INTRODUCTION

Leavening is increasing the volume or surface area of a dough or batter by creating gas bubbles within it to puff it up, thus making it light.

TYPES OF RAISING AGENTS/METHODS

1. Yeast (Biological)
2. Baking Powder (Chemical)
3. Whisking or Beating (Mechanical)
4. Folding or Rolling (Lamination)
5. Combination of the above.

Yeast (Biological):

Yeast is a form of plant and a living micro-organism. It requires food, moisture, warmth and air for its growth. The yeast act with the sugar and release carbon dioxide gas, so that the aeration process can take place in dough. It also helps in ripening and mellowing the gluten (Protein) of the dough and it contains Vitamin B complex.

When yeast is diluted in water at a suitable temperature and mixed in flour along with the other necessary ingredients for fermentation,  it helps yeast to build up new cells and to raise the volume of product by aeration.

The points to be kept in mind while using yeast:

• It remains idle or dormant in cold.
• It rises in warmth
• If the temperature is high, yeast will become dead.
• One should use strong or hard flour while using yeast for making bread.

TYPES OF YEAST:

1. Dry Yeast: it is a mixture of yeast with corn meal or starch pressed into cakes and dried.
2. Activated Yeast: It develops faster than dry yeast and it is less perishable than compressed yeast.

Baking Powder (Chemical):

Baking powder is a best combination of an acid and an alkali. The carbon dioxide which is generated passed into the air cells already created and is locked in the gluten in the dough.

Chemical aeration is brought about by the production of carbon dioxide from the action, in a solution of an alkali and an acid. Baking powder helps the dough to become light and digestible after cooking.

Whisking or Beating (Mechanical):

This is a method of incorporating air by whisking, beating and sieving ( by using hand, whisk, spatula or by a machine, it is called Mechanical aeration method. One of the best examples of mechanical aeration is the sponge cake, where foam is produced from the eggs and sugar, the flour is then folded in the sponge and baked.

Folding or Rolling (Lamination):

Lamination acts as a raising agent. In pastries folding and rolling helps to give the lift. In Idlis, khaman dhoklas etc. steam formed by the heat helps to puff up, as liquid and flour are present in equal quantities. While making puff pastry 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.

Combination of the above:

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