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

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.