Revulsion at the prospect of (oral) incorporation of an offensive object. The offensive objects are contaminants; that is, if they even briefly contact an acceptable food, they tend to render that food unacceptable.
Rozin, P. & Fallon, A. E. (1987). A perspective on disgust. Psychological Review, 94(1), 23-41. doi: 10.1037/0033-295X.94.1.23.