Adsorption of Soy Protein Isolate in Oil‐in‐Water Emulsions: Difference Between Native and Spray Dried Isolate

Abstract The purpose of this study was to determine the differences in the emulsifying properties of isolated soy protein prepared in the pilot plant (heated and spray dried) or in the laboratory (unheated and freeze‐dried), from the same soy flakes. When the thermal transitions were measured by micro‐calorimetry, the protein isolated in the pilot plant showed a very broad thermal transition, while the native isolate showed two distinct transition peaks, attributed to β‐conglycinin and glycinin denaturation. Electrophoretic analysis and protein assay of the soluble protein in the fractions revealed a significantly smaller amount of protein recovered in the centrifugal supernatant for the isolated soy protein prepared in the pilot plant than for the native protein. A larger amount of ions was recovered in the pilot plant isolate. However, the thermal treatment of the solutions increased the recovery of the pilot plant isolate proteins in the centrifugal supernatant, with an opposite effect for the native soy protein. A significantly larger amount of pilot plant isolated protein was needed to prepare emulsions with the same characteristics of those prepared with native soy protein. The emulsions prepared with pilot plant isolates showed much lower susceptibility to heating than those prepared with native protein.