/ Food & Drink, Home & Energy

To freeze or not to freeze? Your freezer myths busted

Ever wondered what you can and can’t freeze? When we opened up the debate on Which? Conversation, you had tons of suggestions – so we investigated some common freezing myths to separate fact from fiction.

Freezing food until you’re ready to eat it is one of the best ways of cutting your grocery bills and minimising the amount of food you throw away.

But if you’ve ever questioned whether it’s safe to eat the age-old tub of leftovers you’ve found at the bottom of your freezer, you’re not alone.

Freezer myths busted

There’s plenty of advice and hearsay around – from government guidelines to your grandmother’s sworn-by methods. With the help of Which? nutritionist and food expert Shefalee Loth and microbiologists at the Food Standards Agency, we got to the bottom of some common freezing myths:

1. Freezing food kills bacteria: False. Freezing food doesn’t kill all bacteria. Some are dormant during freezing, but can multiply as food gets warmer when it’s defrosting.

2. Frozen food keeps forever: True. Food can be safely frozen indefinitely. However, the taste and texture may deteriorate over time.

3. You can’t freeze or defrost rice: False. Rice can be safely frozen and reheated, as long as it’s cooled quickly after cooking – ideally within an hour. You can reheat frozen rice in the microwave until it’s piping hot. Don’t freeze take-away rice though, as you never know how long it’s been left out at room temperature.

4. Frozen fruit and veg contain fewer nutrients than fresh: False. Nutrients start to leak out of fruit and veg as soon as it’s picked. Commercially frozen produce is often harvested and frozen within hours, helping seal vitamins inside, whereas fresh fruit and veg can spend days in storage, transport and lingering on supermarket shelves.

Our food-freezing checklist

So here’s our safe freezing and defrosting checklist to help you navigate the freezing minefield:

  • Make sure your freezer is running at -18°C or lower.
  • Freeze hot food as soon as it’s cooled, ideally one to two hours after cooking.
  • Wrap food well or keep it in air-tight containers to prevent freezer burn (where air dehydrates food, affecting its taste and appearance).
  • Never re-freeze defrosted raw meat or fish unless you cook it first.
  • Make sure food has defrosted all of the may through before you cook and eat it.
  • Defrosted food will spoil in the same way as if it were fresh – try and eat within two days.

Your freezing tips

We asked you to share your food-freezing experiences in a previous Convo, and we were flooded with useful tips and suggestions. Commenter Sue said she never throws food out:

‘Leftovers are frozen for later. I make bread in my breadmaker, then cut it in half and freeze the halves. I freeze chopped leftover herbs – coriander, parsley and dill. I don’t freeze leafy vegetables apart from spinach – they never seem to be as good.’

Gogsy27 championed air-tight bags:

‘Meat lasts for ages in air-tight bags. Suck the air out of larger bags before tying them. Frozen veg – green beans, peas etc – are great in pasta dishes. Far cheaper than buying and wasting – just put in as much as needed towards end of pasta cooking!’

Lots of commenters agreed that stews and curries can taste better after they’ve been frozen for a while. According to Tilly:

‘Anything seasoned or spiced takes on a stronger flavour when frozen. No idea why, but the frozen stuff is always stronger tasting after defrosting and cooking!’

So it seems that plenty of people freeze all sorts of meat, fish, fruit and vegetables for months, and found that it tastes just as good as the day it was frozen. But what about the food that tastes awful once it’s been defrosted? Have you found any foods that you just can’t trust to the humble freezer?

John the Bee Man says:
3 August 2012

Remembering my bacteriology days, bacteria will grow on the surface of the rice.The problem is the massive surface area presented by the thousands of grains of nutritious growth medium, meaning that bacteria can build up very quickly, doubling in numbers every twenty minutes. So rice left at room temperature for ten hours overnight could have 2 to the power of thirty (something over 1 billion) bacteria present for every single bacterium present at the start.
Best cool with water and freeze immediately unless you wish to test your immune system.


You are quoting the classic textbook error that the doubling time of bacteria is 20 minutes. The doubling time is very much dependent on the organism and the growth environment. Surface growth will be slower than in homogeneous culture because of relatively poor access to nutrients. I used to teach microbial physiology, which is not something that leads to interesting conversations at parties.

John the Bee Man says:
5 August 2012

Thanks Wavechange. We could have a very interesting chat!
I used an average figure (as you say, the textbook numbers), and realise that the factors you mention will have an effect on the numbers; but in any event the number of bacteria after 10 hours at room temperature will be extremely high. Unless, that is, the rice has been cooked for freezing and is not uncovered whilst cooling, when it will remain effectively sterile.
The real problem would lie where the rice is a left-over, and may have been stirred by utensils contaminated with foodstuffs, or even (heaven forfend) something that has been used on raw chicken or other meat. That could cause serious pathogenic contamination.

With many foodstuffs I would agree, John. The problem with rice is that it is often contaminated with a lot of bacterial endospores, probably helped by the rough surface that you mentioned earlier. These germinate after boiling and cooling. Now if you cooked the rice in the pressure cooker for 15 minutes you could sterilise it – and also produce some very nice rice pudding. 🙂

Modern poultry production methods seem to produce chicken with a Campylobacter dressing. At least there will be plenty of jobs for microbiologists for the foreseeable future.

Peter Hulse says:
4 August 2012

Kidneys freeze safely, but lose their texture, and are fit only for risotto..

how the heck can boiled water possibly freeze before tap water?
There`s something like 75 degrees C temperature difference for a start!

I think it is one of the ‘freezer myths’ that this Conversation is about. 🙂

Also, boiled water isn’t necessarily boiling water. It could be at room temperature.

Having looked this up,it seems to be referred to as the Mpemba Effect. Various explanations have been suggested but there seems to be no conclusive evidence that it actually happens.

candytfut says:
4 August 2012

The great thing about freezing meat is that it helps to tenderise it. I always freeze my meat unless I need it that day, and then when cooked, it melts in the mouth.

Once boiled water freezes at a different rate to freshly boiled water because boiling removes some of the Oxygen bubbles, so the water has different properties. This is the same reason that tea tastes better and is ‘ready’ quicker when using nearly boiling water or water that has only been boiled once; i.e. freshly boiled water. You can see the difference clearly if you put a teabag in two cups and add freshly boiled water to one and reboiled water to the other; the colour will take longer to leach into the water from the reboiled water.

Boiling water expels dissolved oxygen, carbon dioxide and nitrogen. There’s not going to be much oxygen in boiling water, whether it has been boiled once or many times. As water cools, it will gradually dissolve oxygen.

Boiling can precipitate dissolved salts, especially calcium salts, from water as can be seen from limescale in kettles etc. That seems to be a more gradual process and may account for the effect on making tea.

Davos says:
4 August 2012

You say- ‘Make sure food has defrosted all of the may through before you cook and eat it.’ I used to do this, but have often been told that this is a myth! Surely this does not apply to pre cooked food? It can take 20mins to defrost some frozen meal, plus another 25 mins in the oven. Many instructions say defrost thoroughly, but I give it an extra 10-15mins in the oven and it’s piping hot all the way through. Is this incorrect?

From the NHS Choices website:
“When reheating food, make sure it reaches a temperature of 70C for two minutes so that it is steaming hot throughout.”

The important thing is to make sure that the food is hot throughout and for safety it is worth reheating all pre-cooked food. Many take risks but food poisoning is, at best, very unpleasant.

Ask your GP or a microbiologist whether it is a myth. 🙂

Davos says:
4 August 2012

Thank you ‘wavechange’ (if you were responding to me!), but my comments focused on the statement about defrosting food. I am aware, and did say, that I cook frozen food until it is piping hot all the way through; but no harm in repeating this a few times!

Sorry Davos. I was just supporting ‘official’ advice, which some question despite knowing little about the subject.

Rob says:
5 August 2012

Freeze home made choc chip cookies and eat directly from the freezer. They’re fantastic. Don’t defrost else they’ll go soggy.

Ganderdonk says:
5 August 2012

Unmade points

1. Freezing slows chemical (biological) processes down, quite significantly for domestic purposes, but they do continue – hence the deterioration in taste and texture.

2. The (slowly) growing ice crystals in plant cells disrupt them sooner or later making them mushy.

3. Most wrappings, metals excluded, let moisture pass so the contents of the are slowly dehydrated, again affecting taste and texture, and ice forms in the freezer.

Great to have a bit of science, Ganderdonk. All I would add is that:

– good wrapping helps, but moisture will gradually be removed from food even if it is in sealed container.

– commercial blast freezing produces better results than home freezing because there is less cell disruption (the ice crystals are smaller).

Barbara says:
5 August 2012

I live with myself. Am vegetarian. About once a week, I cook a complex meal for a family of 4 and eat one portion freeze 4. That way I don’t put on weight, and always have a meal or two for unexpected guests, just adding fresh veges on the day. Get good variety, and always have food for emergency, ie if I spend too much time out enjoying life, I always have a meal at hand.

Alleycam says:
6 August 2012

Brilliant! just got the recipe for losing weight…’I cook a complex meal for a family of 4 and eat one portion freeze 4’… Going to try that one out!

John the Bee Man says:
5 August 2012

The recipe I have for sloe gin specifies sloes collected after frosts. Presumably this is because the water crystals break up the tissue of the sloe and soften it. Or is the sugar content increased somehow?
I have a question please: parsnips are much nicer after the frosts have hit them, but in the south the frosts are coming much later in the year or not at all. If they are put in the freezer (unblanched) for a day, will that have the same effect as a frost?

Greymanu says:
6 August 2012

I keep a ziplock bag in the freezer that I add peeled & sliced overripe bananas to. The frozen slices make amazing banana smoothies (with milk, vanilla essence & nutmeg) and there is no need to add ice which just waters it down. The defrosted banana slices are also great in baking and the cellular breakdown effectively pre-mashes them for you.

Joan says:
7 August 2012

If you like sloe gin – if you freeze the sloes first for a few days and then defrost them they will split and do not need to be pricked (depriving you of endless hours of fun I know!).

Catherine Banks says:
7 August 2012

My daughter loves making her own pizzas, but we use a ready made pizza sauce, there is always loads left over. Is it ok to freeze small batches to use later? I also buy fresh green pesto sauce and freezes small batches to use in wraps. Freezing in covered ice cube trays.

Catherine Banks says:
14 August 2012

Great, have already frozen in individual portions. Think I will use a covered ice cube tray in future. Will let you know how it turns out!

Caroline says:
25 August 2012

Coming in a bit lateon this string but a couple of comments based on some themes above. My Mum was great at not wasting food and using her freezer – here are two I would never have thought of:
1. If you have left over fresh tomatoes OR access to buying cheap when a glut occurs, then put them as is in a bag and freeze – useless for salads etc. but great for soups, casseroles etc, just use like canned tomatoes.
2. Tubes of tomato purée are very handy but expensive – buy large cans and freeze in ice cube trays. You can then use as much as you want, this works really well.

You asked what does not freeze well – soya milk. I need to use soya but only person in house and I travel a lot so keep ending up with half an unused carton. Tried freezing, it separates badly and I have not found a method to return it close to original state – it feels and tastes horrible.

When I’m boiling potatoes for mash I always cook extra. When the mash potatoes are cooled I use an icecream scoop to make portions to freeze. I put the portions on a baking tray lined with grease proof paper and place in the freezer. Once frozen the portions easily slide off the grease proof paper and can be wrapped in foil until needed. I don’t keep the mash in plastic freezer bags as it seems to give the mash a strange taste. I find this is really convenient for when my young son asks for beans and mash for lunch and time is short. Great time saver on those busy days.

Kathy says:
23 December 2012

Can I freeze brownies in the pan I baked them in?

Dianna Knight says:
19 August 2014

I have frozen a ready meal of chicken, with a spinach ravioli, I have defrosted it but it says not suitable for home freezing is it still safe to eat, if so why do chilled meals say this

jason says:
2 May 2015

I brought a vacumned sealed leg of lamb and froze it straight away, I have now come to defrost and cook it and noticed the label saying not suitable for home freezing. Is it still ok to eat ?

Hi Jason, thanks for the comment and hope you had an enjoyable bank holiday weekend. We reckon it’ll still be fine to eat, but it’s best to check with the place you bought it from first (just in case!).

I am surprised by that instruction, Jason. Freezing food will not make food unsafe to eat, but it it can spoil it in some way. For example, some fruit and vegetables are unsuitable for freezing, though commercial blast freezing can do a much better job. You could ask the company why they say that their legs of lamb are unsuitable for freezing.