Blanching vegetables

Necessary pre-processing stem for some methods


Why blanch vegetables?

Almost all vegetables require blanching before freezing or dehydrating, with a few exceptions. Blanching is a process where food is plunged first into hot boiling water and then cooled rapidly in ice water to stop the cooking process. Blanching kills enzymes, which cause fruits and vegetables to ripen and cause undesirable changes in food flavour, colour and texture. Make sure to follow exact blanching times for each type of vegetable. Under-blanching does not destroy all the enzymes while over-blanching overcooks and reduces flavour and nutrient content. 


How to blanch vegetables 


  • Large pot with a cover (4 L water to about 500 g vegetables or 8 L for leafy greens)
  • Wire basket or cheesecloth bag 
  • Large bowl
  • Ice
  • Colander 
  1. Fill the large bowl with very cold water.
  2. Set aside. 
  3. Fill pot with 3/4 full of water and bring to a boil.
  4. Place vegetables in wire basket or tie loosely in cheesecloth bag leaving length of string for ease of handling
  5. Lower vegetables into vigorously boiling water, cover and immediately start counting blanching time. Keep heat on high so water quickly returns to a boil.
  6. Once blanching time is up, chill vegetables immediately in cold running water. If water is not cold enough add ice.
  7. Leave vegetables in cooling water for the same time used in blanching but no longer than necessary. 
  8. Drain cooled vegetables thoroughly and freeze or dehydrate according to the instructions on each page.

Blanching instructions





Remove tough ends. Cut in uniform lengths

Med – 3 min

Lrg – 4 min

Beans (green/wax)

Trim ends. Leave whole or cut in 3 cm pieces

Cut – 3 min

Whole – 4 min


Leave root ends on; cut off tops leaving 3 cm stems. Cook in boiling water until tender. Cool. Peel and slice



Remove woody stems and trim. Cut through stalks so that pieces are not more than 3 cm across

Med – 3 min

Lrg – 4 min

Brussel Sprouts

Trim stems and outer leaves

Sm – 3 min

Med – 4 min

Lrg – 5 min


Trim outer leaves and core. Cut in wedges or shred coarsely

Wedges – 2 min

Shredded – 1 min


Remove tops and scrape or peel. Leave small carrots whole. Cut larger carrots in 1 cm slices or dice or cut lengthwise in fingers

Cut – 3 min

Whole – 5 min


Break heads into small flowerets about 3 cm in diameter

3 min

Corn – whole kernel

- on cob

Remove husks and silk

Remover husks, trim cobs to even lengths

4 min

Sm – 7 min

Med – 9 min

Lrg – 11 min





Slice. Sauté 500 ml in 30 ml butter 4 min



Remove outer skin, root and stem ends. Chop



Remove stem and root ends. Peel. Cut in 2 cm fingers or 1 cm slices

Fingers – 1 min

Slices – 1 min



2 min


Leave whole or remove seeds and half stems, cut in half or chop



Cut or break apart, remove seeds and fibers. Cut in chunks. Steam, boil or bake until tender. Cool and scoop from rind. Mash or sieve


Spinach, Chard

Wash thoroughly. Cut chard in 3 cm pieces or separate leafy parts from stalks and cut stalks in 10 cm lengths

2 min

Summer squash

 Cut in 1 cm slices

2 min

Winter squash

Cut in pieces and steam, boil or bake until tender. Cool, scoop from rind and mash

Peel and dice (butternut)



2 min


Peel by dipping in boiling water for 30 – 60 seconds, cooling in cold water and gently slipping off skin. Cut in quarters. Add 5 ml salt, dash pepper and 5 ml sugar to 1 kg tomatoes and cook gently until tender (5-6 mins)



Peel, dice and boil until tender. Mash

Peel, dice and blanch


2 min

Ref: Ontario Ministry of Agriculture and Food. (1990). Freezing Foods. Food Advisory Services. Canada Department of Agriculture.