How to Safely Freeze Foods in Glass Jars: A Step-by-Step Guide

Waste not, want not. It’s the mantra of a bygone era that has become relevant today. Saving leftover food to consume later is the right thing to do for your budget and the planet.

Reducing food waste is essential for the well-being of our planet and learning how to freeze food leftovers in glass is sustainable and economical.

Glass is plastic-free (duh), reusable, sustainable, and helps you towards a zero waste in the kitchen. Use these tips for freezing (organic) food leftovers in glass containers.

Tempered Glass

Tempered glass has been through a controlled thermal treatment that makes it stronger and able to withstand extreme temperatures. Glass baking pans and canning jars are two examples of tempered glass that we are most familiar with.

Glass canning jars are ideal for use to freeze leftover food. The glass has been tempered and can withstand the below-freezing temperature of the freezer. Glass jars that have been purchased with food in them are made from tempered glass as well and are safe to use for freezing leftover food.

The various shapes and sizes of glass containers that range from baby food jars to gallon-sized pickle jars can be used for freezing food leftovers as long as the containers are made from tempered glass.

Only use glass jar with a wide top. This makes putting food in the container easy and your food will expand when it is frozen in the freezer so you need the extra space.

What Food Leftovers Can Be Frozen

Any food can be placed in a glass jar and frozen. Cooked or raw beans, liquids from vegetables, cooked meats, pasta leftovers, bread, soup, lemon zest, celery tops, fresh fruits, fresh or cooked vegetables, food scraps for composting, or meat bones to make stock.

Leftover coffee, tea, fruit or vegetable juices, or anything else that you consume can be frozen. Instead of tossing or pouring out small amounts of a food or beverage, freeze the food leftover in glass for later use.

How To Store

2 Jars ready to go into the freezer.

Foods, especially liquids, will expand as they freeze. This expansion must be allotted for when packing the glass jar. Don’t pack a glass jar to the top when filling it for the freezer. Leave 1-inch of headspace at the top of the jar so the food inside will have plenty of room to expand without breaking the glass.

The pictures show 2 jars ready to go into the freezer. One has leftover risotto, the other has water to show that freezing liquids in the freezer is possible.

2 jars in the freezer without the lid.

Allow the food to cool completely before placing the jar in the freezer. Place a piece of freezer tape on the outside of the glass jar and write the contents on it for easy food identification.

Leave the lid off when placing the jar in the freezer and put the lid on after 24 hours. Food expands while freezing and when the lid is airtight on the jar, the pressure in the jar increasing resulting in breaking of the glass.

Frozen solid food and water in jars

How To Stack

Careful stacking is needed to prevent the glass jars from falling out of the freezer when the door is opened and to prevent them from turning over and banging into each other inside the freezer.

Many methods can be used for safe stacking, like racks or bins, the goal is to keep the glass jars of frozen food stable.

How To Defrost

Pre-planning will be needed when using frozen food from glass jars. The jars can’t be placed in hot water or in the microwave to defrost the contents. Place the glass jar in a bowl of cold water until the contents loosen from the sides, then the leftover food can be scooped out of the jar and placed in a microwave-safe container, and heated.

Using wide-mouthed glass jars makes defrosting and extricating the frozen food much easier. Once the food has defrosted enough to turn loose of the jar sides, a spoon can be inserted around the edges to scoop out the semi-frozen food.

Large glass containers, like a Pyrex casserole dish, can be placed in the bottom of the refrigerator for a couple of days to defrost. Never take a glass container of frozen leftover food from the freezer and place it directly into the microwave or oven, the glass (even tempered glass) will break under such sudden temperature changes.

Wash And Reuse

The glass containers and lids can be washed and reused indefinitely. Reduce your food waste, save money on your grocery bill, have convenient frozen food on hand, and reduce the amount of plastic (one-time use freezer bags) you use by freezing food leftovers in glass.