I came across an interesting article by Charles Spence and Alberto Gallace entitled "Tasting Shapes and Words" (Food Quality and Preference 22(3): 290-295).
Synaesthesia. This is what doctors call the condition in which people use more than one sense to perceive a stimulus... just like seeing colours when music is played (they are NOT high on drugs) and also like associating shapes or sounds to tastes and flavours (the topic of the paper... please click on the link).
I always thought that people who describe food this way were doing so metaphorically. Just like when wine connoisseurs describe vintages as either sharp or rounded (wines have edges?), smooth or rough (wines have texture like solids?). Apparently, this notion is wrong. There are people who have this synaesthesia capacity and LITERALLY associate taste with shapes and words.