Topical Area: Dietary Bioactive Components
Objectives : Soybean meal serves as the major protein source and base ingredient for nearly all poultry diets. Previous studies have detected isoflavones in chicken eggs, with a large amount of variability. However, the data on isoflavones in processed eggs and egg products on the U.S. market are still limited. The objective of this study was to analyze isoflavones and their metabolites in selected processed egg samples.
Eleven samples of fresh or dried whole eggs, egg yolk, and egg white from various processors were provided by American Egg Board. The analyses of isoflavone were performed in a HPLC-MS system after extraction and deconjugation. The data were expressed based on the fresh weight.
Results : In all 11 samples, two isoflavone glucosides, three isoflavone aglycones and equol were detected and quantified. Daidzin, glycitin, daidzein and equol were found to be the major isoflavones. Surprisingly, genistin, one of the major isoflavone glucosides in soybean, was not found in any samples. The aglycone genistein, however, was found to be in much lower concentrations compared to other aglycones. The concentrations of individual isoflavones varied significantly among different samples. Total isoflavones in whole eggs, egg yolk and egg white were calculated as 2.4 ± 1.0 (mean ± SD, n = 5), 2.9 ± 1.7 (mean ± SD, n = 4) and 1.2 (mean, n = 2) mg/100 g, respectively. As a metabolite from daidzein by bacterial flora in the intestines, equol was found to be a dominant isoflavone, counting 23.9%, 33.0% and 21.9% of the total isoflavones in whole eggs, egg yolk and egg white.
Isoflavones and their metabolites existed at significant concentrations in processed eggs available in the U.S. Considering the estimated consumption at 274.2 eggs per person (2017) in the U.S., eggs and egg products could be an important source of isoflavone intake for American people. Even though only 23% to 30% of Western adults are estimated to be equol-producers, consuming eggs allows everybody to ingest equol, which could impact the evaluation of the health effects of isoflavone intake in the U.S.
Funding Sources : American Egg Board; USDA-ARS