Effect of pretreatment-assisted extraction on the physicochemical and structural properties of Rhinobatos cemiculus skin gelatin

Different pretreatment methods were applied on Rhinobatos cemiculus skin, and their effect on the physicochemical properties of the extracted gelatin was investigated. Prior to extracting gelatin, the skin was pretreated using three methods: bleaching (RCG-BT), ultrasound (RCG-UST) and microwave (RCG-MT). The properties of the resulting gelatins were compared to those of the untreated-skin gelatin (RCG-WT). The pretreatment of R. cemiculus skin was found to differently affect the isoelectric point (pH(i)), color, structure, thermal stability as well as foam/emulsion-forming capacities of the derived gelatins. In fact, the SDS-PAGE profile revealed the presence of the three gelatin characteristic chains (beta and alpha(1)/alpha(2)) as predominant components in all gelatins with a slight decrease in bands intensity for gelatin exposed to microwave radiation. Based on FTIR analysis, gelatin characteristic bands were found in all gelatins with a slight shift for RCG-MT proving its structural re-arrangements confirmed by X-ray diffraction. Furthermore, among the applied pretreatments on RCG, ultrasound and bleaching were found to be the best techniques giving the most thermally stable gelatins. Additionally, functional properties related to gelatin derived from ultrasound pretreated skin were found to exhibit the highest foam expansion and emulsion activity.