Recipes say stock. The carton in the store says broth. People use the words as if they are the same thing, and then a recipe comes out thin and nobody knows why.
There is a real difference and it comes down to one thing: bones.
The Actual Difference
Stock is made from bones. Simmered long — four to eight hours — so the collagen in the joints and connective tissue breaks down into gelatin. Stock is traditionally unseasoned.
Broth is made from meat. Simmered shorter — one to two hours — and seasoned, because it was originally meant to be drunk on its own.
So stock has body and broth has flavor. That is the whole thing.
The Test That Tells You Which You Have
Chill it.
Real stock sets to a wobble, like a soft jelly, because of the gelatin. Broth stays liquid.
This is also how you find out whether the carton you bought is actually stock. Much of what is sold as “stock” in stores stays completely liquid in the fridge, which means it has no meaningful gelatin in it and is really broth with a different label.
Why It Matters in Cooking
Gelatin gives sauces body. A pan sauce or a gravy made with real stock coats the back of a spoon. Made with broth it stays watery however long you reduce it, and people add flour or cornstarch to fix a problem that was never a thickening problem.
Gelatin gives mouthfeel to soup. That rich, slightly sticky quality of a good chicken soup is gelatin, not fat and not salt.
Broth is better when you are drinking it or when the liquid is the final thing rather than an ingredient — a simple noodle soup, a light vegetable soup.
For risotto, braises, gravies and reductions, you want stock.
What About Bone Broth?
Bone broth is stock. It is stock simmered even longer, often with a splash of vinegar to pull more out of the bones, and then seasoned and sold to be drunk.
The name is a marketing word, not a technical one. If you make it at home you are making stock.
Which to Buy
Read the label and look at two things.
Sodium. Buy low sodium or unsalted whatever the name says, because you will reduce it and concentrate the salt.
Whether it gels. The only reliable test. Put the carton in the fridge overnight and look.
Better than either: a carton of broth plus a packet of plain gelatin. A tablespoon of gelatin stirred into a quart of broth gives you most of what stock does, for almost nothing.
Make Stock Instead
Keep a bag in the freezer. Chicken carcasses, onion skins, carrot ends, celery tops, parsley stems.
When it is full, cover with cold water, bring it barely to a simmer, and leave it four hours. Do not boil it or it goes cloudy.
It costs nothing, because all of it was going in the trash.
