State diagrams of soy globulins

State transitions of 7S and 11S soy globulins were studied as a function of moisture by monitoring their rheological and calorimetric properties. Smal l-amplitude oscillatory rheometry and differential scanning calorimetry (DS C) were used to characterize their denaturation and complexing reactions wi thin a temperature range of 40-200 degrees C and moisture contents of appro ximately 20%, 30%, and 40%. Major increases in rheological properties showe d that the 7S and 11S fractions with 40% moisture underwent structure formi ng reactions above 70 and 100 degrees C, respectively, while they reacted a t higher temperatures for lower moisture. DSC helped to identify the indivi dual complexing behavior of each fraction. The above, along with the inform ation from their glass transition, previously reported, allowed us to devel op state diagrams for each protein, where glassy, rubbery, entangled polyme r, reaction, and free-flow states were identified. (C) 1999 The Society of Rheology. [S0148-6055(99)01002-0].