This is the bill text: "SECTION 1. It is the intent of the Legislature to enact future legislation limiting the sale of ultraprocessed foods in California schools."
That's it.
It's fairly well understood what makes junk foods tasty without much nutritional value. Salt and sugar play a big role. Those aren't "ultraprocessed".
Bread is "ultraprocessed". The number of steps from wheat to bread is large, and the output looks nothing like the input. Here's how "artisanal bread" is really made.[1]
It's the ingredients, not the processing.