Here is a curious note. We eat eggs, lots of them. Fried, scrambled, omelet, boiled, etc. Our eggs are completely free range, and completely soy free, and mostly corn free, fed only organic grains and food scraps. The majority of their diet is from spending their days roaming the yard and pasture consuming everything that moves.
When we travel and are forced to eat breakfast in restaurants, it becomes obvious how different these farm eggs are from factory eggs. It always amazes the kids that factory eggs have yellow yolks. Chickens eggs do NOT naturally have yellow yolks! Instead they are bright orange. Yellow is a sign of a nutritionally deprived egg. But recently I noticed something else different about the eggs from factories served in restaurants.... they smell bad.
Hard boiled factory eggs have a distinctive sulfur smell. Careful cooking an lessen it to a great degree (don't overcook) but the aroma is still there. We noticed this more than ever this Easter when we bought some cheap factory eggs for coloring. The "egg smell" was overwhelming. But a few days alter when hard boiling our own natural eggs, there was virtually no smell a all. We have tested this several times with the same results. The conclusion - factory produced eggs smell bad when boiled. True free range soy free eggs do not.
This truly makes me wonder what is chemically different in the factory eggs. I am pretty sure it is from the commercial feed used to produce factory eggs, but cant be sure. Our chickens roam over a couple of acres of grass, bugs, and dirt in the sunshine and fresh air where factory egg chickens spend their life in little confined spaces full of noxious odors that are legally unhealthy for factory workers to breathe, fed commercially produced feed made of the cheapest ingredients available (mostly soy and corn, genetically altered to allow extensive pesticide use).
It could be the soy connection. I do not know the science behind it but I do know that feeding abundance of soy to chickens, even organic soy, produces different eggs than feeding a chicken's natural foods. The soy eggs are much more prone to trigger allergies, so they are obviously chemically different from natural eggs. (chickens do not naturally eat soy).
Bottom line, I don't understand this one, but can conclude that another difference between factory and natural eggs is that factory eggs smell bad when boiled, natural eggs do not.