Physicochemical properties and aroma release of gelatin-stabilized rapeseed oil-in-water emulsions as affected by pH

The release of volatile compounds in food processing is inevitable, and controlling aroma release is an important means of improving flavor quality. Herein, the physical stability and aroma release of 50 wt% rapeseed oil-in-water emulsions stabilized by 1 wt% gelatin at various pH levels were investigated in this study. Results showed that the emulsion prepared at pH 10 had a lower creaming index (CI), a smaller droplet size, a higher zeta potential value, and greater elasticity than that prepared at pH 4 and 7. Isobutanol, dimethyl sulfide, dimethyl sulfoxide, dimethyl sulfone, and γ-butyrolactone were detected in rapeseed oil but not in all emulsions. When the aqueous phase pH increased, the ability of emulsions to bind hydrophobic compounds increased significantly, while its ability to bind hydrophilic compounds with a density greater than water or less than oil decreased. The enhancement of the aroma-retention ability was due to an increase in the binding area between hydrophobic odorants and oil droplets, while the decrease in the aroma-retention ability was due to the hydrophilic properties of odorants, thin protein films, and density difference. This work explained the flavor release mechanism from the perspective of the hydrophobicity and density of volatile compounds and the interfacial protein films, which can provide certain theoretical and practical values for improving the flavor quality of broth products.