Blanching and Freezing Vegetables

Blanching helps improve frozen food quality

blanching food

Blanching is the process of quickly exposing vegetables to either boiling water or steam for a specified amount of time, and then rapidly cooling. It is not required from a food safety standpoint; however, it will affect the quality of frozen vegetables. What does blanching do?

  • Destroys microorganisms on the surface of vegetables.
  • Softens the vegetable, brightens color, and slows the loss of vitamins.
  • Inactivates enzymes which can lead to loss of flavor, color, and texture in frozen produce.
  • Freezing does not stop enzyme activity; only blanching inactivates enzymes in vegetables.

How enzymes work in vegetables

Enzymes are large protein molecules in fruits and vegetables that promote chemical reactions, such as ripening, and can affect the quality of your product. Enzyme activity helps to speed up the breakdown of foods, which leads to the deterioration of food quality. The activity of enzymes is specific for the actual type of enzyme and is dependent on both pH and temperature. Enzyme activity affects the quality of your product and leads to a loss of nutrients and to changes in color, texture, and flavor.

Here's how to blanch vegetables

  • Use 1 gallon of boiling water per 1 pound of prepared vegetables.
  • Place vegetable in a blanching basket and lower into vigorously boiling water. Place a lid on the kettle.
  • The water should return to boiling within 1 minute. If water does not return to a boil within 1 minute, too many vegetables are being used for the amount of boiling water.
  • Begin counting blanching time as soon as water returns to a boil.
  • Keep heat on high during the indicated blanching time.

Here's how many minutes to blanch vegetables

  • Artichoke – Globe (Hearts): 7
  • Artichoke – Jerusalem: 3-5
  • Asparagus Small stalk: 2
  • Asparagus Medium stalk: 3
  • Asparagus Large stalk: 4
  • Beans (Snap, Green or Waxed): 3
  • Small Beans (Lima, Butter or Pinto): 2
  • Medium Beans: 3
  • Large Beans: 4
  • Broccoli Flowerets 1.5 inches across: 3
  • Broccoli Steamed: 5
  • Cauliflower Flowerets 1 inch across:3
  • Cauliflower Steamed: 5
  • Small Carrots: 5
  • Diced Carrots, sliced or length wise: 5
  • Celery: 3
  • Collard Greens: 3
  • All Other Greens: 2
  • Small ears corn-on-the-cob: 7
  • Medium ears corn-on-the-cob: 9
  • Large ears corn-on-the-cob: 11
  • **Whole kernel or cream style: 4
  • Edible pod peas: 2-3
  • Field peas (black-eyed): 2
  • Green peas:1.5-2.5

Read Extension's Guide to Freezing Food and watch this short video on the supplies you'll need for freezing foods.