Freezing in Glass Jars

In a world that seems to have turned upside down over the last few weeks and months, and with many countries still in enforced lockdown, it feels a little strange to talk about even small positives coming out of this strange and uncharted experience. Of course, these are the most challenging of times for many of us, and no-one would want to make light of the situation we face, but there are some small outcomes that are worth looking at, and even celebrating.

One of those unexpected outcomes is that the nation is learning to love cooking again and is also getting into home preserves in ever-increasing numbers. Of course, we’ve seen a resurgence of interest in both of these activities in recent years, fuelled by TV programmes such as Great British Bake Off and Masterchef, but since the lockdown started, interest in all things culinary has gone through the roof.

More people than ever before are looking at both home preserving and freezing, in order to stockpile nutritious food and minimise the number of shopping trips that they need to make. In today’s blog post, we thought we’d answer one question that keeps coming up, from both newbies and seasoned home cooks - can you use glass bottles and jars to freeze food in?

Glass jars in the freezer - yes or no?

If you took a straw poll of a hundred people and asked them whether it’s possible to freeze food in glass jars, a huge number would say no, it wasn’t a good idea. If pressed, they’d likely say that the contents would expand when frozen and crack or smash the glass, leaving you with an expensive mess to clear up in your freezer.

However, the real answer to this question is...it depends! It’s not generally recommended to freeze shop-bought jars of food, as the chances are that the jars used are not the best shape for freezing and there is not enough space left in the jar for that all-important expansion to take place.

If you are thinking of freezing some home-cooked food, however, you may well be able to use some jars safely. The key here is to use wide-necked jars and to leave plenty of space at the top of the jar. Used in this way, all sorts of food can be successfully frozen, including pasta sauce, homemade passata, apple puree and so forth.

At this point, we should say that most manufacturers don’t recommend using their jars in this way, out of an abundance of caution. However, so many of our customers have told us that they use our jars for freezing, that we feel it’s worth discussing. After all, if you grew up in the 60s and 70s when the milkman delivered milk to your door in glass bottles, you’ll remember those bitingly cold winter mornings when the milk froze in the bottle on the doorstep, pushing the foil cap off the top of the bottle.

If you think back to those times, the milk bottle never broke once, did it? Provided that there is plenty of space in your jars for expansion of the contents, everything should be fine. We recommend only filling jars three-quarters full and keeping them standing up in the freezer at all times.

What about glass bottles?

Whilst we’ve just mentioned glass bottles with frozen milk in them, back in the 60s and 70s, we are less enthusiastic about using bottles to freeze things in today. Of course, everyone has at some time or another popped a bottle of white wine or beer in the freezer to chill it quickly, and that’s fine. What we don’t recommend, however, is leaving glass bottles in the freezer permanently. The reason for this is that bottles don’t generally have that wide neck that we said was important when freezing in glass jars.

With a long slender neck, a bottle will come under much more pressure when its contents expand during freezing and is therefore much more likely to crack. At a time when we are all trying to make our food go as far as possible and to minimise food waste, it’s just not worth the risk of trying out some frozen bottles.

So, to recap, if you are thinking of using glass jars to freeze some homemade food, go for sizeable jars with a big, wide neck. Avoid large-shouldered jars that taper to a much narrower neck, for the same reason as for bottles. When it comes to defrosting, allow jars to defrost overnight in the fridge, so that their temperature comes up gradually, avoiding any sudden shocks. Following these simple guidelines should ensure that your jars live to see another day and your frozen foods are ready to eat when you retrieve them from the freezer.

Have you used glass jars to freeze food at home? If you have any tips or hints, be sure to share them with us on Facebook, Twitter or Instagram. We’d love to hear your lockdown stories!