On the matter of Citric Acid...

[ThePieMan]

"9.10 CONTROLLING FLAVOR DEVELOPMENT IN FRYING OILS
The general factors that help inhibit frying oil deterioration include choosing fresh oil with good initial quality that has no prior oxidation and low amounts of catalyz- ing metals. The extent of the degradation reactions of hydrolysis, polymerization and oxidation can be controlled by carefully managing frying conditions, such as temperature and time, exposure of oil to oxygen, continuous frying, oil filtration, turnover of oil, and addition of citric acid, antioxidants and/or anti-foam agents."(source:https://www.perlego.com/book/1696374/advances-in-deepfat-frying-of-foods-pdf p.210) 

There has been some discussion and speculation on a) whether citric acid was being added to the frying oil, and b) as to whether it contributed a lemon-ish flavour to the oil. Well according to the above source, if citric acid is being added to the oil, it does contribute to the flavour of the oil, in-so-far-as it aids to control the degradation reactions of various fatty acids under exposure to oxygen and high heat in the frying oil. These reactions apparently contribute to the tasting quality of, "deep fried flavour" of a cooking oil.