Blanching Vegetables for Freezing
Blanching vegetables in boiling water or steam for a short period of time before freezing is recommended for almost all vegetables. It slows down or stops the action of the enzymes which cause the vegetable to grow and mature. If vegetables are not blanched or blanched long enough, the enzymes continue to be active during storage causing off-colors, off-flavors and toughening. Blanching also cleanses the surface of dirt and bacteria, brightens the color, and helps retard vitamin loss. It is vital to quality to follow the recommended blanching time for each vegetable.
Blanch vegetables by lowering into boiling water. Use one gallon of water per pound of prepared food. Place a lid on pan and start counting time as soon as water returns to boil. Keep heat high so that water continues to boil. Check freezing guides such as the University of Missouri Extension Guide GH1503 for specific times.
Steam blanching can also be used for some vegetables such as broccoli, pumpkin, sweet potatoes, and winter squash. To steam, use a pan with a tight fitting lid and a basket that holds the food at least three inches above the water. Use one to two inches of water in the pan. Bring to a boil and leave on high throughout the process. Place the vegetables in the basket in a single layer . Cover the pan and start counting immediately.
Blanching in a microwave is not recommended.
As soon as the blanching is complete, cool vegetables quickly and thoroughly to stop the cooking process. Plunge the vegetables immediately into a large quantity of ice water. Cool them for the same amount of time as they are blanched. Drain vegetables thoroughly after cooling.