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Blanching Vegetables is a Must Before Freezing

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Posted: June 29, 2012

If you hope to pull tasty, nutritious vegetables from your freezer next winter, you need to blanch them first.

Blanching stops the action of enzymes. These naturally occur in vegetables helping them grow and ripen. The enzymes continue to act after harvest and will cause color, flavor, texture, and nutrient losses. Freezing slows down the action of enzymes - but does not stop them.

A good example of what happens when vegetables are not blanched before freezing was shared by a participant in a freezing class. She encouraged me to share her story. To use her words, she had a "freezer full" of green beans that she froze without blanching. When she went to use some she found them mushy and flavorless and not anything she wanted to eat or serve. All her time and efforts, expense of freezer bags and electricity for the freezer, and she had to throw the beans away!

Blanching also removes air and helps vegetables to shrink so they take up less freezer space. Plant and pesticide residues and microorganisms are removed from vegetable surfaces. Peels that need removing are loosened. Blanching will actually brighten the color of vegetables.

A pan of boiling water is the best way to blanch vegetables. Steam blanching works well for broccoli, pumpkin, sweet potatoes, and winter squash. Microwave blanching is not recommended.

It is important to follow blanching directions precisely. Timing is crucial. Over blanching will cause vegetables to start cooking and quality will be lost. Under blanching has been found to stimulate enzyme activity and is actually worse than no blanching at all.

There is no "one time fits all" for blanching. Time will vary depending on the vegetable and its size. Blanching times and steps for water and steam blanching can be found at the National Center for Home Food Preservation website.

Here are a few tips for success in blanching:

  • Use a blancher that has a basket that fits inside and cover; or fit a wire basket into a large pot with a lid.
  • Use one gallon water per pound of vegetables when water blanching.
  • Blanch vegetables in small batches. After adding vegetables to boiling water and putting lid on pot, the water should return to boil within about one minute. If it doesn't, you are using too many vegetable pieces for the amount of boiling water.
  • For water blanching start counting blanching time as soon as water returns to a boil. For steam blanching begin counting time as soon as lid is on pot.
  • Cool blanched vegetables quickly to stop cooking. Plunge the basket into very cold water and change the water frequently, or use ice water. If ice is used to cool, you will need about one pound of ice per pound of vegetables.
  • Vegetables should be cool enough after about the same amount of time they were blanched.
  • Drain vegetables well after cooling since extra moisture can cause loss of quality when the vegetables are frozen.
  • Once cooled and drained, quickly move the vegetables to freezer containers and put them into the freezer.
  • As with many "rules" there is often an exception. It's okay to freeze onions, sweet and hot peppers, and raw tomatoes without blanching.

Visit the link below from the University of Nebraska-Lincoln Extension for directions on freezing onions, peppers, zucchini, raw tomatoes, and many other.