The leaves of Colocasia esculenta and Corchorus olitorius deteriorate quickly after harvest due to the loss of green color caused mainly by the activity of enzymes. Blanching, can be used to inactivate these enzymes to help slow down the loss of green color, although this may affect the nutritional quality of the leaves. In this study, the effect of hot-water blanching on the stability of chlorophyll, ascorbate, and phenols in the leaves of C. esculenta and C. olitorius was investigated. Blanching was carried out in hot-water at temperatures of 71, 82 and 93 ºC for durations of 1, 2, 3 and 5 min. The efficiency of blanching was assessed based on the inactivation of peroxidase. Blanching inactivated peroxidase with more than 90 % activity lost after 3 min of blanching C. esculenta leaves at the different temperatures. However, a 90 % inactivation of peroxidase activity in C. olitorius leaves was observed after 5 min of blanching. The total phenolic content of both leaves was not affected by blanching, however the retention of ascorbate decreased and the loss of chlorophyll increased with increasing duration of blanching. After 5 min of blanching, about 38, 34 and 15 % of ascorbate levels were retained at 71, 82 and 93 ºC respectively, in C. esculenta leaves. With the exception of blanching at 82 ºC, similar ascorbate levels were retained in the leaves of C. olitorius. Less than 15 % of chlorophyll was lost when C. esculenta leaves were blanched at 71 ºC for 2 min or less. Similar loss in chlorophyll was observed when C. olitorius leaves were blanched for 2 min or less.
The leaves of C. esculenta and C. olitorius deteriorate quickly after harvest due to degreening caused mostly by action of enzymes. Blanching can therefore be used to inactivate enzymes with the aim to enhance the quality of the leaves during storage.
Ascorbate, Chlorophyll, Hot-water blanching, Peroxidase activity