Effect of Spray Drying Inlet Temperature on the Emulsifying Characteristics of Bigeye Tuna Skin Gelatin

In this work, we studied the effects of different spray drying inlet temperatures (130, 160 and 190 ℃) on the emulsifying characteristics of bigeye tuna skin gelatin. The emulsifying properties were evaluated by determination of creaming index and emulsion microstructure, and the interface and continuous phase of different emulsions were evaluated by measurement of surface hydrophobicity and gel strength. Furthermore, the mechanism of the influence of spray drying inlet temperature on gelatin’s emulsifying characteristics was analyzed by molecular mass distribution and Fourier transform infrared spectroscopy (FTIR). The results showed that the high-molecular-mass subunits of gelatin were excessively damaged and the integrity of the triple helix structure was reduced with increasing inlet temperature of spray drying, which resulted in exposure of more hydrophilic amino acids, thereby reducing the gel strength (851.29–676.65 g) and surface hydrophobicity (218.81–82.96). The decrease in surface hydrophobicity was not conducive to the adsorption of gelatin at the oil-water interface and the formation of a tight network structure, and the decrease in gel strength indicated that the network structure in the continuous phase of the emulsion become loose, thus resulting in an increase in droplet size and creaming index as well as a decrease in emulsion stability. It can be seen that the spray drying inlet temperature is negatively correlated with the emulsion stability, and the inlet temperature should not be too high for the preparation of emulsified fish skin gelatin by spray drying, preferably at 130 ℃.