Rheological investigation of soybean protein emulsion and application to food products

Abstract

The rheological properties of a soybean protein emulsion prepared using soybean protein isolate (SPI), soybean oil, vinegar and water were investigated. The effects of altering the amount of added vinegar as well as the preparation order were examined. The results showed that when vinegar was added after the emulsification process, partly dehydrated SPI can produce a stable emulsion in which a smooth texture is maintained. Nondehydrated SPI, however, did not produce a similar emulsion from the same process. In order to determine the optimal mixing ratios of SPI, soybean oil, vinegar and water, Scheff'és simplex lattice design was adapted, and theproperties of emulsions with ten ingredient ratios were examined. The emulsions with high stability were within therange of the following mixing ratio : partly dehydrated SPI, 4-16.7%; soybean oil, 36-55%; vinegar, 5%; and water, 36-45.5 %. This emulsion showed pseudoplastic flow. In cake and mayonnaise-like emulsions, when sugar was added after making the emulsion, depending upon the amount of sugar added, the emulsion made using the ingredient ratio above had low stability and Newtonian flow. However, when sugar was added during emulsification and vinegaradded thereafter, favorable stability was achieved. Overall, altering the ingredient order was found to influence the physiological texture of the final emulsions and/or foods.