Evaluation of glycerol core aldehydes formation in edible oils under restaurant deep frying

[Display omitted] •The nature of GCAs in nine actual deep-frying systems was firstly reported.•Core aldehyde methyl esterification product was investigated by GC–MS.•GCAs showed a high correlation with polymerized and oxidized products. Glycerol core aldehydes (GCAs) are potentially toxic lipid oxidation products characterized by aldehydic acids bonded to glycerol via acyl groups. This study investigated the profile and change of GCAs in rapeseed oil (RO), high-oleic sunflower oil (HOSO) and cottonseed oil (CO) after frying chicken nuggets (CNs), fish nuggets (FNs) and French fries (FFs) for 60 h in real restaurant frying systems. Three GCAs (8-oxo, 9-oxo, and 10-oxo-8) were identified, with the GCAs (9-oxo) accounting for the highest value (60%), followed by GCAs (10-oxo-8) and GCAs (8-oxo). The total GCAs increased from 1.12 to 2.02 mg/g with frying time from 0 to 60 h in RO used for frying FNs. The FN frying systems produced the largest amount of GCAs, whereas the FF frying systems produced the least. RO contained more GCAs than CO and HOSO owing to its higher unsaturated fatty acid content (91.81%). Furthermore, the GCAs showed a high correlation with polymerized and oxidized products, indicating that the formation of GCAs were related to the oxidative stability of oils. These results may provide insight into the formation of GCAs and their control during frying.