Food Preservation Methods and Guidance (2024)

The main reason we preserve food is to keep it safe before consumption. And because we want to eat satisfying food.

Here are more reasons to preserve food:

Bacterial growth – If the conditions are right – warmth, moisture and time – bacteria like Salmonella and E. coli have a field day. Preservation methods, even simple ones like refrigeration, can really reduce the likelihood of bacterial growth and food spoilage.

Quality – To be appetising, the food needs to look, smell, feel and most importantly, taste good. If it doesn’t, we look for food that ticks all these boxes. The odd bruise or dent is often harmless, but food must be in its best quality for us to want it.

Wastage – We waste a tremendous amount of food. According to a recent study by the World Wildlife Fund and British retailer Tesco, an eye-watering 2.5 billion tons of food is wasted globally.

With 2.3 billion people being moderately or severely food insecure, this wasted food can provide each person over 2,500 meals per year. That’s seven meals a day! Preserving food extends its shelf-life and can prevent it from being wasted.

Save money – Wasting food is expensive. Each time we throw away food that we didn’t get a chance to eat before the use-by date, we throw our money away.

Saving the environment – Food that we throw away ends up in landfills. When it decomposes, it produces methane gas. Food that is wasted in landfills accounts for about eight percent of global emissions.

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Refrigerating food is one of the simplest ways of keeping it safe to eat and preserving it. The low temperature in our fridges slows down bacterial growth and reduces spoilage. Chilled food can remain safe for a few days or weeks, depending on what it is.

First, ensure the fridge being used is set at the right temperature to safely chill food. This is between 1°C and 4°C. Food must be stored under 8°C by law for businesses that sell or produce food.

Food should be stored appropriately in fridges. Most domestic fridges come with compartments for fruit and veg on the lowest shelf. This is to segregate these items from other foods like meat and dairy.

Commercial kitchens and food businesses benefit from multiple refrigerators so that food can be separated to prevent cross-contamination. Attention should be paid to food labels, with foods with the nearest use-by and best-before dates placed at the front of the stock. This is known as the FIFO system – first in, first out.

Freezing conditions inhibit bacteria growth. So, storing food properly in the freezer can make it last for a long time. Years, in fact. That said, frozen emergency pizza from 2020 should probably be thrown out now.

To optimise your freezer to preserve food, ensure it’s set at the right temperature. Freezers should be set between -18°C and -22°C. Fresh, unpacked or pre-cooked foods should be stored in freezer bags or airtight containers before being put in the freezer.

Don’t freeze food after its use-by or best-before date. If its use-by has passed and you haven’t frozen it yet, bin it. And if you’ve missed the best-before date, eat it sooner rather than later.

Frozen food must be defrosted before it can be eaten. Packaged food will come with some guidance on how long it needs to thoroughly defrost. Once defrosted, you can’t refreeze it because bacteria can grow while the food item is thawing.

This method of food preservation removes oxygen from foods. The food stored in an airtight, acidic, high salt or sugar environment prevents bacteria from growing.

Canned food must be handled hygienically and be of good quality. Jars should be specifically designed for canning. This is to ensure that they will be airtight.

You need to be careful with this particular food preservation method, though. This is because the C. botulinum bacteria thrive in environments absent of oxygen. Suppose the canning process you use hasn’t been successfully tried and tested. In that case, this bacterium can start to grow and produce toxins. These toxins can lead to botulism poisoning, a rare but life-threatening condition.

Freeze-drying is a way of dehydrating food. Raw foods comprise around 80-95% water. This water can be divided into “free” and “bound” water. Free water freezes, but bound water doesn’t. When freeze-drying food, all free water and some bound water must be removed.

To freeze dry food, you must first freeze the food product under atmospheric pressure. Then comes the primary drying stage, where all frozen, free water is removed. Once this is done, the product is dried out in the secondary drying stage. This removes the remaining bound water.

Vacuum packing extends the shelf-life of certain foods by sucking out oxygen to limit the growth of microorganisms. A benefit of vacuum packing is that it also preserves food quality without adding other ingredients, as you do with canning. So, vacuum-packed food properties, such as its smell and taste, remain intact.

Again, this method must be done carefully to prevent C. botulinum from growing.

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