Science of Gastronomy: Desserts

The word dessert comes from a French word 'dessevir', which means 'to clear the table'.

Cakes:
The elasticity of the cake dough is due to formation of gluten fibers. The stronger the fibers the more elastic the dough. Water makes gluten  fibers strong while oil, acid, sugar decrease the strength of gluten thus making the dough less elastic. Salt can make the fibers strong (this is probably why we add a little salt while making the dough in a cake).
Cakes become soft by introducing air bubbles inside the cake. This can be done using leavening agents such as baking powder, baking soda or yeast. Baking powder and baking soda are chemical leavening agents. The differences between the two can be found here. However chemical leavening agent can change the taste and color of the cakes. In this case biological leavening agent like yeasts are used. Yeast requires the right temperature and the correct nutrient like sugar for it to rise. However yeast releases carbon very slowly while the chemical leavening agents produce the air bubbles faster. The dough produced by yeast is more elastic while that produced by chemical agents is less strong. Thus yeast is used for food like bread while chemical agents are used for items like cakes. Yeasts also leave behind a distinct flavor. Butter and eggs add on to the color and the texture of the cakes.

Why do cakes 'sink' in the center?
This is because of variations in temperature.

• temperature too low, or cooking time too short.
• frequent opening of the oven door.
• too much liquid or too little flour. Steam condenses and causes the cake to collapse in the center.
• cooling time too long.

Souffles:

Factors affecting the texture of souffles include

• the type of eggs: old eggs give larger volumes but fresh eggs give more stable foam. eggs from the fridge give firm and good quality foam.
• egg yolk: they are low in water content, so cause the foam to dry out. Also the proteins are too stable to form foam.
• beaters: Multiple tines = better foam. Also if the beater keeps moving around the vessel then the foam will be better.
• ingredients like salt, water, vinegar and sugar. Salt decreases the stability of the foam and will also cause the foam to lose moisture dry out. But may be used for taste. Sugar increases the stability of the egg white foam. However we have to add it at the right time. Too early and a longer time is needed for the foam to form, too late and the foam will be dry. Vinegar makes the foam more stable. 
• incorporation of ions.

Custard:

Protein denaturation is a process that happens when you heat proteins. Denaturation is followed by protein coagulation which leads the food to thicken. This phenomenon is used in making custards etc.