Egg is a good source of High Biological Value of protein. Albumen (Egg white ) contains about 12 types of protein, ovalbumin, conalbumin, ovomucoid, ovoglobulins & ovomucin.
When egg white is whipped,
DENATURATION
- Ovomucin & ovoglobulin are denature
- They unfold & spread themselves in the liquid portion of the foam
- And form bonds among themselves & other proteins
- Beaten eggs aerate recipes due to their ability to foam and by contributing water for steam in sponge cakes. Foam is created by incorporating air into a mixture
The presence of these denatured proteins in the liquid lowers the surface tension of the foam
- Resulting with a stable foam
During whipping,
- Ovalbumin & conalbumin remain intact
- They are distributed in the liquid proportion of the foam
Upon baking,
- Ovolbumin & conalbumin denture
- And form bonds among the egg-white proteins to form permanent solid foam
COAGULATION
- Protein form egg coagulate upon heating, this provide structure & texture to cake
Crystalline sugar
During whisking,
- Crystalline sugar helps to create air in the batter during whisking. The more delicate its structure, the higher it will rise.
- Sugar helps produce fine crumb texture and good volume during mixing and baking.
- Sugar tenderizes cakes by absorbing liquid(from eggs) and preventing complete hydration of gluten strands.
During baking,
- Sugar tenderizes sponge cakes by absorbing water and keeping batter from setting too quickly, which allows it to rise higher in the oven. In addition, sugar contributes pleasing, sweet flavors and tender browned surfaces to shortened cakes.
Flour
Flour is the basic structural component of sponge cake batter.
Plain flour contain lesser amylose, gluten-forming protein & amylopectin compare to wholemeal flour
During Folding,
HYDRATION
- Gluten firms flour mixture when combined with water
- Water molecules enter the starch granules and hydrate them
-The volume of starch granules increase
During Baking,
- Gluten traps air & allows expansion of air cells, resulting in high volume during baking.
- Gluten denatures during baking & provides rigidity to baked product
GELATINIZATION
- Starch in flour gelatinize, giving strength to the baked product & adding texture
- Starch contributes to crumb. Crumb is partially created during baking by the number & size of air cells produced, degree of starch gelatinization, and the amount of protein coagulate
That is why wholemeal flour has coarse crumb that is large and irregular as it has high content of starch compare to plain flour.
HYDROLYSIS
- Amylose in flour can be partially broken down by enzymes (amylases) which is present in flour into dextrin, malt, & glucose
- These compounds add sweetness, darken the crust colour and improve fermentation, making the mixture lighter in texture.
That is why wholemeal flour taste sweeter as it has a higher content of Amylose
MAILLARD REACTION
-Amine group (protein) from flour and reducing sugar [sugars such as glucose,fructose,maltose but not sucrose] undergo condensation to form glycosylamine. Glycosylamines will rearrange to form colourless intermediates of amadori coumpounds. These compound will undergo polymerization to form brown complexes
A leavening agent provides a source of gas to the recipe called carbon dioxide. When heated, it expands the millions of air bubbles previously created in a batter or dough from mixing, folding and whipping trapped in the structural framework by the gluten strands. If the batter is over mixed or not baked promptly, the gas will escape and the final recipe will have poor texture and low volume.
During mixing, some air is always incorporated. Although it is usually not the major leaven, it plays an important role.
Wholemeal flour contain the entire grain which is heavier than plain flour that has its bran and grain remove, that is why the final product collapsed in the middle of the cake
Obtain frm http://www.montignac.com/en/ig_fact_modif.php & Understanding food 3rd edition by Amy Brown
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