Giving Broiler Feathers a Good Fate. Optimization of Chemical Hydrolysis for the Production of a Hydrolysate Rich in Free Amino Acids

The poultry meat production chain generates considerable waste, especially feathers. Feathers, composed of low solubility, digestibility, and chemical stability keratins, pose a significant challenge for reuse. This study, however, has successfully optimized the alkaline hydrolysis process using sodium hydroxide, potassium hydroxide, and an equimolar combination under varying temperature and time conditions. The different hydrolysis conditions were statistically evaluated to identify critical optimization points. The errors between the predicted and experimentally acquired results were remarkably low, providing a high level of reliability for the process. They achieved higher protein hydrolysis rates (97.9% for NaOH, 96.7% for KOH, and 97.8% for the mixture). Analysis by ¹³C nuclear resonance (¹³C NMR) spectroscopy was conducted on both intact feather samples and obtained hydrolysates, demonstrating the efficiency of breaking down keratin into free amino acids and peptides. The merit of this study is not just in its successful demonstration of a high hydrolysis of the keratin in broiler feathers from industrial abattoirs using sodium hydroxide (a low-cost alkali) at a low concentration (2.6%) and a temperature of 75.6 °C, but also in its potential to provide a sustainable solution for the waste management and poultry meat production industries. The results show their possible applicability on an industrial scale, as the resulting optimal conditions are mild.