Effect of Different Blanching Treatments on the Inactivation of
Catalase and POD. Steam blanching resulted in nonuniformity of the
enzyme inactivation, and the inactivation time of catalase and POD during
steam blanching were consistently higher than that of hot water, acetic acid or
calcium chloride solution blanching. Therefore, steam blanching of carrots
was not investigated further and the quality loss parameters (b-carotene,
vitamin C loss) during steam blanching were not measured. The inactivation
time of catalase and POD in hot water, 0.05 N acetic acid and 0.2% calcium
chloride solution at selected temperatures are shown in Figs. 1–3. It was
observed that the inactivation time for POD was, in general, higher than
catalase irrespective of the type of blanching treatment used. Therefore, POD
was considered as an index of blanching for carrots. The inactivation time of
POD in water blanching was 7 min at 80–90C, 5 min at 95C and 4 min at
100C, respectively. Kidmose and Martens (1999) reported that POD inactivation
occurs in 4 min at 90C during hot water blanching treatment. The blanching
experiments of carrots were subsequently done according to the time of the
inactivation of the POD enzyme in water, acetic acid or calcium chloride.