand and lift evenly, to produce goods with short heating properties.

5. combination:-

Danish pastries are a combination of aeration by yeast and by lamination . for this a rich yeast dough is made and butter is incorporated as for puff pastries. In this , the pastries expand in volume because of the process of aeration by lamination and at the same time is aerated by the action of yeast.