Forget Flour, Thicken Soups With Dissolving Sweet Potato
Many types of soup like chicken noodle and miso have thin broths, but there are plenty of other varieties where you want a much thicker consistency. Take broccoli cheddar or cream of mushroom, for example. Despite not being particularly hearty, they're still considered heavy soups because of how thick the liquid is, and if they're too thin, they start to taste almost watery. So what gives these types of soups their signature viscous consistency?
Well, if you look up a recipe for a chowder or cream-of-anything soup, you'll find that there are almost always the two same thickening agents present: cream and flour. If you skip the cream and flour altogether, you'll likely end up with a considerably thinner soup, however, if you replace the flour with a different form of starch, you might actually have better results. You might be tempted to reach for cornstarch, beans, lentils, and rice are all viable alternatives too, but by far the most effective option is potatoes, ideally sweet potatoes.
What happens when you thicken soup with sweet potato?
If you've ever made potato soup before, you probably already know that you don't have to add cream or flour to it even though most recipes call for the two ingredients. The soup will be more translucent than opaque, but it will still be thick, thanks to the natural starchiness of the potatoes. It also won't have the same chalkiness that flour or cornstarch leaves behind. The same principle can be applied to any other soup.
Potato is an effective soup thickener because of its high starch content, but too much starch isn't necessarily a good thing because it will make your soup gluey instead of thick. That's why sweet potatoes are a better option. Not only do they contribute more flavor by way of their sweetness, but sweet potatoes also contain half as much starch as a regular potato, which happens to be the perfect amount for thickening soup without turning it gummy.
How to use sweet potato as a soup thickener
To use sweet potato as a soup thickener, don't try to add it into the broth raw, because by the time it dissolves in the soup, the rest of the ingredients will be overcooked. Instead, boil the sweet potato until it's fully cooked, then chop it up before adding it in, professional chef Lisa Marley explains to The Guardian. This allows the sweet potato to almost melt into the soup so it can be evenly thickened throughout without any big chunks remaining.
You may be tempted to use an immersion blender to better incorporate the sweet potatoes into the soup, but this isn't the best idea because it releases gelatinized starch into the soup. When starch is gelatinized it adheres to the broth, creating that gluey consistency you want to avoid. This is less likely to occur with sweet potatoes since they're lower in starch, but it could still happen if you're not careful.