Effect of Acetylation on Hardening and Softening Properties of Soybean Protein–Water Suspending Systems

Partially purified soybean β-conglycinin (7S), glycinin (11S) and acid precipitated proteins (APP) were acetylated to various degrees. A hybrid program was established; (i) a cyclic temperature test (20→90→20°C) under a constant shear rate and (ii) a cyclic shearing test (48.7→243.7→48.7sec−1) under isothermal conditions. The apparent viscosity of the soy protein suspending system (12%, wt/vol) gradually increased with an increase in acetyl content. A considerable increase in viscosity was found in the cooling period with an increase in acetyl content. Although native IIS globulin showed nearly no increase in viscosity, the highest acetylated 11S globulin showed a high viscosity, as much as that of 7S globulin and APP, in the cooling period and in the cyclic shearing test after heating. There was little variation among highly acetylated heated gels.