Providing what it calls simplicity at its best, Japanese researchers have created an egg that only contains egg white - no golden yolk.
Now, despite what you might think, I'm not a health nut (I couldn't keep a straight face as I wrote that), and DO prefer my eggs to have a yolk - and not even a double yolk, which is why I reveal this phenomenon with much trepidation.
But, as it turns out, the yolk is still there, only it's not yellow, but is white…
Produced in Otofuke-machi in Hokkaido, these white yolk eggs are known as kometsuya, which means 'rice luster' because in order to get the white color, the farmers feed their chickens white rice rather than corn meal.
Obviously corn meal alone wouldn't create a yellow yolk - other birds produce yellow-yolk eggs without the benefit of corn, but these farmers can change the usual yellow color to white by altering the chicken feed to an all-white rice base.
Apparently if one were to feed their chickens with white corn, the yolk produced would also be white.
While the quality of the grain fed to a chicken will affect the nutritional content of an egg, you can't tell just by looking at the egg. IE, the darker yolk does NOT mean the egg has more nutrients in it!
Also… a brown egg is NOT healthier than a white egg, racism be damned.
In other words, you don't have to pay more for one type of egg over an other - unless you want to ensure your eggs come from grain-fed hens in a cage-free environment.
Scientifically-speaking, yolk color is due to carotenoids, with the main source of carotenoid coming from the poultry feed's corn, maize gluten, alfalfa and grass meals - all of which contain pigmenting carotenoids lutein and zeaxanthin.
These two things combine with other oxygen-containing carotenoids, and are known as xanthophylls.
So… feed quality and consistency will affect the color of the yolk. To maintain consistency, farmers will yellow and red carotenoids like apoester and canthaxanthin to achieve the desired egg yolk color.
These supplements are eaten by the hen, transferred to the blood and then deposited in the yolk to provide the color.
As for our Japanese eggs… just because I hadn't heard of it before doesn't mean it's new.
Apparently these white yolk eggs have been available for years in Otofuke-machi, but it's only recently that it's consumption has been trending upwards enough for it to be a 'big deal' in Japanese media.
Truly poultry in motion,
Andrew "Sunny-side up"Joseph
PS: Thanks to Julien for the lead.