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

The objective of this work was to assess the influence of compressed CO2 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 (NH4)(2)SO4. The peroxidase activity was determined using guaiacol as substrate. A semi-factorial experimental design was adopted to evaluate the effects of temperature (30-50 degrees C), exposure time (1-6 h), carbon dioxide density (rho(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 CO2 was studied. The water content in lyophilized samples was determined by thermogravimetric analysis. The results showed that the treatment of the enzymatic concentrate with CO2 at high pressure could be a promising route to increase the POD activity. (c) 2005 Elsevier B.V. All rights reserved.