Original ArticleComparison of the cholesterol content of Brazilian chicken and quail eggs
Introduction
Appreciated for their nutritive value and functional properties, eggs are an important item in the human diet. In developing countries, it is often the only animal protein source that is accessible to the general population. It is a major source of dietary cholesterol and consumer concern about the association of cholesterol with coronary heart disease has lowered consumption.
There are some conflicting views and results in relation to the analytical methods for cholesterol. Colorimetric determination of the cholesterol concentrations of eggs and egg products had been questioned because interfering compounds could lead to significant overestimation (Beyer & Jensen, 1989a). The extent of overestimation, however, would depend on the colorimetric method used (Bragagnolo & Rodriguez-Amaya, 1993) and some results (Rangachar, Setty, & Hedge, 1970; Sainz, Gonzales, Roca, & Alemany, 1983) were comparable to those obtained by gas chromatography (GC) or high-performance liquid chromatography (HPLC) as pointed out by Maurice, Lightsey, Hsen, Gaylord, and Reddy (1994). The chromatographic techniques are favored because of their ability to separate and quantify cholesterol specifically, although Maurice et al. (1994) noted that reported levels obtained by GC were higher than those determined by HPLC. Jiang, Fenton, and Sim (1991) found no significant difference in egg cholesterol values obtained by enzymatic, GC and HPLC methods. Based mainly on data from colorimetric assays, the cholesterol content was estimated in the United States to be 550 mg/100 g of egg (USDA, 1975). Reflecting results of chromatographic methods, the revised value is 425 mg/100 g of egg (USDA, 2000).
The extraction and saponification steps had also been assessed. Van Elswyk, Schake, & Hargis (1991) observed that saponification of the lipid extract resulted in a significantly lower value than direct saponification of the sample. However, Bitman & Wood (1980), Fenton & Sim (1991) and Maurice et al. (1994) did not detect significant difference in egg cholesterol determined by these two procedures.
Natural variation between samples has also been reported, the cholesterol level in eggs varying with species, breed, hen's age, egg and yolk weight, and diet (Riad, Kicka, Osman, & Kamar, 1981; Naber, 1983; Al-Zubaidy & Al-Taha, 1984; Villanúa & Villanúa, 1988; Beyer & Jensen, 1989b (1989b), Beyer & Jensen, 1989b (1983); Pandey, Panda, Maitra, & Mahapatra, 1989; Jiang, Cherian, Robinson, & Sim, 1990; Chung, Ferrier, & Squires, 1991; Jiang & Sim, 1991; Maurice et al., 1994). Hargis (1988), however, concluded that dietary, genetic and pharmacological manipulation to reduce cholesterol in eggs have only been marginally successful. Chung et al. (1991) considered selection of eggs for lower cholesterol content impractical under current commercial operating conditions.
Brazil does not have its own data on the cholesterol levels of chicken and quail eggs. This work was therefore carried out to fill this information gap, while taking advantage of refinements in the analytical method. Quail egg has become a popular item in salad buffet tables of Brazilian restaurants.
Section snippets
Samples
Thirty one-dozen packs, 10 packs for each of large white-shelled, large dark-shelled and small white-shelled chicken eggs, were bought at different times from different grocery stores in Campinas, São Paulo State, Brazil during a period of 8 months. From each pack, three eggs were randomly taken, the yolks were separated from the albumen and mixed.
For the quail eggs, 10 three-dozen packs were also purchased from different grocery stores at different times. From each pack, 10 eggs were taken at
Evaluation of the method
The cholesterol contents of three samples of fresh eggs prepared by direct saponification or saponification of the lipid extract are shown in Table 1. For the three samples analyzed, the cholesterol levels obtained by direct saponification were higher than those obtained by saponification of the lipid extract. This finding is in agreement with Van Elswyk et al. (1991), but contrary to Bitman and Wood (1980), Fenton and Sim (1991) and Maurice et al. (1994), who found the same values for both
Acknowledgments
The authors wish to thank the Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) for the financial support and Mr Mark Prescott (University of Liverpool) for recording the MS spectra.
References (24)
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