| Abstract: | Carrot slices cooked for 11 hours on the LOW setting of an electric casserole were firmer and less acceptable than those which had been boiled for 25 minutes; when slices were cooked on the HIGH setting of the casserole for 6 hours they became as soft as boiled slices. Short periods of heat treatment in the casserole on LOW, followed by boiling for 25 minutes, produced slices which were firmer and less acceptable than those which had simply been boiled. These observations may be explained in terms of the action of the enzyme pectin methylesterase (PME) which at certain temperatures can cause firming of plant tissue. During the early stages of casserole treatment on LOW, considerable PME activity could be detected in carrot slices whereas on the HIGH setting, thermal inactivation was more rapid. When using the casserole on LOW, undesirable firmness in carrot tissue could be prevented by subjecting slices 1 cm thick to a preliminary 2 minute blanch in boiling water. |
