The Storage Mistake That Could Lead To Fizzy, Fermented Soup

Who wants to eat fizzy soup? It's not exactly the texture you imagine when digging into a silky cream of celery or roasted tomato soup, but your leftovers could turn out carbonated if they're stored in a particular way. If you keep your soup in a glass container in the fridge, it could become fizzy, even after just a day or two. However, if you keep it in a plastic container like Tupperware, it's unlikely you'll have the same problem.

So why does this happen? Essentially, your dish is fermenting in its glass container. Glass is widely used to ferment foods (on purpose) like kombucha, yogurt, and sourdough starters because it doesn't rust or leach chemicals, which means that chemicals can't penetrate through it and won't react with its walls. So glass is great for fermenting, but not so great if you're trying to keep your soup's texture intact.

Carbon dioxide can leak out of a plastic container, but it gets trapped in your soup in a glass one, producing bubbles. Some canisters meant for fermenting have a vent to release carbon dioxide, but of course, if you're storing your soup in a typical glass container, you probably don't have that option. 

If you catch the fizziness early on (like in the first day or two), you may be in the clear to keep eating your soup. However, proceed with caution if it's showing a lot of bubbles, and remember that soup only lasts up to four days in the fridge. There are also a few different techniques you can try to revive a carbonated dish. As long as the flavors mesh with the rest of your ingredients, you can try heating sliced onions and palm oil inside a pot before throwing in the rest of the soup to reheat. Or, counteract sourness with a little baking soda, sugar, salt, or butter.

But we know that prevention is better than a cure, and the easiest way to avoid a carbonated soup is to simply store it in a plastic container. Try to let it cool completely on the counter first, but if two hours have gone by and your dish is still warm, it's better to get it in the fridge than let it continue to sit out. If you want to speed up the process, you can even plop your soup pot in an ice bath. But either way, keep it in plastic to retain its non-fizzy texture.