Two part question:
(1) How does oil inhibit formation of head in beer? Homebrewers take as gospel that oil-containing ingredients such as nuts will negatively impact head. But I can't find any articles or other materials explaining how and why this is true. I am trying to understand the chemistry of how this works.
(2) Do citrus oils (from citrus zest or orange peel) inhibit head formation? Randy Mosher says that in his experience citrus oils do not affect head.