While many foods can be frozen to increase their shelf life, there are some that rapidly deteriorate after a spell in the icy freezer. Here are five of them.
Some iced cakes
Claire Melvin, who runs the cake company Claire’s Handmade Cakes, told us that the issue of freezing iced cakes isn’t exactly clear cut. “It is possible to freeze iced cakes, but not really advisable,” she told us. While some small iced cakes can be carefully frozen, she doesn’t recommend freezing whole iced cakes. “Whilst the icing is defrosting, it will become very sticky.
You may also find that it grazes or cracks. If it happens to be a warm day, you could end up with condensation on top of the cake and also air bubbles popping under the icing…if you really want to freeze a cake,” she says, “freeze it un-iced”.
As well as the cracking, Claire adds that cakes iced with coloured icing can run into an “unsightly mess” on defrosting.
[See also: Why we should keep sell by dates]
Fruit and vegetables with high water content
Ever defrosted a packet of frozen summer fruits, only to find the strawberries have turned to mush? Food science blogger Alex Lathbridge, of the Procrastibaking blog, told us why. "Fruits and vegetables (such as strawberries, lettuce, cucumber and tomatoes) are made up of cells which give them their structure. These cells contain a large amount of water which, when frozen slowly, forms ice crystals much larger than the original water molecules due to the rigidity of ice's crystal lattice structure. These ice crystals cause the walls of the cells to rupture, leading to a loss of structural integrity which is cause for the mushiness witnessed in fruits and vegetables when thawed.”
According to Alex, when the cells rupture, enzymes are also released, which can result in a loss of flavour and the foods turning brown when defrosted. Tomatoes however, can be cooked into sauces and soups, for example, and then frozen.
Eggs in shells and mayonnaise
Eggs aren’t the world’s most successful freezer food. If you freeze raw eggs in their shells, the shells will crack and burst and you’ll have egg all over your freezer. If you freeze hard-boiled eggs they’ll go rubbery.
And you should never freeze mayonnaise. Richard Kempsey, Farms Director at Clarence Court, explains: “Mayonnaise is an oil in water emulsion of olive or corn oil (for example) with broken out egg. A natural part of egg yolk- Lecithin, which is a surfactant emulsifier, greatly helps the formation of good mayonnaise - it forms a stable emulsion.
On thawing mayonnaise after putting it in a freezer the emulsion breaks down leaving a rather soupy mess!” Richard recommends making up mayonnaise from fresh oil and eggs and using immediately. But if you’ve used egg yolks to make fresh pasta or custard, don’t throw away the whites. Freeze egg whites in a clearly labelled freezer bag and – great for making meringues.
Non-vacuum packed ready to eat (cooked) fish
Fish goes off quickly and it’s tempting to sling a packet into the freezer for another day. But according to Sue Lucas, who co-runs Passionate About Fish Ltd and has spent all her working life in the seafood industry, this isn’t always the best move.
While vacuum-packed ready to eat (cooked) fish can be frozen as it is, if the packaging contains air (as in the ‘over wrapped’ plastic trays covered with cling film), freezing can make the fish go soggy.
Sue told us, “If the ready-to-eat fish is loose or over wrapped, it can’t really be frozen, as the fish absorbs moisture which will create poor quality after defrosting.” But if your ready-to-eat fish is in a vacuum or ‘skin’ pack you can happily freeze it for up to 3 months.
While double cream can be frozen either as it is, or whipped, single cream turns into a gloopy, split mixture after being frozen. Christine Thompson, of The Dishy Cookery School advises: “the higher the fat content, the better it freezes…. The best way to freeze single cream is to make a sauce with it and then freeze it.
If you’re making sweet or savoury dishes with cream it is best to use double or whipping cream as these freeze well if whisked first – hence why ice cream recipes use thicker creams.” A nutrition scientist from The Dairy Council confirmed: “Single, soured, extra thick double and Channel Island creams are not suitable for freezing.”