Молекулярная гастрономия для креативных шеф-поваров (англ. язык) - страница 170

Молекулярная гастрономия для креативных шеф-поваров (англ. язык)

become rubbery.

Recipe

Place a box of eggs in the oven set to 65 °C.

Leave for as long as convenient (minimum 2 hours).

Use of eggs in cooking: how to stabilize mixtures of fat and water

Egg yolks contain, as well as proteins and water, a group of molecules known as phospholipids and

more precisely lecithins. Phospholipids have parts in common with the most common fat molecules

(triglycerides), but one the three “tails” ( hydrophobic chains) has been replaced by a charged

phosphate group, giving the molecule both water loving (“hydrophobic”) and insoluble (“hydrophilic”)

regions.

III/I - 5 (of 9)

When the concentration in phospholipids molecules is high (in the egg yolk, it is 15%), these

molecules group themselves into little spheres, called micelles, in order to keep their hydrophobic

parts internal and protected from the surrounding watery environment of the egg yolk.

When a source of fat is mixed with egg yolks, the hydrophobic tails of the lecithin molecules will coat

oil droplets present in an emulsion, preventing them from joining together and rising to the top of the

mixture, which would otherwise cause the emulsion to separate.

The hydrophilic heads that stick out from the oil droplets, because they are charged, not only repel the

other fat droplets form contacting each other, but will be attracted to the water molecules in the water

layer, thus dispersing the surrounded fat droplets into the water part, producing...

but will be attracted to the water molecules in the water

layer, thus dispersing the surrounded fat droplets into the water part, producing stable mix of oil and

water.

As well as egg yolks, egg whites can stabilize (for some time only) mixtures of fat and water. However,

egg whites do not contain phospholipids, but they contain proteins. .

When the egg whites are whipped, the proteins contained will be denatured by shearing stress,

exposing their hydrophobic and hydrophilic regions. Since molecules containing hydrophobic and

hydrophilic regions, known as tensioactive molecules, can stabilize mixtures of fat and water, beaten

egg whites can be used to stabilize fat-water mixes.

Of course, as egg yolks also contain proteins, emulsions made from egg yolk are also stabilized by the

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