Improving digestibility and the functional and biological properties of feathers meal through enzymatic hydrolysis

Chicken feathers are an important animal waste that represents about 7% of their weight, globally equivalent to about 4.5 million tons annually. It is estimated that 1 million tons of this waste are transformed into flour for fertilizers and animal feed. The conventional feather transformation process involves high temperature and pressure, resulting in high energy costs and operational risks. The objective of this study was to evaluate and optimize the technical viability of an enzymatic process to produce a protein hydrolysate with better functional and biological properties to be used as an alternative protein source in the feed formulation. Applying a Plackett & Burman (PB) factorial design for 5 variables (temperature, pH, water:feathers ratio, enzyme, and sodium sulphite), in combination with the use of a high-efficiency endoprotease (FoodPro® PXT from Bacillus subtilis), was possible to increase digestibility from 30% to more than 90%, using the 0.0002% Pepsin-HCL method. The hydrolysate with the highest degree of hydrolysis from the PB showed antioxidant properties much higher than that observed for non-hydrolyzed proteins. At this condition of hydrolysis (pH 8.5, enzyme concentration at 0.4%, 70°C as incubation temperature, ratio feather:water of 1:2 and 0.4% of sodium sulphite), the responses obtained for ABTS, DPPH and FRAP methods reached 625, 27 and 44 µmol TE/g, respectively, against 134, 10 and 12, respectively, for non-hydrolyzed feather meal. The molecular weight profile of the peptides in the hydrolysate of feathers was also measured by HPLC and showed an average molecular weight of 1.411 Da, with more than 98% of the total below 10.000 Da, suggesting that it can be considered hypoallergenic for animal feed. Therefore, the enzymatic hydrolysis of feathers is a promising process to increase the ever-increasing global supply of protein, especially for animal feed production; consequently, reducing the presence of these wastes in the environment.