As a species, humans have really come a long way from the era of hunting and gathering. Far gone are the days of preserving everything through drying processes, salting, fermentation, or whatever other methods could be done quickly and safely. Now, we freeze.
Dropping the temperatures of foods drastically slows processes of spoilage down significantly and kills the many microbes that would catalyze spoilage. Not only is freezing food effective, it's also super easy for anyone with a fridge or freezer. According to the USDA, you can store most soups in the fridge for about three days. But when freezing your soups and thawing them out, you need to be a bit more discerning about what your soup is made of.
Typically a soup will last up to three months in the freezer. But the variability is high, depending on the ingredients present in the soup and whether the freezing process was done correctly. As with any other food that seems to have been left alone for an uncomfortably dubious amount of time (say 2 years, for instance), it's best to trust your gut when inspecting old soup. If you feel uneasy, it's usually best to just throw it out.
According to Martha Stewart, the most important factor to think about when freezing your soup is speed. The speed at which your soup goes from hot to cold to frozen will determine whether or not your soup goes bad in the freezer. Faster is better, so you want to try and get your soup down to smaller amounts and containers. Smaller units will cool faster and more uniformly than a large amount will. To actually cool the soup down, the best (and fastest) way is to place the container of soup in a larger vessel filled with ice water. Be sure to stir it once in a while to make sure it cools uniformly. Then it just comes down to keeping the soup airtight and, of course, not forgetting about it once it's in the freezer.
Thawing the soup is a bit more straightforward. The USDA recommends the cold water method, refrigerator, and proper appliance methods when thawing frozen foods. The cold water method is just running the frozen food under cold water to thaw the food gradually. Although it is faster than the fridge method of leaving frozen food in the fridge overnight, the cold water method requires a bit more attention. So, we typically turn once again to the wonderful technology of the microwave, which can defrost frozen food rapidly.
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