On the principle of a forbidden item convey taste, and with it "forbiddenness," as manifest in hot split beans and vinegar vs. cold split beans and vinegar. Also, on adding a flavor that is to the detriment of the food - and whether that is then prohibited is a machloket. Plus, the biblical source, going back to Midian. Plus, the time-frame for food to go bad... or for a change in taste to automatically be enhanced.