Wouldn't each taste combination then break into individual vectors for intensity?
Because sweetness that is setting off every sweet receptor like it's on fire is definitely a different taste than one that is setting off only enough to meet the threshold for your brain to go "oh, i taste sweet".
If combo 2 is, say, "sour + salt" -- the actual taste range for Combo 2 would be the whole range from "barely enough sour to taste" to "your mouth cannot process any more sour than this" coupled with the same for salty.
So really, what you need is a simple data structure with a vector for each of the 5 tastes, ranging from (undetectable) to "every receptor that can recognize this taste is currently screaming at your brain at maximum volume". Like a 0 to 100 scale would work.
So you'd have 31 possible combinations of flavors, but each combination would have a *very* wide range of expression based on the relative intensities.
And you'd have one (void) which wouldn't need intensity, as everything would have to be at zero.