Combined thermal and high pressure effect on carrot pectinmethylesterase stability and catalytic activity

Carrot pectinmethylesterase (PME, EC 3.1.1.11) was extracted and purified using affinity chromatography. The effect of pressure and temperature on the stability and catalytic activity of carrot PME was studied for model systems as well as shredded carrots. The purified enzyme was characterized by an estimated molecular weight of 32 kDa and a pI above 9.3. At atmospheric pressure, carrot PME showed an optimal pH of 8.0 at 22.5 °C. The enzyme was rather heat labile (inactivation above 50 °C), however, it showed a notable pressure resistance (up to 600 MPa) especially at low temperatures (<40 °C). The catalytic activity of carrot PME was highly dependent on the temperature and pressure applied. In model and food systems (shredded carrots), optimal PME activity was registered at 50 °C in combination with pressures of about 300–500 MPa. Intact tissues revealed a pronounced PME activity at 60 °C at all pressures studied.