One possible solution to the transfer problem might be admix the bittering agent with starch, or to find a way of binding it to starch. The intention would be to produce a substance which sticks tenaciously to one’s fingers but is degraded by the amylase that is present in human saliva. If one put one’s fingers in one’s mouth, the bittering agent would be released, but in the absence of amylase, the stuff would stick to one’s fingers and not to a sandwich.
The method would not be perfect because amylases are present in some foods as well as in saliva. There are some fruits, for instance, which produce amylase during their ripening; but it might even be possible to find a polysaccharide that is degraded by salivary amylase and not by other amylases.
Contributors: Mark R. Diamond