>>>so I will yield to John Ryan's ...
>
>Where is the fun in that? ;-)
>
>Here, allow me: sweet is not the opposite of sour. ;-)

yupp, that is the one that was nagging me mostly: if asked to pick the axis/dimension least correlated with sweet, my pick would have been bitter.
And you are probably thinking directly about the PH scale, where alkaloids are not at the sour end ;-))