Blanching

Blanching is a heat treatment process generally applied to fruits and vegetables prior to freesing, drying or canning.

Blanching is primarily carried out to inactivate enzymes before freezing or dehydration.

In plant tissues, enzymes such as lipoxygenase and polyphenol oxidase cause loss of nutrition, flavor and texture.

Peroxidase and catalase are two of the most heat resistant and widely distribute enzymes. Although they are not the cause of deterioration during storage, their activity is used to evaluate the effectiveness of blanching.

In commercial blanching, the blanching time in boiling water at 100C varies from 1.5 to 4 min.

The two most common method used commercial methods are passing food through atmosphere of saturated steam or bath of hot water.

The cooling stage may result greater loss of product or nutrients than blanching stage.