In order not to offend the owners who have spent time and energy on cooking, it is worth to act more delicately.
Make out
Here are some phrases by which you can distract yourself from attention and not cause the wrath of the hosts:
No, thanks, I'm saving the place for another dish.
I can not wait to try another dish!
From such an ingredient I have a bad stomach, so I better refrain.
It looks very appetizing, but I still want to eat what's on my plate.
I'm so full that I will not get into a piece! Thank you for a great dinner!
I'll leave it for the second call! (And then "forget" to put yourself this dish or say that you are full.)
Speak cheerfully cheerful, smile. And try to quickly transfer a plate with a dish that is unpleasant to you neighbor.
Try quite a bit
If the owners do not surrender or you feel obligated, try to take a small portion of an unpleasant dish. Instead of saying "no", put yourself on a plate quite a bit. So you show respect for whoever prepared it. Of course, to take one slice of potatoes or one drop of sauce would be strange, but you can take one or two spoons.
If the dish you do not like, but you still want to finish eating a portion, try to "seize" it with something tasty. Or richly season with its sauce.