Formation of Cholesterol Oxidation Products in Marinated Foods during Heating

Abstract

The objectives of this study were to develop a gas chromatography-mass spectrometry (GC-MS) method to analyze the contents of cholesterol oxidation products (COPs) in marinated eggs, pork, and juice and to compare the effect of heating time and soy sauce or sugar on the formation of COPs. By using a silica cartridge for purification and GC-MS with selected ion monitoring for detection, seven COPs, including 7alpha-hydroxycholesterol, 7beta-hydroxycholesterol, 5,6alpha-epoxycholesterol, 5,6beta-epoxycholesterol, 5alpha-cholestane-3beta, 5,6beta-triol, 5-cholesten-3beta-25-diol, and 7-ketocholesterol, as well as internal standard 5alpha-cholestane, were resolved within 16 min by using a HP-5MS capillary column. During marinating, the levels of most COPs followed an increasing trend with increasing heating time. However, a higher amount of COPs was generated for ground pork as compared to eggs. The incorporation of soy sauce or sugar (1 and 10%) was effective in inhibiting COPs formation, with the latter being more pronounced than the former in both marinated eggs and pork.

Thermo-oxidation of cholesterol: Effect of the unsaturation degree of the lipid matrix

“…Dominancy of β-epimer in both 7-hydroxy and epoxy derivatives was observed, which may be due to steric hindrance of the hydroxyl group at position 3 (Lee et al, 2006); other authors have also observed this trend (Lampi, Juntunen, Toivo, & Piironen, 2002;Yen et al, 2010). Both epoxy compounds can give CT under acidic conditions (Lee et al, 2006).…”

“…This might be attributed to the conversion from 7-hydroxy derivatives into such COP (Lee, Chien, & Chen, 2006;Chen, Chien, Inbaraj, & Chen, 2012).…”

“…Both epoxy compounds can give CT under acidic conditions (Lee et al, 2006). CT was formed at advanced stages of oxidation, when the epoxy compounds (and other compounds) had already started their decline.…”

Cholesterol oxides content in selected animal products determined by GC‐MS

“…The SIM mode was used to detect COP. The elution order of COP was as follows: 26.5-26.9 min m/z 353, 366 for 19-OH, 27.2-27.6 min m/z 456 7b-OH, 27.8-28.1 min m/z 474 for 5a,6a-EP, and 5b,6b-EP, 29.0-29.3 min m/z 403 for triol, 30.0-30.5 min m/z 131 for 25-OH and 472 for 7-ketocholesterol [13]. Other molecular ions used to determinate particular COP are presented in Table 1.…”

Sample preparation: A critical step in the analysis of cholesterol oxidation products

“…These proportions should be constant; otherwise, selective losses of these lipids, into upper phase, may occur (Christie, 1993;Guardiola et al 2002). Nevertheless, it seems that this critical aspect is often overlooked in some studies (Chen, Lu, Chien, & Chen, 2010;Lee, Chien, & Chen 2006;Lee, Chien, & Chen 2008).…”