A sensitive UHPLC-electrospray tandem mass spectrometry method for the simultaneous quantification of 8 oxysterols and cholesterol in oysters (Crassostrea gigas) with different thermal cooking procedures

Oxysterols are oxidation products derived from the oxidation of cholesterol, a process that occurs during seafood processing. These oxysterols not only impact the quality of food, but also are significantly associated with human health and disease. In this work, a UHPLC-MS/MS analytical method was developed and validated for simultaneous quantification of 8 oxysterols and cholesterol. The R-squared (R²) for all oxysterols and cholesterol exceeded 0.9992 within a concentration range of 1.0–5000 ng/mL. The recoveries ranged from 86.66 % to 104.10 % with RSD < 6 %. The present study conducted an analysis of oysters to assess the impact of different thermal cooking methods (boiling, frying, roasting and air frying) procedures on the formation of oxysterols. This study showed that air frying resulted in significantly elevated levels of oxysterols in oyster lipids (P<0.05), mainly 7β-hydroxycholesterol at 6.87±1.23 μg/g, 7-ketocholesterol at 2.87±0.26 μg/g, and 5α,6α-epoxycholesterol at 2.53±0.29 μg/g. Additionally, the production of free fatty acids (FFAs) through oxidation exhibited a similar trend to that observed in the formation of oxysterols. In addition, statistical analysis indicated that the degree of lipid oxidation was positively correlated with the formation of multiple oxysterols.