Valorization of chicken slaughterhouse by-products: Production and properties of chicken trachea hydrolysates using commercial proteases

Collagen is an abundant structural protein found in many organs of animals, for example skin, bones, and connective tissues. Chicken trachea is a collagen-rich fraction of chicken offal that is converted to a solid waste stream during poultry processing. Collagen hydrolysates and peptides have unique biological properties, which is potentially converted from chicken trachea and can be used as a useful functional ingredient. Fresh chicken trachea was sterilized by autoclaving at 121°C for 30 min and dried using freeze drier to obtain chicken trachea flakes (CTF). CTF had 68.56% protein with the 50% solubility at pH 6–10. The enzymatic hydrolysis of chicken trachea was performed using Alcalase®, Flavourzyme®, Protamex®, and Papain under the optimal condition of each enzyme. An improvement in solubility was observed. Chicken trachea hydrolysates (CTH) with the highest solubility were detected in samples hydrolyzed with Alcalase®, follow by Protamex®, Papain, and Flavourzyme®, respectively. Within an hour of hydrolysis, the CTH obtained from Alcalase® hydrolysis had the highest total amino acid contents. The top three amino acids found in this hydrolyzate powder were Glutamic acid (Glu), Glycine (Gly), and Aspartic acid (Asp). Moreover, this sample exhibited the greatest antioxidant and bioactive properties as shown by the highest antioxidant capacity from DPPH and FRAP assay (4.42 TEAC µMol/mg CTH and 22.48 TEAC µMol/mg CTH, respectively) and the lowest IC50 of ACE I inhibitor (0.41 mg/mL). These results suggested that Alcalase® hydrolysis provided the chicken trachea collagen hydrolyzate with unique properties that could be used in various food systems.