Mason jars offer a convenient way to freeze soup without the hassle of saggy plastic bags or cumbersome storage containers. The rigidity of the glass makes filling the jars a breeze, and when it comes time to thaw, removing the soup is just as simple. A strong, wide-mouthed mason jar offers plenty of room for liquid expansion as the soup freezes, resists breaking and keeps the soup safe to eat for months in your home freezer.
The Right Jars
Only use jars made for the purposes of freezing and canning, which are made of tempered glass that withstands drastic changes in temperature. Ordinary glass jars are made of thinner glass than mason jars and cannot withstand the expansion that comes with freezing liquids. Jars with thinner necks often snap at the neck during freezing, which is why the wide mouth of the mason jar is preferred. The wider neck also makes it easier to remove the thawed soup from the jar, especially for thicker and heartier soups such as split pea soup or those containing large pieces of meat or vegetables.
Fill It Up
Cook and cool the soup completely before filling the mason jars for freezing. Freezing soups that contain potatoes may take some experimentation. Potatoes do not always freeze well, so you might want to remove the potatoes prior to freezing. Pour the soup into the mason jars, leaving about an inch of headspace between the soup and top of the jar. That provides room for the soup to expand as it freezes, without subjecting the glass jar to a potentially dangerous degree of pressure. Close the lids tightly and pop the filled mason jars in the freezer, where they keep for up to six months.
When you are ready to eat the frozen soup, thaw it in the refrigerator. Once thawed, heat cream-style soups in a double-boiler over boiling water, stirring constantly to re-blend the contents and smooth the consistency. Reheat all soups to a temperature of 165 degrees Fahrenheit, which ensures thorough cooking.
One Word of Caution
It's important to note that, while tempered Mason jars are relatively resistant to temperature-related breakage, they're still made of glass and are correspondingly fragile. It's best to position them along a wall of the freezer, or in the door, or - in a chest freezer - in a basket, so they have some support and aren't likely to fall as foods are moved around and removed.