Callum is going through a spitting phase at the moment too. I have no idea what's causing it - other than a sneaking suspicion he just thinks it's funny
Once he starts spitting I give him a few more chances to eat that food, then I'll try the other stuff I've got out for tea and offer water. If he keeps spitting then meal time is over ... depending on the time of day and what he's already eaten I just try again in half an hour or leave it.
I haven't worked out how to stop the spitting game but I'm just hoping the fun wears off soon I spose.