How To Freeze Food

Last Thursday, 21^st January, I was invited by BBC Radio Kent to be the guest on Julia George’s morning phone-in programme to discuss and answer questions on the topic “What’s in your freezer?”  I thought it would be helpful to follow up the programme with a short article dealing with the food safety issues associated with freezers and frozen foods.

The freezer is an integral part of any kitchen and allows the busy cook to plan and prepare meals well in advance of when they’re actually going to be consumed.  A well-stocked freezer can significantly cut preparation time and enable great flexibility with menu options.

Almost any type of food can be frozen, but being able to freeze food and being able to use it after defrosting are two entirely different things.  Some foods simply do not freeze well at all, e.g. eggs in shells and egg-based sauces, cream and emulsion based sauces, lettuce and soft leafed herbs.

Raw meat, poultry, game and fish definitely maintain their quality longer than their cooked counterparts because moisture retained during the freezing process is lost during cooking.

Is Frozen Food Safe?

Contrary to the popular misconception, freezing food does not kill germs, but rather will retard and inactivate any pathogenic and spoilage bacteria.  Yeasts and moulds are more likely to grow on frozen foods, however, in reality very few organisms grow below -10°C.  This is why it’s very important to maintain accurate temperature control of your freezer; ensuring that frozen foods are kept at a temperature of at least -18°C.  At temperatures below -18°C the oxidisation of food significantly slows up, which aids in the preservation of the product.

The same rules apply for foods stored in a freezer as for those stored in a fridge.  Raw frozen foods must be kept completely separate from frozen but already cooked ready-to-eat products.

Remember: If food goes into the freezer already contaminated with pathogens, once defrosted it will still be contaminated with the same harmful bacteria.  Therefore it’s absolutely essential that thawed food is then cooked to the recommended temperature of a least 75°C; this is the only way to ensure the food is safe to eat.

How Long Can I Freeze Foods For?

Most foods will keep for prolonged periods in a freezer, although a recommended ‘shelf life’ is given because of degeneration of the quality of a specific product – in terms of flavour, texture, colour and nutritional quality.  All packaged food which is purchased already frozen should be used within the date given by the manufacturer of the product.  However, as a general recommendation, vegetables, fruit and meat stored below -18°C can be safely stored for up to 12 months, and fish, sausages, butter and soft cheeses for up to 6 months.

Theoretically, you can freeze and refreeze food as many times as you wish, however, one very important point to be aware of is that refreezing will significantly diminish the quality due to the loss of moisture in the thawing process.  Although food which has been refrozen may be safe to eat, from a quality standpoint, I would never advocate refreezing food that has been defrosted.

Wrapping and Packaging

If you’re freezing food for short periods, then wrapping in Clingfilm or placing in plastic freezer bags is usually adequate.  However, when you wrap foods, make sure they’re wrapped very tightly to exclude all air.  This will reduce the risk of what is known as “freezer burn, which occurs when air comes into direct contact with frozen food.  It’s worth noting that whilst freezer burn does not necessarily make the food unsafe to eat, it does adversely affect the food in terms of quality, particularly the colour and texture of the product.  Vacuum packaging foods prior to freezing will safeguard against freezer burn and will also assists in protecting foods which are more susceptible to oxidisation.

When freezing food for longer periods, it’s a good idea to use wrapping and packaging which is more robust, such as heavy-duty freezer bags and plastic containers.  Never put glass or china in the freezer, as the extreme cold can quite easily cause it to crack or shatter, leading to physical contamination of products.  It is always best to use packaging that has specifically designed for freezer use.

Labelling

Unless you label the food you’re freezing, you might not remember what it is, let alone when it was frozen.  Always clearly label the food, stating exactly what it is, when it was frozen, and when it must be used by.  It’s advisable to use food specific colour-coded labels: blue labels for raw fish, red for raw meat and poultry, and yellow labels for cooked and ready-to-eat products. Make sure you label the food clearly and plainly, this is very important, not least because food can be tricky to identify after it’s been deep frozen for several months.

Defrosting Food

Frozen food should always be thawed prior to cooking, unless the manufacturer’s instructions on the label state otherwise.  Cooking partially thawed food, will in all probability lead to uneven cooking, which subsequently will cause harmful bacteria to survive the cooking process.  When defrosting food, especially when catering for larger numbers, always plan ahead!  It’s always best practice to thaw food such as turkeys, chickens, and joints of beef in the fridge for at least 24 hours before they are to be cooked.  It’s worth noting that large joins of meat can take anywhere between 36 and 48 hours to defrost.  When thawing raw meat and poultry, ensure they’re covered and placed in a deep container in the bottom of the fridge completely separate from other food, especially ready-to-eat food.  This will stop thawing blood or juices dripping down onto other food stored in the same fridge.  If you haven’t got the fridge space to defrost, then find some other very cool but hygienic place, as mentioned already, cold temperatures slow down the multiplication of pathogens.

Once thawed, however, microorganisms can again become active, multiplying under the right conditions to levels which can easily lead to food poisoning and foodborne illness.  Therefore, you must apply the same principles to defrosted items as you would to fresh, perishable food.