Influence of ohmic heating on commercial peroxidase and sugarcane juice peroxidase inactivation

Different fractions of sugarcane juice (liquid, solid and concentrated) were ohmically (75 °C and 7.8 V/cm for 25 min) treated to investigate the effect of different sample compounds on peroxidase inactivation. Moreover, commercial peroxidase solutions with and without the addition of sucrose were evaluated during ohmic (OH) and conventional heating (CH – with the same parameters of OH but without electric field application). It was observed that samples ohmically treated presented greater enzymatic inactivation (78% in the liquid fraction and 100% in the solid fraction, after 25 min of treatment) than those treated by CH (72% and 95% for liquid and solid fraction, respectively). The solid fraction was the most labile, and the liquid the most resistant fraction during both heating treatments. The concentrated fraction, which contains all isozymes, presented an intermediate inactivation rate. A zymogram showed three POD isozymes in the fresh sugarcane juice, explaining the different stabilities of the assayed fractions. Furthermore, the presence of sugar promoted a stabilizing effect on enzyme structure when exposed to the electric field, delaying its denaturation.