Reply #7: No, it takes yeast a lot longer than that to multiply and digest

[Warpy]

all the carbohydrate in the flour. Instant yeast isn't a different animal, just a different preparation of the same animal.

My own guess is that the bread wasn't kneaded long enough to develop the gluten fully. The best way to judge a dough's readiness is the windowpane test, pick up the dough and see if you can stretch it into a translucent, thin layer at least a half an inch wide. If you can, then it's been kneaded enough.

Still, if those loaves are too dense to use for sandwiches or toast, consider slicing them thin and putting them into a slow oven to turn into Melba toast.

Very little bread is a true failure, only if it's burnt to a cinder.