Many times you’ll find instructions to blanch vegetables first before freezing them. If you’re wondering why this is required and how it’s done, here’s a tip sheet with information to get you started.
First, here’s an introduction:
- Vegetables are blanched by being held in boiling water or hot steam for a few minutes (resting in a mesh basket or metal colander) with the amount of time dependent upon type and size.
Why is it necessary?
- The idea is to heat them enough to halt its enzyme action without becoming fully cooked. This enzyme activity helps garden produce grow and if it isn’t stopped, the food can degrade in quality (even when frozen for many types of produce). Blanching helps preserve vitamins, texture and color and is also an effective way to remove surface dirt, hidden bugs and organisms.
Is the length of boiling or steaming time important?
- Yes, if not blanched long enough the enzyme activity can actually increase (for some) while if it’s done too long, it can strip nutrients, flavor and color. Once the vegetable has been added to the pot of boiling water, begin timing after the water begins to boil again.
Does it matter how much water to use or the size of pot?
- For best results, use one gallon of water per pound of produce and do no more than 1.5 pounds at a time. This helps ensure an even heating so some pieces aren’t over (or under) processed. Use a pot large enough to accommodate both water and produce and lid can fit on securely.
Why does produce need to be submerged in ice water after the process?
- This causes the heating/cooking process to stop as quickly as possible. The length of time to sit in ice water is usually equal to the amount of boiling or steaming time. Just as the amount of heating time matters, so does cooling time: If left too long in water, they can become soggy and water-logged; if not allowed to completely cool (too short of time), the product can turn sour.
How long should produce be chilled?
- Chill until center of the piece is no longer warm (you can test this by biting into a piece and testing with your tongue).
How long to drain produce before packing?
- Extra moisture can affect food quality once it’s frozen (forming frost and ice crystals on product), allow them to drain for a few minutes on a clean, absorbent towel or on a few sheets of paper towel to remove excess water before packing for freezer storage.
Can this be done in a microwave?
- It’s not advised since microwaves can vary so much in temperature levels and the amount of time required.
Does it matter how old or fresh produce is before blanching?
- Yes it does since blanching doesn’t actually improve the quality of the product, it simply stops the enzyme activity. So if you blanch and freeze the freshest, best quality product you can get your hands on, you’ll have the best results. If you work with older produce, the results will be a mediocre result (at best).
You’ll find more information on the process along with freezing tips on this page  (includes blanching times for specific vegetables).