Résumé:
Whey is a by-product of the dairy industry rich in organic matter, especially lactose and
proteins with very high nutritional and functional value. This whey is the main pollutant of the
dairy industry. The milk processing industry is looking for innovative ways to convert this
pollutant effluent into high value added products. Our study aimed to improve the added value
of whey proteins as a functional ingredient either by enzymatic hydrolysis or by physical
treatment.
The first part of this work is devoted to the study of enzymatic hydrolysis effect by
proteases of plant (ficin) and animal (chicken pepsin) origin on the biological and technological
properties of whey proteins.
The results obtained showed that the degree of hydrolysis (DH) of whey proteins by
ficin is significantly higher than that of pepsin. The characterization of the hydrolysates by
FPLC and SDS-PAGE showed that ficin exhibited a very interesting proteolytic power by
completely hydrolyzing the major protein and main allergen of milk, β-Lg, a protein which is
very resistant to all types of proteases already known.
Identification of the peptides in the fraction with a molecular weight less than 3 kDa by
LC Ms/Ms showed that ficin acts more specifically on the peptide bonds of α-La than on those
of β-Lg, and that chicken pepsin acts in a narrowly specific manner on the N-terminus of the
peptide bonds of β-Lg and α-La.
The functional properties of the hydrolysates were also modified, solubility was
improved over the whole pH range compared to whey proteins with a clear improvement for
the ficin hydrolysates. The chicken pepsin hydrolysates showed an improvement in emulsifying
and foaming properties over the whole pH range, while a decrease in these properties was noted
for the ficin hydrolysates.
Enzymatic hydrolysis significantly improved the antioxidant and antihypertensive
properties of whey proteins. Fractions below 3 kDa showed the best activities. Allergenicity
prediction indicated that hydrolysis significantly reduced the allergenicity of β-Lg and α-La.
The second part of this work was devoted to the study of the effect of the Instant
Controlled Release (DIC) treatment by two applications (dry and wet basis) on the proteins
structure and technological properties. The results obtained showed that the whey protein
powders textured by DIC under dry application had higher quality attributes than those obtained
by wet DIC. The treated proteins exhibited better foam stability, water and oil absorption
capacity and decreased solubility, foaming and emulsifying power.
