Blanching (scalding vegetables in boiling or steam for a short time) is a must for all vegetables to be frozen. Blanching cleanses the surface of dirt and organisms, brightens the color and helps retard loss of vitamins. It also wilts or softens vegetables and makes them easier to pack.
What is Blanching?
Foods such as fruits and vegetables contain enzymes that dictate color and flavor changes. The activity of enzymes is temperature dependent. This activity can be destroyed at boiling temperatures but still be active at extremely cold temperatures. For vegetables, blanching for a brief amount of time will inactivate these enzymes and result in a higher quality food.
Vegetables, in particular, are heat blanched with water or steam. Blanching will also destroy surface microorganisms. The food will also shrink slightly for increased freezer storage. The length of time and blanching method depends on the vegetable.
Blanch Before Packaging
Blanch vegetables before freezing to slow or stop the action of enzymes. until vegetables are ready to pick, enzymes help them grow and mature. after that they cause loss of flavor and color. If vegetables are not heated thoroughly, the enzymes continue to be active during frozen storage. The vegetables will develop off flavors in a few months and may discolor or toughen. Heating also wilts or softens vegetables and makes them easier to pack. Heating for too long will result in a softening of the texture, and an unnecessary loss of water-soluble vitamins and minerals.
Blanching in Boiling Water
For home freezing the best way to heat most vegetables is in boiling water. Use a large kettle that can be covered and into which a fine-mesh wire basket fits; or use a blancher which has a blanching basket and cover. A large, loose cheesecloth bag may be used in place of the wire basket in the kettle. For each pound of prepared vegetables, use at least 1 gallon of boiling water in the blancher or kettle. Put vegetables in blanching basket, cheesecloth bag or wire basket and lower into boiling water. Place cover on blancher or kettle and keep covered during the entire heating period. Keep the heat on high so that the water will continue boiling vigorously. Start timing the heating period as soon as the vegetables are placed into the boiling water. Each vegetable requires a different heating time. Follow exactly the time recommended for each vegetable.