Can You Freeze Glass Containers
Author: Rachel Date Posted:1 March 2023
Can I use glass for freezing food?
One question I get asked a lot is, can I use glass for freezing food?
It’s a great question. Anything we can use that is not plastic heading straight to land fill after we’ve used it once, is worth exploring.
I stopped buying and using single-use freezer bags a long time ago. Looking back now, it seems absurd to have used disposable freezer bags for all those years. But I didn’t know any better. I was unaware!
If you don’t know the reasons for quitting single-use plastic, here's a good place to start
I love my reusable freezer bags. They’re so versatile and handy for reducing plastic packaging at the butcher or local delicatessen, as well as for storing leftovers in the fridge and freezer, or even snacks and staples in the pantry.
Click here for some examples.
But reusable freezer bags aren’t the only tool you have to rely on when it comes to busting plastic waste while storing food in the freezer.
Plastic containers are an option, but not recommended. Especially with hot food, chemical components of the plastic can leach into your food, and then, inevitably, because you’re such a good cook, in someone’s belly, potentially accumulating and causing havoc with their endocrine system.
If you do use plastic tubs, make sure only room temperature liquid or food is added to the container, which should be BPA free and air tight. Avoid adding oily or fatty foods (including dairy) to plastic containers. And definitely don’t use them to heat food in the microwave, even if they say microwave safe.
So, what about glass?
Can you use glass containers to freeze food, or will they crack with the change of temperature?
The answer is – it depends.
Generally, the type of glass you use will be a deciding factor.
If your container is made from tempered glass, it will have oven safe and freezer safe symbols imprinted on the bottom. Or you could use borosilicate glass, which is lighter and tougher than normal glass and can withstand both hot and cold temperatures.
That’s not to say other glass is off the table. You just have to be discerning.
For example, storing a leftover soup in a repurposed mayonnaise jar is perfectly fine. Just ensure the contents are at room temperature before adding to the jar, and leave enough space for the contents to expand as they freeze; at least 10%. If you don’t leave enough room, then the glass could indeed break.
If you’re not sure, leave the lid slightly ajar until the food has frozen, then seal.
Repurposed mayonnaise jars are also great for storing food in the fridge or for staples in the pantry (like rice, or cookies...), helping you to reduce your use of single-use plastic!
Don’t take your glass container straight out of the oven and into the freezer, or vice versa, even if you have an oven / freezer safe glass container. Allow the food to cool down or thaw out first. For two reasons.
One, to be sure the glass isn’t affected by sudden extreme temperature changes, even if it is tempered.
And two, adding hot food to a cold freezer will mean the freezer has to work harder to cool back down to temperature, which uses energy.
The great thing about using glass for food storage is, it won’t leach anything into your food and equally, won’t stain or smell like plastic can. Even with that delicious, sloppy, tomato-y lasagne you just made.
Make sure the glass container you’re using is fit for purpose. Don’t use thin or flimsy glass.
And a word to the wise, just be sure not to try and speed your way through the thawing process with hot water or microwaving. Slow and steady wins the race. Plan ahead and pop it in the fridge overnight with the lid slightly popped, or transition from freezer to fridge to benchtop, to avoid cracking under the stress of the temperature change.
Great work, Eco Warrior!
Yes, you can use glass in the freezer, just ensure you keep to 2 simple rules:
1. Don’t put hot liquid in a cold vessel, or straight in the freezer.
2. Don’t fill! Leave space for the food to expand as it freezes.
P.S. If you can’t remember when the Bolognese sauce went in the freezer, or if that’s the hot or mild gazpacho, then you might need these neat little reusable food labels.
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