F. LIN, Department of Nutrition and Food Science, University of Maryland, Skinner Bldg Room 0112, College Park, MD 20742 and M. M. Giusti, Department of Food Science and Technology, Ohio State University, Ohio State Food Science and Technology, 2015 Fyffe Road, Columbus, OH 43210.
Isoflavones found in high concentrations in soybeans have received great attention due to their potential beneficial effects in human health. Our previous research found that dietary genistein was transferred and accumulated into the egg yolks of Japanese quail. Since soybean meals accounts for approximately 25% of the poultry feed ingredients, commercial eggs may also contain soy isoflavones. Our objective was to determine whether isoflavones are present in commercial eggs; and if so, the chemical forms and concentrations of those isoflavones. Commercial eggs of 12 different brands, including regular and specialty eggs with natural, organic, or vitamin E enriched claims, and a typical poultry diet were analyzed. Egg yolks, and pulverized diet were extracted in 80% methanol and analyzed by HPLC. Some egg yolk extracts were also incubated with b-glucuronidase before HPLC analyses for quantitation of total isoflavones. About 5.5 mg/g total isoflavones (normalized to aglycone form) were found in the diet, among which 53% was genistein derivatives, 40% daidzein derivatives, 7% glycitein derivatives. Daidzein and genistein were found in all eggs evaluated, and the amounts of daidzein and genistein were highly correlated (r=0.866). However, the ratio of daidzein to genistein in the egg averaged 3.5:1, which was much higher than that in the diet (0.7:1). It is possible that more daidzein than genistein were transferred to the egg, or that genistein is easier to metabolize and their metabolites are present rather than the aglycone. No significant difference was found between isoflavone contents of regular and specialty eggs. The results showed that a mixture of isoflavones in the diet could be transferred into the egg yolks, and that commercially available isoflavone-enriched eggs could be developed by manipulating the diet of hens. The cholesterol-reducing property of isoflavones could make eggs more appealing to consumers.
Session 33F, Nutraceuticals & Functional Foods: Antioxidants and phytochemical analysis