Abstract: In order to study the effect of extraction pH on gelling properties and characteristic peptide identification of pigskin gelatin, the molecular mass distribution and gelling properties of pigskin gelatin extracted under different pH conditions were studied by dodecyl sodium sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), a texture analyzer and a rheometer. Moreover, the characteristic peptides were identified by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The results showed that with a decrease in pH, the relative molecular mass of pigskin gelatin initially increased and then decreased, the gel intensity gradually declined, and the gel melting temperature and gelling temperature initial increased and then decreased. Gelatin extracted at pH 1 had the worst gelling properties. HPLC-MS/MS analysis showed that pH significantly affected the traceability of gelatin. In this study, 62, 71, 79 and 76 characteristic peptides were detected from pigskin gelatins extracted at pH 1, 3, 5 and 7, respectively. Among them, 37 characteristic peptides were common to all pigskin gelatins. Compared with our previous research, 17 characteristic peptides were found to be common to pigskin gelatins extracted under different conditions. These stable common characteristic peptides could be used as an important basis for pigskin gelatin traceability with high accuracy.

Key words: pH value; pigskin gelatin; gelling properties; high performance liquid chromatography-tandem mass spectrometry; identification of characteristic peptides