It's not really about a minimum number, it's more about thinking what's going to run at the same time, because some appliances eat up a ton of power simultaneously.
Ideally you'd have at least 6-8 outlets spread around the kitchen, but the key thing is not to plug the microwave, toaster, and air conditioner into the same circuit because your breaker will trip; it really happens a lot.
If you're doing a renovation, consider dedicated outlets for the heavy-duty appliances (fridge, air conditioner) and leave several multiplex outlets for everything else, so you don't end up with cables tangled everywhere or constantly having things shut off on you.