The inactivation and regeneration of peroxidase in relation to the high temperature–short time processing of vegetables

Abstract

SummaryAs a result of the high thermal stability of peroxidase and its association with quality deterioration in high temperature–short time processed foods it was decided to investigate some aspects of the kinetics of inactivation of two purified grades of horseradish peroxidase.The following main conclusions were drawn:(a) It was shown that regeneration of peroxidase activity took place after partial inactivation at either 70, 90 or 110°C and that the first order plots of regenerated activity were biphasic in each case. Both fast and slow rates of regeneration increased on increasing the holding temperature from 30 to 40°C but no regeneration at all was observed at a temperature of 50°C. It was found that holding for 24 hr at 50°C almost completely prevented regeneration of peroxidase activity on further cooling. The extent of regeneration was found to be governed by the length of time at the inactivation temperature and a maximum was found which coincided with the high rate period of inactivation.(b) The first order plots of peroxidase inactivation were biphasic. Although the different purities of peroxidase did not give significantly different D121.1°C and z values for the low rate of inactivation over the temperature range 70–160°C, the presence of either pea or green bean purée significantly reduced the D121.1°C and, in the case of pea purée, increased the z value. It was also shown that the proportion of relatively stable enzyme was much lower in the presence of bean purée than in the presence of pea purée at each temperature.