Monitoring aldehyde production during frying by reversed-phase liquid chromatography

Acrolein (2-propenal) and other low molecular weight aldehydes (LMWAs) formed by degradation of the frying medium (triglycerides) were monitored by liquid chromatography (LC) during preparation of fried items. LMWA contents of coatings from codfish and of doughnuts and their volatiles that codistill with steam are monitored by trapping the vapors and distillate from the food matrix in a 2,4-dinitrophenylhydrazine solution. The resulting hydrazones are partitioned from the aqueous phase, first into isooctane and then into acetonitrile for LC analysis. The hydrazones are separated and quantified on a C18 reversed-phase column with acetonitrile-water as the mobile phase. LMWAs are confirmed by gas chromatography/mass spectrometry. No difference was found in LMWA content in coatings from fish fillets fried at 182 or 204 degrees C. Cake doughnuts were higher in acrolein content than yeast-raised doughnuts prepared under similar conditions. Freshness of the frying medium, frying time, and batch size did not seem to influence LMWA production from doughnuts. Results indicated that most of the LMWAs formed codistilled with steam during frying rather than remaining with the food item.