Blanching is a cooking process wherein the food substance, usually a vegetable or fruit, is plunged into boiling water, removed after a brief timed interval, and finally plunged into iced water or placed under cold running water (shocked) to halt the cooking process. This not only preserves the nutrients of the food but also maintains its crispiness and colors.
The technique of blanching vegetables is best illustrated by the requirement to stop cook asparagus otherwise it would become soggy due to the asparagus continuing to cook after it is removed from the boiling water. To cook asparagus using the blanching method, the shoots are boiled for 30 seconds, and then to stop further cooking they are dipped into cold or ice water. They come out crispy and bright green with most nutrients still intact.