On the contrary, no calculation can ever tell if lard is better than oil or butter, if chestnut flour is better
than rice flour, etc.
What does cooking mean?
Having shown that we do not need fixed recipes, let’s come to the main point of culinary craft: cooking.
What is cooking? Let’s consider first cooking eggs and move later to meat, fish and vegetables or
In boiling water, an egg white looses its transparency and yellow color to become white; it loses its
liquid consistency to become solid. Why?
The preliminary experiment of heating an egg white (about 30 g) in a pan shows that egg white is
made of two parts: first water, forming a white smoke over the pan, makes 90 percent of the white; in
the pan, after evaporation of water, a yellow solid sheet is primarily made of proteins (about 3 g).
As water does not coagulate, it has to be admitted that proteins are responsible for the coagulation of
egg white when heated. Why? Chemical studies have shown that proteins are like coiled open
necklaces; the pearls are amino acid residues, of which two major kinds exists: hydrophilic ones and
hydrophobic ones. In water, proteins reduce their energy by coiling so that the hydrophobic segments
of the protein are in the centre, surrounded by hydrophilic parts.
These proteins do not retain their fixed coiling, as water molecules are perturbing the coiling. When
the kinetic energy associated to heat is greater than the coiling energy, proteins uncoil, and expose
their thiol groups –SH of cystein amino acids; under oxidizing circumstances, these groups react to
form disulfide bridges (-S-S-) that link proteins together.
Figure 4. When proteins (with hydrophobic core, in red, and hydrophilic parts, in pink) uncoil,
they can link because sulphur atoms make “disulfide bridges”. Linking of proteins is
responsible of the formation of a protein network, in which water from egg whites are trapped.
In the heated egg white, linked proteins form a network where water molecules are trapped. This is
called a gel (more precisely a chemical gel, as disulfide bridges are strong forces, and chemical gels