Cholesteryl Fatty Acid Esters and Free Cholesterol in Food of Animal Origin

ABSTRACT Cholesterol is the main sterol in animals and has an essential function as a cell stabilizer. Besides the free form, cholesterol can also be bound to fatty acids (cholesteryl esters, CEs), which are a storage form. Although much is known about the occurrence of cholesterol, there is little data on its esters since cholesterol is usually determined after saponification. In this study, gas chromatography with mass spectrometry (GC/MS) was used to analyze 23 samples of animal origin on free cholesterol, minor sterols, and intact CE (omitting a saponification step). The highest amount of CE‐cholesterol was found in lamb meat and lamb kidney fat (25 mg/100 g fat), and the lowest in Grana Padano with 1.5 mg/100 g fat. The proportion of CE‐cholesterol to the total cholesterol content ranged from quite low 0.5% to a considerable 36% contribution. A higher fat content was correlated with lower total cholesterol, as well as both free and esterified cholesterol. Esterified to cholesterol, mainly saturated fatty acids could be identified, but also high shares of 18:1 n ‐9 and 18:2 n‐ 6. Within the minor sterols, the pattern differed between free and steryl ester (SE) fractions. Free campesterol levels were 20%–48% higher than in the SE fraction, whereas β‐sitosterol levels were 5%–43% lower. The high level of 18:2 n‐ 6 in the CE fraction and the more prominent role of β‐sitosterol in the SE fraction indicated that these are stable compounds that may be formed from fresh items in the feed. Practical Applications : This study should add to the data on cholesteryl ester (CE) quantities in food of animal origin. Since the available data on the bioavailability of CEs is scarce, a separate study of free and esterified cholesterol would be necessary. The amount of cholesterol obtained by saponification might be different from the actual uptake. With the present method for analyzing intact CEs, the difficulties arising from their small quantities and chemical properties (degradation during analysis) could also be overcome. In matrices that have more than one main sterol, the information about the fatty acid moiety gets lost after saponification. Here, the analysis of intact steryl esters (SEs) is important to gain structural information. Additionally, the results help to understand which substrates (fatty acid or sterol) are preferentially incorporated into the SEs. This can be used in other studies that focus on biological synthesis or the identification of unknown SEs.