Close this window
RAISING AGENT
A raising agent or leavening agent is any one of a number of substances used in dough and batters that causes a foaming action that lightens and softens the finished product. Formation of carbon dioxide is induced by chemical agents reacting with moisture, heat, acidity, or other triggers.
TYPES OF RAISING AGENTS
1. Chemical raising agents 2. Mechanical actions as raising agents 3. Natural leaveners as raising agents: 4. Combination method
CHEMICAL RAISING AGENTS
The main three Chemical Leaveners used in Baking are:
· Baking Soda and
· Ammonium Carbonate.
Baking Powder is a blend of acid (most commonly calcium acid phosphate, sodium aluminium sulphate or cream of tartar) and alkali – (baking soda/sodium bicarbonate). These create carbon dioxide bubbles when liquid and heat are added.
Commercial baking powder uses several compounds which gives it a double action. It acts when liquid is added and once again when heat is added after you put your product in the oven.
Baking Soda (Bicarbonate of Soda), is used when there is already an acid ingredient in the recipe such as:
Applesauce, buttermilk, brown sugar, chocolate, cocoa powder, cream of tartar, honey, lemon juice, molasses, vinegar.
When baking soda comes in contact with an acid and liquid is added, carbon dioxide (CO2), water and a neutral salt are produced. Care must be taken with how much baking soda is used. If too much - a ‘soapy’ aftertaste remains and the product bakes darker. If not enough is used - an acid flavour remains.
Baking soda is much stronger than baking powder. The general rule is to use 1 to 1-1/4 teaspoons baking powder per half cup of flour, (4ozs/100g). Baking soda should be added at 1/4 teaspoon per half cup of flour, (4ozs/100g).
How do these chemical leaveners work?
When carbon dioxide is released by either baking soda and/or baking powder, it first dissolves in the liquid. When this becomes saturated, the carbon dioxide produced turns into the air bubbles which expand. Towards the end of baking the bubbles set. You have a well risen product showing tiny air holes when cut.
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 ACTIONS as RAISING AGENTS:
· Creaming method · Kneading method · Whisking method
The physical actions of creaming, kneading, beating, and whisking will incorporate tiny air bubbles which expand when heat is added. The addition of flour gives structure for the air bubbles to work against - you get rise. This structure is fixed in the oven by heat.
Creaming Method: Fat and sugar are creamed together until the sugar crystals melt and the whole mass takes on the consistency of whipped cream. Use castor sugar which has a small crystal size. It will combine with the fat far easier than granulated sugar, which has a larger crystal. The creaming method incorporates air into the mixture which is held in place by the semi-solid fat. These bubbles expand during baking allowing the batter to rise. Care must be taken once flour is added. This should be folded in carefully to avoid development of the gluten lattice structure. You will get a cake with a better texture and more rises by using special cake flours here - they are low in gluten.
Kneading is a process used in bread making. Yeast liquid is dispersed into high gluten flour to make dough. The mechanical action of kneading the dough, either by hand or machine develops the gluten strands which form into a lattice structure. As gentle warmth is applied, carbon dioxide is released by the yeast and is trapped in pockets; these continue to expand until heat is applied during baking. Heat kills the yeast off and fixes the gluten's lattice structure in place, which leaves you with a well-risen, light, loaf.
Whisking: When volume has to be added then the whisking method is used. Meringues are made by whisking egg whites with sugar until the volume is six to eight times more than you began with. Gentle heat applied over several hours dries out the meringue and leaves a crisp, sweet confection. Fatless sponge cakes require whole egg and sugar to be whisked together to achieve a high volume. Cake flour is gently folded in. Air incorporated into the egg gives volume and lightness to the cake.
NATURAL LEAVENERS as RAISING AGENTS:
· Yeast · Steam
Yeast is a natural leavener. Give it food, moisture, warmth and air and it will grow. During this ‘fermentation’ process the carbon dioxide gas released by it is trapped in tiny air cells. These continue to expand and push up against the latticed gluten structure and rise! The lattice structure is formed and developed when water is added to the wheat protein (gluten), and then kneaded together.
It takes about 2 hours using fresh, active dry, or, instant active dry yeast, for the bread to complete this proving stage. The baking process stops the action of yeast cells by killing them and fixing the lattice structure of the wheat protein (gluten). Sourdough – a natural process using air borne yeast cells can take up to 24 hours to reach the stage for baking. This lengthy process produces bread with a wonderful aroma and flavour.
Yeast can of two types:
1. Fresh or compressed yeast
2. Dry yeast
The scientific name of yeast is Saccharomyces Cerevisiac. Yeast is unicellular microscopic fungi. The structure of yeast consist :
1. Cell wall
2. Protoplasm
3. Vacoale
Food: Simple sugar like dextrose or fructose.
Suitable climate: 80 to 85 degree F, at least 70% humidity can give the best result.
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.
Storage of yeast: Stored at 45 degree F. Yeast is killed by heat in a range of 127 degree to 140 degree F.
Symptom of damaged or rotten yeast:
· Buttery consistency
· Brownish in colour
· Crumbly in texture,
· Very obnoxious smell.
Steam is the most basic of raising agents, but also the most complex in technique. In puff pastry, the layers of butter and pastry are heated. The butter lets off steam which pushes up against the pastry leaves and you get rise. Once the steam has evaporated, the pastry leaves are set in place by heat during baking. With choux pastry and Yorkshire puddings, steam is released from the wet batter which pushes up against the gluten lattice and you get a puffed up pastry, again, fixed by the heat of the oven. In both cases, strong flour is necessary to give a lattice structure which will not break through the force of steam.
COMBINATIONS:
Danish pastries are a combination of aeration by yeast and lamination. For this, 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.
All raising agents (leaveners) work on the same principal, be it Chemical, Mechanical or Natural. Gasses expand, push up against a structure, you get rise, which is fixed by the heat of the oven. It is by using ingredients and baking techniques in the correct manner which ensures success when we bake
Close this window