Frying polar compounds formation

Razali, I. and Badri, M. (1993) Oil absorption, polymer, and polar compounds formation during deep fat frying of french fries in vegetable oils, in Proceedings of the 1993 PORIM International Congress, Update and Vision (ed Y. Basiron), Kuala Lumpur, pp. 80-89. 

During frying, hydrolytic, oxidative and pyrolytic (Pokomy, 1989) reactions occur and these lead to the formation of volatiles, nonpolymeric polar compounds of moderate volatility, dimeric and polymeric acids and partial acylglycerols as well as free fatty acids (Chang et aL, 1978). These reactions are responsible for a variety of physical and chemical changes that may be observed in the oil during frying. These physical and chemical... 

FIGURE 1.6 Total polar compounds (TPC) over frying time for canola oils. Oils with the same letter as subscript displayed no significant differences in rates of TPC formation at p < 0.05. (From Normand, L., Eskin, N.A.M. and Przybylski, R. 2001. J. Amer. Oil Ghent. Soc. 78 369-373. With permission.)... 

FIGURE 5.4 Formation of polar compounds in oils during rotational frying. 

Nitrobenzene was used as solvent in an investigation as it is frequently used in Friedel-Crafts reactions and facilitates the solubility of aluminum chloride. However, nitrobenzene may inhibit the formylation reaction as the polar NO2 group competes with CO in the protonation reaction (CHO ), resulting in low or no reactivity. Another possible reason for the apparent unreactivity of phenol under these conditions was proposed by Olah ° and involves the formation of phenyl formate (0-formylation of phenol). These compounds decarbonylate easily, instead of undergoing acid catalysed Fries rearrangement to the aldehyde [Eq (2.13)]. 

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