Okay, so I’ve heard some people saying some whack things about ketchup. The logic I’ve heard goes like this: “A tomato is a fruit. A jam is a congealed spread created from fruits. A tomato is a fruit. Ketchup is made from tomatoes. Therefore, ketchup is a jam.”
This is wrong for multiple reasons. First and most relevantly to this site, a tomato is not a fruit culinarily. Sure it may be a fruit botanically, but that is irrelevant. Even if you were a botanist or farmer or someone that had a valid reason to refer to a tomato as a fruit, this clearly is not the definition referenced by the definition of jam. Jam is only concerned with the culinary properties of jammable items, not how they are grown. Tomatoes are not eaten as fruits. Therefore, ketchup would not meet this definition of a jam.
There are other reasons that ketchup is not a jam however. To start, jam is usually not constrained to only being made with fruit. For one, rhubarb jam is quite popular and delicious. Also though, some people do make jams from more vegetably vegetables like carrots and yes, tomatoes.
Jams are basically always sweet. Even with already sweet fruits, sugar is normally added. To make normal jam from tomatoes, one would have to add a lot of sugar. Ketchup usually has sugar added, but it never reaches the level of sweetness that a dessert has. Plus, it has vinegar added. That is not a flavor one would ever find in jam. It goes very much against the goals of sweetness and fruitiness.
The other big problem with ketchup being a jam is that jams do have to be semisolid. It has to be heated to get its pectin to congeal. That’s what makes it so jelly-like. Ketchup is a little viscous—more than water at least—but it is no where near thick enough to resemble a jam. It flows quite easily. In fact, the main ketchup-seller, Heinz, will reject and refuse to sell ketchup if it is too viscous.
In conclusion, ketchup is not a jam. It is not made with fruit, it is not sweet enough, and it is not very viscous. It is just a kind-of-sweet, vinegary sauce used as a condiment. This is not a bad thing for ketchup—I quite enjoy it—but it is definitely not a jam.