Молекулярная гастрономия для креативных шеф-поваров (англ. язык) - страница 166

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

the network; at any temperature, water evaporates (this is why ponds dry at the shining sun, but even

roads are finally dry, after the rain), but if temperature is higher than 100°C, then water boils and forms

craters in egg white.

In conclusion, over-cooking an egg white therefore makes it rubbery for reasons clearly explained in

section 1.

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Water molecules being squeezed out of a tightly bonded protein network

Presence of salt

In cooking, eggs are usually salted. As well as providing a taste advantage, the Na+ and Cl- ions

present in the salt will surrounded the positively and negatively charged regions of the proteins,

neutralising them and thus reducing repulsion between similarly charged regions on neighbouring

proteins.

This causes the egg proteins to coagulate more quickly and at lower temperatures. In addition, the

proteins involved in the network can not get as close to each other as they would normally (due to the

presence of the surrounding ions) so the resulting network is also tenderer and less tough.

Presence of acid

When an acid is added to egg white, there are some effects, but not immediately. Acids are

compounds that give hydrogen ions (H+).

In the presence of these H+ ions, both denaturation and coagulation of proteins is increased because

acids increase the unwinding of the proteins, and allows them to form a network. More precisely, parts

of proteins get the same electrical charge,...

acids increase the unwinding of the proteins, and allows them to form a network. More precisely, parts

of proteins get the same electrical charge, so that they repel themselves: proteins unwind. And

unwinding gives way to coagulation.

H+ H+ H+

H+

H+

Effect of different temperatures

The coagulation of egg white proteins begins at temperatures a temperature of 62°. At higher

temperatures, as more and more proteins denaturate and contribute to the network, the consistency of

the cooked egg white is more and more firm.

More precisely, the denaturation temperatures of egg white proteins are:

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Proteins Denaturation temperature

Ovotransferrine 61°C

Ovomucoide 70°C

Lysosyme 75°C

Ovalbumine 84,5°C

For the yolk :

LDL 70°C

HDL 72°C

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