The weight of one egg white is about 30 g. The proteins represent about 10 % (w), which is about
3 g xxxiii.
M ovalbumine = M egg prot = 45 000.
and 75 <M AA on average < 200
Hypothesis : M AA on average = 132.5
The average number of amino acid residues in a protein of ovalbumin is:
N = M ovalbumine / M AA on average = 339,62 @ 340
Ovalbumin is a protein constituted by amino acids (AA). We can calculate the length of the
protein, knowing the “length” of one AA.. Indeed, an amino acid is connected to another one by a peptid
link. By neglecting the influence of the radical, we thus know that an amino acid has the length of a
carbon-carbon link, and of a peptid connection: both of a length of the order of 1.5 angstroms.
Figure 60: Salty meringues (powder of white), with
tomato juice and Provence herbs.
59 / 63
O Figure 61: Two amino acids connected by a peptid link.
The length of an AA, on a polypeptide chain is thus of the order of 5 angstroms, is l = 5.10-10 m.
By estimate, we can assimilate an essential molecule of collagen to a chain constituted of n amino acids:
L = N*l = 1.70. 10-7 m
Proteins can have various sizes due to the properties of the radicals of each amino acid. We shall
thus estimate the two extreme shapes that a polypeptide chain can take; namely a thread for the most
developed shape and a cube of linked amino acids for the most compact shape.
In its most compact shape, such molecule would have a shape of cube whose edge is the cube
root of n. The surface of the air bubbles would be covered by such cubes.
Smin = (((L/l) 1/3)*l) 2 ;
Also, the most free shape would form a network of fibers of collagens, like a square of L. of
Smax = 1
The total surface of bubbles that can be covered by the proteins of gelatine is thus determined by
the number of structural units of collagen by the total surface considered:
Let Sm be the surface covered with the most compact shape of collagen.
Let SM be the surface covered with the less compact shape of collagen.