In "Some Like It Hoth", Hurley comments on some sandwiches, "Ham and cheese. With my secret garlic mayo!". Since all ranch dressing is is basically flavored mayonnaise (usually with a garlic element), this suggests that it was Hurley who actually invented the ranch dressing in the first place.
This seems unlikely since the food is dropped onto the Island by a third party, which means it is manufactured elsewhere and subsequently slapped with a DHARMA logo. The only way this would be possible is if Hurley made it off the Island and back to this third party or, in an even more unlikely event, communicated from the island his recipe to this party.