Dynamic gastrointestinal digestion of tilapia (Oreochromis mossambicus) skin gelatin: changes of hydrolysate properties and dipeptidyl peptidase IV inhibitory activity

Abstract BACKGROUND It is important to study the physicochemical properties of tilapia ( Oreochromis mossambicus ) skin gelatin and the changes in dipeptidyl peptidase IV (DPP‐IV) inhibition activity during gastrointestinal digestion in order to understand and exploit the potential of tilapia as a source of DPP‐IV inhibitory peptides. RESULTS The DPP‐IV inhibition of fish‐skin gelatin increased from 9.92 ± 0.76% to 36.75 ± 0.98%, and further to 51.06 ± 1.23%, following simulated intestinal digestion for a period of 60 min. After gastric digestion, the degree of hydrolysis (DH) was 18.19 ± 0.48%, the average molecular weight (AMW) was 219 ± 7.19 kDa, the sum of charged groups was −5.08 ± 0.32, and the surface hydrophobicity of the hydrolysate was 24.81 ± 0.25. After intestinal digestion, these values changed to 27.72 ± 0.47%, 146.56 ± 8.16 kDa, −8.09 ± 0.32, and 13.04 ± 0.53, respectively. The DH and sum of charged groups exhibited positive correlations with DPP‐IV inhibition (0.94 and 0.71, respectively), but AMW showed a negative correlation (−0.96). MATLAB fit functions were applied to predict theoretical inhibition values, with the fitted equation: DPP‐IV inhibition = 2.5885 × DH ‐ 0.0983 × AMW ‐ 1.0047 × sum of charged groups + 3.5118. The test set for the multiple linear regression model demonstrated an R 2 equal to or greater than 0.8. CONCLUSION The DH, AMW, and sum of charged groups in the hydrolysate correlated with DPP‐IV inhibition, and the fitted equation predicted DPP‐IV inhibition effectively in tilapia skin gelatin. © 2024 Society of Chemical Industry.