Angiotensin I-converting enzyme (ACE) inhibitory activity and structural properties of oven- and freeze-dried protein hydrolysate from fresh water fish (Cirrhinus mrigala)

•Molecular weight of peptides were higher in oven dried hydrolysates.•The ACE inhibitory activity of peptides were not affected by oven drying.•Secondary structure of peptides were altered by oven drying.•The oven dried protein hydrolysates were stable for sequential digestion with pepsin and pancreatin.

The angiotensin I-converting enzyme (ACE) inhibitory activity and structural properties of oven-dried (OD-FPH) and freeze-dried (FD-FPH) protein hydrolysates derived from fresh water fish (Cirrhinus mrigala) muscle, using papain, were investigated. Amino acid profiles indicated a higher proportion of hydrophobic residues in OD-FPH and hydrophilic residues in FD-FPH samples. Fourier transform infrared (FT-IR) spectra revealed random coil structure in OD-FPH and β-sheet in FD-FPH samples. The approximate molecular weight of peptides in OD-FPH and FD-FPH was in the range of 7030–339 Da. The IC50 values for ACE inhibition by OD-FPH and FD-FPH samples were found to be 1.15 and 1.53 mg of protein ml−1, respectively. The ACE-inhibitory activity of OD-FPH was more stable (during sequential digestion, using pepsin and pancreatin) than that of FD-FPH sample. The study suggested that the ACE inhibitory activity of protein hydrolysate was not affected by oven-drying.