Keratin hydrolysate for oral cosmetic use

A keratin hydrolysate comprising, amino acids and mineral material with contents by weight of the hydrolysate consisting of:

• aspartic acid ranging from 6% to 9%;
• threonine ranging from 4% to 6%;
• serine ranging from 10% to 15%;
• glutamic acid ranging from 9% to 14%;
• glycine ranging from 7% to 10%;
• alanine ranging from 4% to 6%;
• valine ranging from 6% to 10%;
• methionine ranging from 0.1% to 0.4%;
• isoleucine ranging from 4% to 6%;
• leucine ranging from 6% to 9%;
• phenylalanine ranging from 2% to 3%;
• lysine ranging from 1% to 3%;
• histidine ranging from 0.4% to 1%;
• arginine ranging from 5% to 8%;
• proline ranging from 9% to 14%;
• tryptophan of less than 0.1%;
• L-cystine ranging from 4% to 6%;
• cysteine of less than or equal to 0.1%;
• tyrosine ranging from 0.1% to 0.5%;
• and
• mineral material of less than 8%;
• wherein free amino acids are from 88% to 95% by weight of the total weight of the amino acids of the hydrolysate, the remainder of the amino acids of the hydrolysate being in the form of peptides having a molecular mass less than or equal to 800 Dalton, the peptides being from 5% to 12% by weight relative to the total weight of hydrolysate;
• wherein the keratin hydrolysate is a hydrolysate of poultry feathers selected from the group consisting of chicken feathers, turkey feathers, duck feathers, and mixtures thereof;
• and
• wherein the keratin hydrolysate is prepared by a method comprising at least the following steps, in this order:
• subjecting the poultry feathers to at least one chemical hydrolysis by means of an acid under conditions suitable for obtaining the keratin hydrolysate comprising from 88% to 95% by weight of free amino acids relative to the total weight of the amino acids of the hydrolysate, the remainder of the amino acids of the hydrolysate being in the form of peptides having a molecular mass less than or equal to 800 Dalton, the peptides being from 5% to 12% by weight relative to the total weight of hydrolysate;
• extracting the tyrosine from said hydrolysate;
• and
• optionally drying
• wherein the at least one chemical hydrolysis is carried out in two steps:
• a first chemical hydrolysis carried out at a temperature ranging from 60° C. to 80° C. for a period ranging from 4 to 5 hours, then
• a second chemical hydrolysis carried out at a temperature ranging from 100° C. to 115° C. for a period ranging from 5 to 7 hours, and
• wherein the two hydrolyses may be carried out without an intermediate waiting step or by staging an intermediate waiting step of between 1 hour and 7 days.