Abstract:

The contents of protein and its degradation products were analyzed during the natural fermentation of pork
by lactic acid bacteria. The results indicated that with the extension of fermentation time, the content of protein nitrogen
decreased, non-protein nitrogen and amino acid nitrogen increased, and peptide nitrogen showed a downward trend after
an initial increase to the maximum level (226.5 mg/100 g) during fermentation for approximately 20 days. Peptides derived
from sour meat fermentation for 20 days exhibited the highest ACE inhibitory activity in vitro. ACE inhibitory rate was
74.35%, with an IC50 value of 2.75 mg/mL. Ultrafiltration and D101 macroporous resin and gel filtration chromatography
were carried out sequentially for the purification of ACE inhibitory peptides. Fraction F3 had a strong ACE inhibitory
activity with IC50 value of 0.90 mg/mL, and the content of peptides was 86.54%. Amino acid composition analysis showed
that most significantly increased levels of amino acids after hydrolysis were observed for proline (7.08-fold) and tyrosine
(3.26-fold), and glutamic acid, histidine, aspartic acid, phenylalanine and alanine together accounted for 49.09% of the
total amino acids in peptides. Hydrophobic amino acids, aromatic amino acids and branched-chain amino acids in peptides
accounted for 39.35%, 10.69% and 13.65%, respectively. RP-HPLC showed that F3 was mainly composed of nine peaks
thus needing further purification.

Key words: pork, lactic acid fermentation, protein degradation, ACE inhibitory peptide, separation and purification