Frying influence on virgin olive oils by monitoring change of aliphatic monoaldehydes
When virgin olive oil (VOO) have been fried long time at high temperature, some aliphatic monoaldehydes including hexanal, heptanal, octaldehyde, nonanal and decanal were found in fried VOO and food samples. The HPLC method has been developed for determination of aliphatic monoaldehydes in VOO and food samples after different fried conditions. These five aliphatic monoaldehydes could be separated and analyzed in 60 min on reversed phase ODS column with methanol/0.1% acetic acid water solution mobile phase at 1.0 mL min-1 flow rate, after being derivatized with 2,4-dinitrophenylhydrazine (DNPH). The method was validated with recovery results ranging from 86% to 114%. Calibration plots of aliphatic aldehydes were linear (r≥0.9991) in the concentration range from 1.0×10-6 to 1.5×10-4 mol L-1. The LODs were between 6.5×10-8 and 3.98×10-7 mol L-1. The proposed method provides a reliable and sensitive quantitative evaluation for aliphatic monoaldehydes in fried oils and fried potatoes samples. The experiments results verify that the VOOs are not suitable to be fried long time at high temperature. The frying time should be less than 3.0 min, and the frying temperature should be below 150 °C for the healthy diet.