Michigan State University Extension
Preserving Food Safely - 01600513
The best vegetables for freezing are fresh, tender and straight from the garden. The fresher the vegetables are when frozen, the more satisfactory the frozen product.
FIRST STEPS Wash vegetables thoroughly in cold water. Lift them out of the water as grit settles to the bottom of the pan.
Sort vegetables according to size for heating and packing unless they are to be cut into pieces of uniform size.
Peel, trim and cut into pieces, as directed for each vegetable.
HEATING BEFORE PACKING An important step in preparing vegetables for freezing is heating or "blanching" before packing. Practically all vegetables, except green peppers, maintain better quality in frozen storage if blanched before packing.
The reason for blanching vegetables before freezing is that it stops the action of enzymes. Up until the time vegetables are ready to pick, enzymes help them grow and mature. After that they cause overripening, loss of flavor and color changes. If vegetables are not sufficiently blanched, the enzymes continue to be active during frozen storage. The vegetables may develop off-flavors, discolor, or toughen so that they may be unappetizing after a few weeks of freezer storage.
Blanching also wilts and softens vegetables which makes them easier to pack. Blanching time varies with the vegetable and size of pieces.
To blanch For home freezing, the most satisfactory way to blanch blanch vegetables is in boiling water. A blancher, which has a blanching basket and cover will make the job easy. A wire basket fitted into a large kettle (and lid) will substitute for a blancher.
For each pound of prepared vegetables, use at least 1 gallon of boiling water in the blancher or kettle. Put vegetables in a blanching basket or wire basket and lower it into the boiling water. A wire cover for the basket can be used to keep the vegetables down in the boiling water.
Put the lid on the blancher or kettle and start counting blanching time immediately. Keep heat high for time given in directions for vegetable you are freezing.
COOLING After vegetables are heated they should be cooled quickly and thoroughly to stop the cooking.
To cool blanched vegetables, plunge the basket of vegetables immediately into a large quantity of ice cold water. Change water frequently so that is stays ice cold. It will take about as long to cool the food as it did to blanch it. When the vegetable is cool, remove it from the water and drain thoroughly.