Freezing vegetables: what works and what does not

Freezing is the simplest way to preserve garden vegetables — and the gentlest as far as vitamins are concerned. Done properly, frozen vegetables keep for eight to twelve months and taste closer to fresh than anything else you can do.

The difference between „tastes like fresh" and „mushy and bland" comes down to two things: blanching, and how fast it freezes. Both are quickly explained.

In short

Almost all vegetables should be blanched before freezing — it stops enzymes that would otherwise carry on working.
Freeze only genuinely fresh, sound produce. Cold does not improve anything.
Freeze fast and pack in portions, with as little air as possible.
Watery types such as cucumber, lettuce, radish and raw tomato are not suitable.
Label with contents and date — after four months everything looks the same.

Why blanch?

Every vegetable contains enzymes that break down colour, flavour and vitamins. Cold slows them but does not stop them. Without blanching, a frozen bean turns strawy and bitter within months, and broccoli loses colour and aroma.

Blanching means: briefly into vigorously boiling water, then straight into iced water. The heat destroys the enzymes, the cold water stops the cooking so the vegetable stays firm. It also kills germs and preserves colour — beans and peas actually come out brighter.

How to blanch properly

Prepare: wash, trim and cut to the size you will later cook with.
Bring plenty of water to a rolling boil. Add the vegetables in batches so the water does not cool down.
Keep to the times (counted from the water returning to the boil): peas and leaf spinach 1 to 2 minutes, broccoli and cauliflower florets 2 to 3, dwarf beans 3, carrot slices 3, kohlrabi cubes 3, Brussels sprouts 4 to 5.
Straight into iced water for the same length of time. Without ice it will not get cold enough.
Drain well and pat dry. Clinging water turns into ice crystals and makes the vegetables mushy on thawing.
Pre-freeze: spread on a tray for an hour, then bag it up. Nothing sticks together and you can take out portions.

What freezes well

Very good: peas, dwarf and runner beans, broccoli, cauliflower, Brussels sprouts, kohlrabi, carrots, chard, spinach, kale, peppers (raw, no blanching), sweetcorn.
Good but softer: courgette (sliced, blanched), squash (raw cubes or as purée), leek, celery, fennel.
Only processed: tomatoes as passata or purée; whole tomatoes can be frozen raw but are then only good for sauces.
Herbs: chopped into ice cube trays with a little water or oil. Parsley, chives, dill and basil work very well this way.

What is better left out of the freezer

Lettuce, cucumber, radish, mooli: too much water, too little structure. What is left after thawing is mush.
Raw potatoes: they turn sweet and mealy grey. Cooked or as finished mash it works.
Onions in quantity: they lose all bite. In small portions for soups and sauces they are practical though.
Fresh tomatoes for salad: the cell structure does not survive it.

Tip

Freeze in the portion size you actually cook. Thawed vegetables should not be refrozen, and a kilo block of beans for two people is impractical. 200 to 400 g per bag has proven right.

Storage times and thawing

Shelf life at −18 °C: beans, peas and brassicas 10 to 12 months, carrots and kohlrabi 10 to 12, spinach and chard 8 to 10, peppers and courgette 6 to 8, herbs 6.
Do not thaw: blanched vegetables go straight from frozen into the pan or pot. They cook faster than fresh — cut cooking times by about a third.
Exception: thaw herbs and tomato sauces in the fridge.
Label: contents, quantity and date. After six months every bag is a surprise parcel.

Caution

Never put large amounts of warm or unchilled food into the freezer at once. The temperature rises throughout the appliance, everything thaws slightly and refreezes — which costs quality in everything already stored. Chill first and load in small batches.

Frequently asked questions

Do I really always have to blanch?

For storage beyond two to three months, yes. Peppers and herbs are the practical exceptions — with them enzyme breakdown is slow enough.

Why are my vegetables mushy after thawing?

Usually frozen too slowly or packed too wet. Large ice crystals destroy cell walls. Pre-freezing on a tray and patting dry solves it.

Can I still eat vegetables with freezer burn?

Yes, it is harmless, but it tastes dry and bland. Freezer burn comes from air in the bag — pack as airtight as you can.

Which is better, freezing or bottling?

Freezing keeps more vitamins and aroma but needs permanent power and space. Bottling is independent of both and suits sauces, chutneys and acidic products better. Best is to combine the two.

If you freeze a lot, sow in successive batches — then the harvest comes in stages instead of all in one week. With beans, broccoli and kohlrabi that is easy to steer using young plants set at intervals.