Asian bullfrog (Rana tigerina) skin gelatin extracted by ultrasound-assisted process: Characteristics and in-vitro cytotoxicity.

Impact of ultrasound-assisted process (UAP) on yield and characteristics of Asian bullfrog (Rana tigerina) skin gelatin was studied and the in-vitro cytotoxicity of the resulting frog skin gelatin was evaluated using CaCo-2, Raw264.7 and L929 cell lines. Different ultrasonication modes (5 min on-time with 25 min off-time (5/25) and 10 min on-time with 50 min off-times (10/50)) were implemented for different total ultrasonication times (10-60 min) during gelatin extraction at 55 °C. UAP could effectively augment yield and recovery of frog skin gelatin, compared with the typical process (without UAP). Different UAPs used affected characteristics and properties of gelatin differently. Increased total ultrasonication time increased color changes and turbidity of resulting gelatin and induced protein fragmentation, regardless of modes used. At the same total ultrasonication time, mode of 10/50 provided gelatin with higher hydroxyproline content and higher gel strength than 5/25 mode. Gelatin extracted by UAP with 10/50 mode for 60 min (FU) possessed high yield and good gel property. Gelling and melting temperatures and FTIR-spectra of FU were similar to those of gel from typical process. Based on in-vitro cytotoxicity toward different cell lines, frog skin gelatin could be used as biocompatible material, which could be safe for human consumption.