Estimation of thermostability and regeneration of peroxidase activity in orange extracts (Citrus spp.)

Abstract

Soluble and ionical-bound Peroxidase (EC 1.11.1.7) was extracted from orange cultivars Citrus sinensis (L.) Osbeck and Citrus aurantium (Rutaceae). Oranges were washed with distilled water and cut into small pieces for extract preparation; they were then homogenized with sodium phosphate buffer 100mM and pH 6.0, by a liquidizer. Afterwards, the extract underwent heat treatment at 70ºC, 75ºC and 80ºC, and the peroxidase activity measured at 1 to 10 minutes. Whereas fractions with soluble peroxidase in both cultivars were more heat stable, those with ionical-bound peroxidase were less heat-stable. Total inactivation was not achieved with the heat treatments used. A regeneration of 15% of the initial activity was observed for fractions with soluble peroxidase. No regeneration was observed in the ionical-bound peroxidase fraction. This seems to show that regeneration may be linked to different isoenzymes with different heat stability