Blanch Before You Freeze, A How-To
By: Pamela Redwine
MSU Extension Service
I often get calls from clients wanting to know if they really have to blanch produce before they freeze them. Many people don’t understand what blanching is and why it is important. Blanching (scalding vegetables in boiling water or steam for a short time) is a must for almost all vegetables to be frozen. It stops enzyme actions, which can cause loss of flavor, color and texture.
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.
Blanching time is crucial and varies with the vegetable and size. Under blanching stimulates the activity of enzymes and is worse than no blanching. Over blanching causes loss of flavor, color, vitamins and minerals.
For home freezing, the most satisfactory way to heat all vegetables is in boiling water. Use a blancher, which has a blanching basket and cover, or fit a wire basket into a large pot with a lid.
Use one-gallon water per pound of prepared vegetables. Put the vegetable in a blanching basket and lower into vigorously boiling water. Place a lid on the blancher. The water should return to boiling within 1 minute, or you are using too much vegetable for the amount of boiling water. Start counting blanching time as soon as the water returns to a boil. Keep heat high for the time given in the directions for the vegetable you are freezing.
Heating in steam is recommended for a few vegetables. For broccoli, pumpkin, sweet potatoes and winter squash, both steaming and boiling are satisfactory methods. Steam blanching takes about 11/2 times longer than water blanching.
To steam, use a pot with a tight lid and a basket that holds the food at least three inches above the bottom of the pot. Put an inch or two of water in the pot and bring the water to a boil.
Put the vegetables in the basket in a single layer so that steam reaches all parts quickly. Cover the pot and keep heat high. Start counting steaming time as soon as the lid is on.
Microwave blanching may not be effective, since research shows that some enzymes may not be inactivated. This could result in off-flavors and loss of texture and color. Those choosing to run the risk of low quality vegetables by microwave blanching should be sure to work in small quantities, using the directions for their specific microwave oven. Microwave blanching will not save time or energy.
As soon as blanching is complete, vegetables should be cooled quickly and thoroughly to stop the cooking process. To cool, plunge the basket of vegetables immediately into a large quantity of cold water, 60ºF or below. Change water frequently or use cold running water or ice water. If ice is used, about one pound of ice for each pound of vegetable is needed. Cooling vegetables should take the same amount of time as blanching.
Drain vegetables thoroughly after cooling. Extra moisture can cause a loss of quality when vegetables are frozen.
· Artichoke Globe (hearts) 7 minutes
· Artichoke – Jerusalem 3-5 minutes
o Small stalk 2 minutes
o Medium stalk 3 minutes
o Large stalk 4 minutes
· Beans – Snap, Green or Wax 3 minutes
· Beans – Lima, butter or pinto
o Small 2 minutes
o Medium 3 minutes
o Large 4 minutes
· Broccoli (steamed) 5 minutes
o Small 5 minutes
o Diced, sliced or lengthwise
strips 2 minutes
· Cauliflower 3 minutes
· Corn on the cob small 7 minutes, medium 9 minutes, and Large ears 11 minutes
· Whole kernel or Cream style corn (ears blanched before cutting corn from cob 4 minutes)
· Eggplant 4 minute
· Greens – collards 3 minutes
· Okra – small pods 3 minutes, large pods 4 minutes
· Peas-field (blackeye) 2 minutes
· Summer Squash 3 minutes