Food Preservation Methods and Guidance

Although refrigeration is a basic storage method nowadays, it was once a luxury. Storing food at a low temperature is the simplest, and often safest, way to store many types of food, as the food you plan to chill usually requires minimal preparation – or it’s already done for you.

Fridges preserve the quality and safety of food because the cold slows bacterial growth and minimises spoilage. Depending on the type of food, it can last between a few days and a few weeks in the fridge before the texture and taste deteriorate.

To safely refrigerate food, you should:

• Set your fridge to a temperature between 1°C and 4°C. The law requires you to store food for commercial use under 8°C.
• Use separate refrigerators, where possible, for raw and high risk or ready-to-eat food to minimise cross-contamination. If it’s unpractical for you to use separate fridges, you should be aware of which fridge shelves you should store food on. For example, ready-to-eat food should sit above raw food at all times.
• Ensure you label food with best before and use by dates if you remove the original packaging.
• Avoid overloading the fridge or placing food in front of the cooling unit. Ensure there’s plenty of room between foods to allow air circulation.
• Put canned food in a separate container before you refrigerate it. When you refrigerate an open can, a small amount of metal transfers to the food which, although not harmful to consumption, gives food an unappetising taste.
• Use a FIFO food storage system to ensure you use those with the nearest best before or use by dates before others. Proper stock rotation minimises waste and saves you money.

If stored properly, frozen food can last for months. In fact, because bacteria cannot grow when frozen, food you keep in the freezer can remain safe to eat for almost indefinite periods of time. However, it will eventually deteriorate in quality and become unappetising, so you should use most frozen food within a few months or a year.

To safely freeze food, you should:

• Set the freezer to a temperature between -18°C and -22°C.
• Place food in air-tight containers or freezer bags before freezing. Proper wrapping is especially important for meat, otherwise it may get freezer burn and become inedible.
• Only freeze items before their best before or use by date.
• Never refreeze defrosted food, as it gives bacteria an opportunity to grow between thawing. You should either use it right away or store it in the fridge for up to 24 hours.
• Defrost the freezer regularly to keep it free of an ice build-up. You should be able to keep frozen food in the fridge for a couple of hours maximum while the freezer defrosts.
• Label food with the date you freeze it. You can refer back to the date to see whether you should use the food before it deteriorates. Use our online guide to check how long food lasts in the freezer.

Preserving food in a high-sugar environment stops bacterial growth by reducing the food’s water content. It works particularly well for fruit: you can make jam and marmalade that lasts for a long time, and you can use canning to store it (see the section below).

All sorts of sugary substances work well to preserve food, including sugar granules, sugar syrup, or honey. Some sugaring recipes even use alcohol alongside sugar to preserve certain foods.

You may use sugaring to preserve foods such as:

• Fruit – apples, peaches, plums, apricots, cherries, and more preserve well when sugared.
• Vegetables – ginger and carrot are commonly sugared and used for relishes or condiments.
• Certain fish and meat – you can combine sugar with salt or another liquid to make a brine that helps preserve meat and reduce saltiness.

Using an excessive amount of sugar comes with health risks, but if you reduce the amount of sugar to lower than what is necessary, you may allow the food to spoil. Make sure you follow suitable sugaring recipes shared online or in books to get the right amount, and be sure to consume sugared foods in moderation.

Similar to sugaring, salt draws water out of food and stops bacterial growth. In high concentrations, it can even destroy bacteria cells, although by this point the food is likely unappetising.

There are two forms of salting:

• Dry curing – you apply salt to the food, such as meat, and leave it to draw out the water.
• Wet curing – better known as brine, you mix salt with water and add food to the liquid to preserve it, usually together with canning (see the canning section of this guide).

As with sugar, excessive salt consumption can harm health, so you should follow suitable salting recipes found online or in published food preservation books. You also need to use salt specifically designed for pickling or a Kosher salt.

Keeping food canned significantly extends its lifespan – but only if done correctly. The canning process preserves food by removing oxygen through an airtight seal and containing food in an acidic, sugary, or salty environment, where bacteria cannot thrive.

You should follow a safe, proper canning process:

• Select good quality food that is still within its best before or use by date. Handle it hygienically.
• Purchase suitable jars and self-sealing lids specifically designed for canning. You cannot reuse old peanut butter jars and jam pots; they won’t ensure an airtight seal.
• Purchase a canning rack.
• Follow tested preservation recipes. You must follow every step carefully to make sure your canned foods preserve safely. Visit freshpreserving.com for good examples or search for books online.

Follow these canning steps:

• Heat the jars beforehand in simmering water (not boiling).
• Prepare the food according to the preservation recipe. You usually need to heat food to boiling.
• Remove jars from the water and loosely fill them with the food.
• Depending on the recipe, you may fill the jar entirely with the food (e.g. jam) or you may need to add an acidic liquid or brine, which you’ll boil beforehand.
• Leave ½ inch of headspace and apply the sealing lid. Adjust the lid until the fit is fingertip tight.
• Submerge the jars in boiling water using your canning rack for the period of time that the recipe states.
• Remove and set aside to cool for as long as stated.

It’s critical that you follow a tested canning process to increase the longevity and safety of food. If improperly canned, food containing C. botulinum may produce toxins that cause botulism poisoning: a rare but life-threatening condition. Fortunately, C. botulinum remains inactive in high-acid environments, so make sure you follow any steps that require adding acids.

Similar to canning, vacuum packing deprives bacteria of oxygen by creating an airtight atmosphere. While food may not last for as long as canned goods, vacuuming still extends its storage life for much longer than keeping food in the fridge or in a cupboard.

Vacuum packing also has value as a preservation method because it preserves the quality without the need for other ingredients (unlike canning). It usually maintains the food’s smell, colour, taste, and texture – which is particularly desirable for meat you intend to cook rare. In the absence of air, vacuum packed food also retains its moisture, which ensures optimum food quality.

Beyond preservation, vacuum packing also works well for food preparation. Many chefs vacuum pack specific ingredients and cook it at a precise temperature to produce unique results.

To safely vacuum pack food, you should:

• Prepare the food hygienically. Wash fruits and vegetables and trim unwanted skin, fat, and bone from meat.
• Place the food inside a suitable vacuum packing plastic bag.
• Feed the plastic bag into a vacuum packing machine.
• Allow the vacuum packing machine to run.
• Store in the fridge or a cool, dry place.

You can follow certain methods that don’t require a machine to vacuum pack food if you like, but they usually sacrifice food safety and produce varying results. Remember: to prevent botulism, airtight packaging must be spot on. In a commercial setting, always use suitable equipment to vacuum pack. You’ll preserve food safely and make it safe to eat at a later date.