From Longman Dictionary of Contemporary Englishldoce_358_ayolkyolk /jəʊk $ joʊk, jelk/ noun [countable, uncountable] 
DFthe yellow part in the centre of an egg → white, albumen
DFthe yellow part in the centre of an egg → white, albumenExamples from the Corpus
yolk• Beat in egg yolks and vanilla.• They had an impression of very red cheeks and moist yellow hair smeared over the scalp like egg yolk.• With a mixer, beat the egg yolks with the bread mixture and garlic.• Whisk egg yolks and sugar in medium bowl to blend.• Beat the yolks into the milk sauce one at a time.• Who breaks the egg will find the yolk.• There is the yolk, the white and the shell.• The eggs had been microwaved, minus their shells, but with the yolks still intact.Origin yolk Old English geoloca, from geolu; → YELLOW1 