Stability of Plant Sterols in Ingredients Used in Functional Foods

Abstract

The content of plant sterol (PS) and their oxidation products (POPs) in eight ingredients used to enrich functional foods was studied. A gas chromatographic (GC) technique with mass-spectrometric detection was used for identification, while GC with a flame ionization detector (GC-FID) was used for quantification. β-Sitosterol was the most abundant phytosterol, and the main POPs found were derived from this compound (7α/β-hydroxysitosterol, 7-ketositosterol, and sitostanetriol). The total amount of POPs found in the ingredients ranged from 29.03 to 110.02 μg/100 g PS. The β-sitosterol oxidation rates ranged from 10 to 50 μg β-sitosterol oxides/100 g of β-sitosterol. In view of this low rate of oxidation in the ingredients tested, it can be concluded that the PS remain stable in these ingredients. Significant correlations (p < 0.01) were found between total oxysitosterols versus β-sitosterol contents (R(2) = 86.5%) and between total POPs and total PS (R(2) = 81.6%).

Sterol stability in functional fruit beverages enriched with different plant sterol sources

“…The differences found in the sterol profile in PS-enriched foodstuffs in the literature in comparison with our own samples could be attributed to the origin of the sterols used in enrichment, as recently confirmed by González-Larena et al (2011) in several PS ingredients. In two studies with orange juices, samples enriched with esterified PS (Mezine et al, 2003) (PS origin not specified) and PS from vegetable oils (Devaraj, Jialal, & Vega-López, 2004), a PS profile in which the predominant representative was β-sitosterol (40-50%) in a proportion lower than that found in our study (see Table 2) was reported.…”

“…Then, after phase separation, the chloroform phase was concentrated in a rotary evaporator and dried with nitrogen. The lipid fraction obtained (75 mg approximately) was processed by the method described by González-Larena et al (2011). Briefly, IS (2 mg of epicoprostanol) was added to the lipid fraction and hot saponification (3 mL of 1 N KOH in methanol at 65°C during 1 h) was performed.…”

“…Therefore, for the identification of POPs in beverages, mixtures of β-sitosterol, campesterol and stigmasterol oxides were thermo-oxidized and identified by gas chromatography-tandem mass spectrometry (GC-MS/MS) (González-Larena et al, 2011). Their collision energies were optimized and the identifying parameters for each phytosterol oxide were obtained as reported elsewhere.…”

“…With the lipid fraction obtained, we applied the method of González-Larena et al (2011). Briefly, IS (9.82 μg of 19-hydroxycholesterol) was added to the extracted lipids.…”

“…While the negative biological effects of COPs have been extensively studied, and these compounds are now known to be implicated in the initiation and progression of major chronic diseases (atherosclerosis, neurodegenerative processes, diabetes, among others), the biological effects of POPs are still unclear and contradictory (García-Llatas & Rodríguez-Estrada, 2011;Hovenkamp et al, 2008;Otaegui-Arrazola, Menéndez-Carreño, Ansorena, & Astiasarán, 2010;Ryan, McCarthy, Maguire, & O'Brien, 2009). As has been recently reported, the presence of POPs in enriched foods may come from the PS source used for enrichment (González-Larena et al, 2011). Accordingly, several factors may contribute to their formation: the high temperatures involved in obtaining PS (Moreau, 2004), the different food characteristics (Ryan et al, 2009), and the processing conditions employed after the addition of these functional ingredients to different food matrices (Menéndez-Carreño, Ansorena, & Astiasarán, 2008;Soupas, Huikko, & Lampi, 2006).…”