Do you have to blanch vegetables before freezing them at home?

For most vegetables, yes. TÜBER, Türkiye's national dietary guideline, recommends shock blanching fresh vegetables before freezing them: dipping them in boiling water for 2-3 minutes, then moving them into iced water for 1-2 minutes. The reason is written down too — both keeping the color and preventing possible losses of nutrients.

Does freezing not stop everything?

It does not. The principle of preservation by freezing is that water activity drops as ice crystals form from the water, and that microbial activity largely stops at low temperature. For biochemical and chemical reactions the guideline uses a different wording: these are "slowed down as much as possible".

That difference is exactly what you see in a vegetable you take out months later. Fading color and a change in taste are the sum of those reactions carrying on, however slowly. The blanching step comes in at precisely that point; a short burst of heat before freezing cuts off part of what would happen afterward.

How is shock blanching done?

After washing and chopping the vegetable you dip it into boiling water for 2-3 minutes. Then, without letting it wait, you move it into iced water; the time it stays there is 1-2 minutes. The second step is at least as important as the first, because a vegetable coming out of the water goes on cooking in its own heat, and iced water cuts that off.

Draining the water off the surface thoroughly once the vegetable comes out of the iced water is the last step. Water left on the surface sticks the pieces together as it freezes and makes it hard to separate out as much as you want later. Freezing the pieces first in a single layer on a tray and then putting them into a bag solves the same problem.

Having plenty of blanching water makes the job easier too. When a lot of vegetables go into a little water, the water stops boiling and the time stretches out; working with a small amount of vegetables in a wide pot is what makes the given time meaningful.

Packing and portioning

The guideline says several concrete things about foods to be frozen: the food must be fresh and clean; it must be packed divided into portions according to the household's daily and per-meal needs; it must be packed so that no air gets in, even if it will be used soon; and the containers must be closed and suitable for freezing. If you are freezing something liquid or purée-like, do not fill the container to the brim, as it expands while freezing.

The label is a separate item: the type of food and the date of freezing are written on foods frozen at home. The regulation on quick-frozen foods also defines the storage temperature as -18 °C and below; checking the freezer's setting once holds good for every package afterward.

Which vegetables suit this less?

Vegetables that will be eaten raw after thawing fall outside this method. Products such as cucumber or salad greens do not get their crispness back when thawed; frozen, they can be used by cooking them, but they do not go into a salad. The guideline's measure stands close to this: they should be frozen in amounts that can be thawed and used easily.

Make the decision by how you will eat the vegetable, not by its name. Anything going into a soup, a sauté or the oven is a suitable candidate for freezing; anything that will be eaten raw and crisp is not.

Trying to thaw a frozen vegetable before cooking is often unnecessary too; going straight into the pot or the pan while frozen, its texture breaks down less. That lets you keep the time you saved in preparation at the moment of cooking as well.

What can you do today?

Do not set out to freeze the whole fridge at once; start with a single vegetable you have too much of. While you set up the blanching water, get the iced water ready as well, and put both bowls on the counter at the same time. Write the type and the date on the packages, and use the oldest first.