Evaluation of radish (Raphanus sativus L.) peroxidase activity after high-pressure treatment with carbon dioxide

Abstract The objective of this work was to assess the influence of compressed CO 2 on the specific activity of peroxidase (POD) from radish ( Raphanus sativus L.). The protein concentrate, in phosphate buffer, was obtained through the precipitation of proteins with (NH 4 ) 2 SO 4 . The peroxidase activity was determined using guaiacol as substrate. A semi-factorial experimental design was adopted to evaluate the effects of temperature (30–50 °C), exposure time (1–6 h), carbon dioxide density ( ρ R  = 0.6–1.8, resulting in pressures from 70.5 to 254.4 bar), and depressurization rate (10–200 kg/m 3 /min) on the peroxidase activity. Samples of lyophilized proteic concentrate were also submitted to high pressure and the effect of water content on the enzymatic activity in compressed CO 2 was studied. The water content in lyophilized samples was determined by thermo-gravimetric analysis. The results showed that the treatment of the enzymatic concentrate with CO 2 at high pressure could be a promising route to increase the POD activity.