Gelation of Sunflower Globulin Hydrolysates:  Rheological and Calorimetric Studies

Trypsin hydrolysates of sunflower globulins gel when heated. Gelation time and gel strength are exponentially related to concentration. Critical concentration is <1%. Sunflower globulins and their tryptic hydrolysis products have a high thermal stability, compared to most plant proteins, that is slightly affected by pH in the range 6−11. Activation energies for heat denaturation are estimated as 443 ± 9 and 423 ± 22 kJ/mol·K for the globulins and their hydrolysates, respectively. The temperature dependence of the gelation rate follows the Arrhenius law. The activation energy of gelation has been estimated as 315 ± 17 kJ/mol·K. Gelation can take place at about 20 °C below T d, but isothermal gelation experiments (at 5% hydrolysate concentration) reveal that at gelation times a fraction in the range of 15−30% of the total hydrolysate has already been denatured. This fraction becomes greater with decreasing hydrolysate concentration.