There are two main ways to think about the differences between stock and broth: how they're used and how they're made.
Let's take a look at both and then talk about what this means for our cooking!
How Stocks and Broths Are Used
In classic French cuisine, stocks are considered to be an ingredient that's used to make other things. They're typically left unseasoned or only minimally seasoned (i.e. little or no salt or other seasonings) so that they can be used in as wide a variety of ways as possible.
Stocks can be used to make soup, reduced into a sauce or a glaze, or used to make a risotto—all these things can be made from the same batch of stock.
Broths, on the other hand, are less of an ingredient and more of a food that can be consumed on its own. They are usually salted and seasoned, and can be sipped just like that or used to make a simple soup.
You could argue that just by adding salt to stock, you have turned it into a broth. In fact, this is how the difference was explained to me when I was in culinary school!
Because broths have been salted, this restricts the ways they can be used. You can use it to make soup, but you can't reduce it down to a sauce or use it in a risotto without risking an overly salty dish. A broth might also have been spiced or seasoned in such a way that its flavorings aren't appropriate for all dishes.
This definition of stocks as an ingredient and broths as a food product is the way classically trained chefs tend to think about such things in their restaurant kitchens. You can read more about this in Larousse Gastronomique or in The Professional Chef from the Culinary Institute of America.
How Stocks and Broths Are Made
Another way to think about stocks and broths is in terms of how they're made.
Stocks are typically made from meaty raw bones, leftover carcasses (like a chicken carcass), and meat and vegetable scraps. In the case of vegetable stock, only vegetables are used.
These stocks are usually simmered for several hours to extract as much of the flavor and nutritional value from the ingredients as possible. If you're making a chicken or beef stock, you also extract collagen from the bones and cartilage, which adds body and silkiness to the finished stock.
Broths are usually much lighter and have less body than stocks. They're most often made from poaching meat, vegetables, and seasonings in water for a relatively short length of time--often the length of time it takes for the meat to cook or the broth to pick up some flavor! For instance, the liquid left behind after poaching chicken is a broth.
This is how many modern chefs and food professionals think about stocks and broths. You can read more about this perspective in The Food Lab by Kenji López-Alt.
Stock vs. Broth: Which Should You Use?
Think of this like a spectrum with homemade stocks at one end and broths at the other, and within this spectrum, there is a range. You can have stocks that have been seasoned with salt and are ready for drinking (this is what's marketed as “bone broth”). You can also have light broths that have little or no salt, and can therefore be used in similar ways to unseasoned stock.
So which should you use? By and large, you can honestly use either stock or broth in almost any preparation in your kitchen. We're home cooks who are using what we have, not restaurant chefs trying to get a 5-star review.
Just know that a rich stock will result in a richly flavored dish while a light broth will result in a lightly flavored dish. Neither is necessarily better or worse; they're just different.
The big caveat is the salt. If your stock or broth has been salted, be very careful of how you use it. If it reduces down at all, this will likely result in an overly salty dish. If you've made homemade stock, it's best to wait to salt it until you're actually using it in your recipe.
What About Store-Bought Stocks and Broths?
In my experience, commercial brands tend to use the terms “stock” and “broth” pretty much interchangeably. The products have seemed virtually identical to me when I've tried them.
These store-bought stocks and broths are also usually closer to the “broth” end of the spectrum. They tend to be lightly flavored and lack the silky body of a long-simmered homemade stock. As such, they'll result in a more lightly flavored dish than if you used homemade stock, but still something that's plenty worthy of serving for dinner.
So, yes, you can buy either stock or broth for your recipe. But having said this, I highly recommend buying sodium-free or low-sodium versions. This will give you the most flexibility and allow you to salt your dish to your personal taste.
Want to Make Some Stock?!
Here are a few great recipes!