Yolk of the Century Egg (Pidan) Contains a Readily Digestible Form of Free Vitamin B₁₂

Abstract

In this study, we determined the vitamin B₁₂ content of commercially available century eggs (pidan) and characterized their vitamin B₁₂ compositions in detail. The egg yolk and white of century eggs (each 100 g wet weight) contained 1.9±0.6 and 0.8±0.3 μg of vitamin B₁₂, respectively. The vitamin B₁₂ compounds purified from the egg yolk and white were identified as vitamin B₁₂ using liquid chromatography-electrospray ionization/tandem mass spectrometry. The vitamin B₁₂ present in the yolk or white of century eggs was recovered completely in macromolecular fractions, but not in free vitamin B₁₂ fractions by Sephadex G-50 gel filtration. However, with respect to the vitamin B₁₂ bound to protein in the century egg yolk, approximately 52% of the free vitamin B₁₂ was formed during in vitro gastric digestion and no free vitamin B₁₂ was detected in the egg white.