Soup tastes 'brighter and fresher' when you add 1 unusual ingredient

Even your soups can do with a spot of sunshine this winter. Healthy, hearty, and comforting, soups are that one solid winter staple, yet they can get just a tad boring. The good news is that even the humblest of soups can be transformed with this one surprising (and slightly sour) twist.

You would never think it, but it turns out that lemons are your magic ingredient, and a little bit of food theory explains why these sour bundles of sunshine can totally brighten and freshen up even the simplest of soups.

Food writer Mindy Fox at Epicurious said: "Whichever chicken soup route you go, know this: in the end, every chicken soup needs one thing: a lemon".

Whether you decide to add noodles, beans, rice, dumplings, or matzo balls, she insists "lemons are a chicken soup game changer." Just like a vinaigrette on a salad, the pickle on a burger, and the sour cream in a coffee cake, a squeeze of lemon gives chicken soup a game-changing brightness.

But there's definitely a right way to do it.

Mindy explains that the fresh, fruity acid is even more magical and pronounced because it's added at the end.

You'll want to add the juice ideally just before eating, not a moment sooner. This is because you don't want to cook or reheat citrus in your soup. Even cooking for a minute will cause it to lose its punch, and it may even turn bitter.

Simply squeeze your citrus directly into individual bowls of hot soup just before serving.

The reason why it works so well is down to the acid, which balances out all the other elements in your soup. When it comes to Mexican and Asian soups as opposed to Mediterranean flavoured ones, Mindy adds that although they'll work best with lime, if you simply don't have one "don't shy away from an available lemon; you'll still get the bright flavour you're looking for".

As for cold lemons, so that they can release more of their vibrant juices, it's recommended that they're taken out of the fridge a few hours before serving or simply submerged in a bowl of hot water for a few minutes.

Chowhound adds that when it comes to understanding why lemon is such a great ingredient to add, it helps to think of Samin Nosrat's "Salt, Fat, Acid, Heat" theory. When you're cooking, you want to apply just the right balance of those four "cardinal directions".

And while it's hard to go wrong with lemon juice, even a splash of red wine vinegar or sherry vinegar can add a "whole new dimension" to a tomato soup.