Valorisation des protéines du lactosérum: Impact de l’hydrolyse enzymatique et du traitement par Détente Instantanée Contrôlée (DIC) sur leur propriétés fonctionnelles.

Abstract

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.