OK, here's a weird one (but I hope also a fun one). My girlfriend and I have noticed that the pastured eggs we get are thicker, or more viscous: when you put the eggs in a pan, the whites of one egg don't just run into the whites of another egg, but each one keeps its shape, separate from the others. Now, she told me that it is definitely the case that older eggs get runnier, including the yolk (and this is something you can take into account for cooking, so that you might use eggs of different ages for different purposes). But will the diet of the chickens affect the thickness of the eggs also? If we get eggs from a farm are they thicker just because they are fresher? Or does a properly-fed chicken produce thicker eggs (so that a pastured egg will be thicker than a non-pastured egg when both have been out of the hen for the same period of time)?
Has anyone out there noticed similar things? Do you have some data that could help answer the question one way or other?
If diet does affect thickness, are there any thoughts on the science behind it?
A weird question, I know, but I just can't deny my curiosity.
I agree with what has been said about the age of eggs, as that has been my experience. However I am certain that diet has a measurable effect as well. When my hens are eating lots of green grass in the spring, summer, and fall, the eggs are much more firm vs. the eggs from the same hens in the winter. As we tend to consume the eggs within a few days of them being laid, age can be ruled out as a variable.
My guess is that firmness may have something to do with the nutritional profile of the egg, and when the hens are pastured (and eating green things), that profile is superior. Check out this study conducted in 2007 by Mother Earth News regarding pastured eggs. vs. conventional eggs.
Hmmm. Well I've definitely noticed more naturally raised chickens have easier to crack shells. The eggs I get aren't exactly pasture raised. The chickens are kept in large cages covering the ground and get fed grain, greens, and table scraps. Uncaged chickens don't last long around here because of the coyotes. I get some eggs from our chickens and some eggs from the lady down the street. Other things, the yokes are brighter colored on the more natural chicken eggs, and we have a variety of types of chicken so I don't think that is it. I would agree that also the yokes do seem just a tad tougher and harder to pop on the more natural eggs, which is nice when you like your eggs cooked over easy like I do. I haven't really paid any attention to the runniness of the whites though.
Fresh eggs sit higher and stay together better. The older they get the flatter they sit.
The shell thickness is determined by whether or not they get enough calcium in their diet. I used to dry the eggshells, crumble them up, and feed them back to the hens. (If they got whole dried eggshells it encouraged them to peck at freshly laid eggs.)
The more greens they eat, the brighter yellow the yolks and the tastier the eggs.
I agree - fresh eggs have thick whites. The eggs from factory farms in grocery stores are often weeks old. I raise a few hens for eggs and their eggs have thick whites and orange yolks (so much so that when I have eaten hardboiled eggs at work, people have asked me what is wrong with them, lol). You can also tell a fresh egg from an old one if you hardboil then peel it. Fresh eggs are very hard to peel while old ones peel easily.
Joel Salatin mentioned this briefly in Michael Pollan's The Omnivore's Dilemma. He said his eggs had "tension" (or a similar word, can't recall exactly), where the yolk was much firmer and brighter.
I cook eggs sous vide all the time. I experiment across a range of 146°F to 150°F. I've noticed that the more politically correct the egg, the lower the temperature of yolk coagulation. This is probably due to different compositions of yolk proteins, etc. But there are confounding factors like egg age which are hard to control for across populations.
Has anyone else with an immersion circulator observed similar?
The eggshells are thicker! If a hen can do some exercise outdoors, get some daily sun, eat some bugs and be fed organic feed, it won't be on steroids and anti-biotic feed, plus it will produce a healthier egg. If it is not rushed and forced to produce eggs you will have eggs that are firmer. You are right about the content of the egg. They just look brighter and healthier. Amazing that we are so surprised by what good food looks like, eh?
Soyfed Eggs, avoid or no worries? 6 Answers
Eggs and cast-iron skillets 9 Answers