How does the carrot in deep fryer trick work?
As to the science behind why this works, I can only guess.

However, as to other things you can try for this trick, I managed to find some references from old cookbooks about using slices of potato for clarifying their deep-fryer oil. Other suggestions were a slice of bread or lemon peel. Weird — but interesting.

The Young Woman's Journal, Volume 12 (1901)



Mrs. De Graf's Cook Book (1922)



Olive Oil: From Tree to Table (2007)


  When you have finished frying, clarify the oil by frying a piece of bread, a strip of lemon peel, or a slice of potato in it.