They normally just play for meal courses don't they? If they really want to make them eat something nasty, just make them eat more of Mel's cooking, with nobody left to advise her, they'll all end up poisoned.
I think in recent years they switched it to having everybody doing the eating trial, partly because of the disproportionate advantage the contestant doing the bug eating trial had on the others in winning over the public, but I don't think it's happened with a three personal finale as of yet.
