Freezing food: everything you need to know

Freezing food: everything you need to know

Ever taken something out of the freezer only to find it has freezer burn? Or defrosted frozen veg and they turn to mush? Many people think you can just chuck anything in the freezer and it will be fine. There are, however, some need-to-knows that will keep your frozen food fresher, tastier and retain its nutrients for longer, without the burn.

In this blog, you will learn:

  • A brief history of freezing food
  • Does freezing food kill the nutrients and/or bacteria in food?
  • The optimum temperature for freezing food
  • What causes freezer burn?
  • What foods freeze well and how long will they stay good?
  • What food doesn’t freeze well?
  • Basic freezing techniques to retain the flavour, texture and nutrient content of the food
Frozen veg

A brief history of freezing food

As far back as 1000BC and probably longer, people living in sub-zero environments have been using freezing to preserve food. It wasn’t, however, until Clarence Birdseye made a key discovery that frozen food became the everyday trend that we know today. You may recognise his name from a well-known frozen food brand.

The modern-day ice king of frozen foods, Mr Birdseye used to work up in Canada fur trapping and noticed that his Inuit contemporaries would allow the fish they caught to freeze up immediately after being caught. And that their flavour and consistency remained intact when thawed.

The secret was the speed at which they froze, amongst other things. He patented this discovery and frozen food took off.

Does freezing food kill the nutrients and/or bacteria in food?

 In short, no and no.

Freezing food, if done properly, maintains the vitamin and mineral content and doesn’t change the nutrients in food, if used within its shelf-life.

Freezing does make microbes, bacteria, yeasts and moulds inactive, but as soon as food defrosts and reaches a temperature of 4.5ºC (40ºF) or more, these become active again and start multiplying.

Frozen peas

The optimum temperature for freezing food

Temperatures of -18ºC (0ºF) or less will preserve food the longest. In fact, they will preserve food forever in terms of being safe to eat, but there is a freezer shelf life for taste and nutrients.

As Mr Birdseye so cleverly noted, when freezing food, the rate at which it freezes is important. When food freezes, water is released and forms crystals. As it does so, it expands and ruptures the cell walls of the product. If this happens fast, the crystals will be smaller and do less damage to the cell walls, which will allow the consistency and structure of the food to stay more or less intact. If it happens slowly, the crystals will be large, obliterate the cell walls and you’ll have a very mushy tomato.

What causes freezer burn?

If food is not in an airtight container when freezing, the crystals that form escape and oxygen takes their place. This leads to dehydration and bleaching of the food and causes it to ‘burn’. You can still eat it, but it will not taste very nice as it’ll lose its colour, texture and flavour.

Frozen veg

What foods freeze well and how long will they stay good?

Most foods can be frozen.

The caveat is that vegetables need to be blanched to preserve their colour, quality and nutritional value.

What is blanching, you ask? Blanching is putting your veg in boiling water for a short period and then submerging it in ice water. What this does is inactivate the enzymes that cause it to get discoloured, so when you take out your frozen greens, they are still green.

Freezing a cake (uniced) is a great idea too, so that next time you have a party, you’ve got one on hand. Defrost in the fridge and then make a warm fudge to pour over and voila!

Freezing food chart
Cick on image to view in PDF

What foods don't freeze well?

You can’t freeze canned foods, carbonated beverages or eggs in their shells.

Be careful freezing liquid as it expands when it freezes, so make sure there is enough extra space in the container. This is why if you forget a wine bottle in the freezer, it pushes the cork up and seeps out.

Avoid freezing:

  • Cottage cheese, sour cream, cooked eggs, yoghurt and mayo – their texture won’t be great.
  • Crumb toppings – they will get soggy.
  • Fried foods – they can go rancid.
  • Home-stuffed whole poultry on the carcass – it can become contaminated.
  • Lettuce, cabbage, radishes, green onions, celery – they’ll turn mushy.
  • Cream, custard, and meringue filings – they’ll likely separate or go watery.
  • Sauces heavy in fat – they may separate or curdle.
  • Whipping cream – it might not whip up.
Frozen veg
  • Fresh food only: freeze food at its peak moment of freshness.
  • Go deep: Place the food you’re freezing at the back of the freezer against the wall and away from the door, so it will freeze faster.
  • Blanch your veg: Blanch raw veg before freezing to maintain colour and nutrients.
  • Cool food fully: Before putting it in the freezer, make sure food is fully cooled so it doesn’t heat up the surrounding food.
  • Use an airtight container: Use a ziplock freezer bag or a Tupperware with as little space for air as possible. For solid foods, like cheese, you can wrap it in clingwrap and then in a layer of foil and that should keep it pretty airtight.
  • Keep the freezer full: The fuller it is, the less power it will have to use to circulate cold air. To do this, you can ¾ fill bottles of water and freeze them to take up the extra space.
  • Shut the front door: Try not to open and close your freezer too much as you don’t want the temp to rise above -18ºC.
  • Small amounts at a time: Don’t freeze your whole grocery shop at once or the freezing process will take too long and the crystals will be bigger and do more structural damage to the food.
Frozen berries

Final note: defrosting safely

There are three safe ways to defrost:

  • In the fridge – can be refrozen raw
  • In cold water – can only be refrozen after cooking
  • In the microwave – can only be refrozen after cooking

If you put food in hot water or out on the counter, the outside can raise to above 4.5ºC (40ºF) while the inside is still frozen. This is where it gets risky because bacteria will immediately begin multiplying around the outside. That’s why it’s best to defrost in the fridge at a controlled low temperature.

Defrosting in cold water is a bit faster, but you need to have the food in an airtight bag, and you need to change the water every half hour.

For microwave defrosting, you will need to cook it immediately after, as the edges will likely have started cooking or getting warm and will be at the optimum temperature for bacterial growth.

Aruna frozen food best practice

Here at Aruna Foods, our frozen meals are made, cooled, packed and frozen on the same day.

We do things like onion chopping and weighing of all the sauce ingredients ahead of time so that our time on the day of cooking is maximised for the quality of the meals to be preserved.

We have a walk-in freezer at -20ºC that freezes our meals within a couple of hours. They are then sealed in a plastic bag that keeps in the freshness.

We do not defrost and refreeze meals. We have a shelf life that starts from the day of making the food and lasts for six months. We have tested the meals a year later and they are still great, but for maximising quality, we keep it to six months. 

Final note

If you’re in the Port Elizabeth/Gqeberha area, and you want healthy, easy and delicious vegan food, we have vegan frozen meals and vegan prepared meals for you. Pop into our store at 25 Westbourne Road, order online or check your local Spar in the Eastern Cape.

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Lisa Parsons

Lisa is a content writer and strategist with experience across many platforms. She is also a personal trainer and has a keen interest in holistic health encompassing physical, mental and emotional wellness. She enjoys travel, books, puzzles, learning languages, and a buttery Chardonnay.

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