Questions we’ve all had about eggs

By: Eunice Jun

As you may have noticed, 2015 is looking to be a good year for eggs. In January, chemists from UC Irvine figured out how to unboil eggs, paving the way to cut production costs for cancer treatments and other sectors of the biotechnology industry. Then, the  Dietary Guidelines Advisory Committee declared cholesterol (ergo, the egg) may not actually be a menace to public health!

Chicken eggs are one of the most useful ingredients in the kitchen: you can eat them fried, in omelettes, hard-boiled, poached, or even baked. They also come in handy as ingredients. Eggs are used as thickeners and binders to improve the texture and structure of foods. They are great emulsifiers thanks to the lecithin in the yolks, making mayonnaise, ice cream, and other creamy delights possible.

Eggs are also a great source of protein at a low cost (although a new California law may cause an increase in egg prices). In fact, most Americans’ protein outside meat comes from eggs.  And they are also chock-full of nutrients! Let’s take a glance at the nutritional content of eggs:

Egg Nutrition



What makes a good egg? Well, as you can see from the image to the left, a fresh egg will have a compact white and centered yolk, both of which will be taller than their older counterparts. The air cell of an egg will be smaller the fresher the egg: this is why older eggs seem to peel better than fresh ones. To determine the freshness of an egg, you can put the egg in a glass of water. If it sinks, the air cell is small, so you have a fresh egg; if it floats, the air cell is larger, indicating you have an older egg. The difference between a fresh egg and an old egg isn’t going to be noticeable in taste, but a fresh egg has more desirable appearance, especially in preparing fried or poached eggs. The color of the yolk doesn’t significantly affect the nutritional value of the egg; rather, it is indicative of the diet of the chicken.

Now, there are a lot of misconceptions and questions about eggs that give them a bad reputation. Here are some fairly common concerns addressed in a simple, but science-based way.

When I eat eggs, am I eating baby chicks?  Eggs that you find in the grocery stores are not fertilized, so it is very unlikely that you are eating a baby chick. Moreover, even if an egg is fertilized, it needs a very specific environment to grow into a chick—and being in a refrigerator doesn’t really provide optimum conditions for that.

Is there a difference between white eggs and brown eggs?  Besides the color? Nope. Different breeds of chickens lay different colored eggs, with no difference in nutritional quality. There are species of chickens (Araucana) that even lay blue-ish eggs.




What about eggs labeled omega-3 eggs?  So these eggs are actually kind of cool. Basically, the diet that the hens are fed influences how much omega-3 fatty acids are found in the yolk. Feeding hens grasses, insects, flax, and canola seeds can increase the concentration of omega-3 fatty acids in the egg. One flavor downside to this is that sometimes the hens are fed fish oils, which can cause the eggs to taste a little fishy.

Can I get salmonella from my eggs/ is it safe to eat runny yolks?  Salmonella is a bacteria that can cause salmonellosis, an infection whose symptoms include fever, vomiting, and diarrhea. According to the USDA, salmonella can be found on the surface of shells as they pass through the chicken, since the egg leaves the hen’s body the same way it…well…the same way it poops. However, eggs are really cool in that their shells are porous, yet keep bacteria out: a mechanism developed to keep the growing baby chick healthy before hatching. Nevertheless, the eggs are washed and sanitized in processing plants for that reason.

Salmonella could possibly also be found inside the egg itself (1 in 20,000 eggs), which is why the USDA recommends not eating runny or undercooked eggs. Egg whites set at about 149° F and eggs yolks at 158° F. It is recommended to heat food containing eggs for at least ten minutes at 167° F. As you can see, this is above the temperature at which eggs set. It probably won’t kill you to eat eggs with runny yolks, but sickness is more likely in children, elderly, pregnant, and immunocompromised populations. If you’re really that worried, you can find pasteurized eggs at the grocery store.

So there you go! Eggs are nutritious, delicious, and useful for so many things. I’ll leave you with a lovely ode to eggs so you, too, can sing about how much you love eggs:


Charley, H., & Weaver, C. (1998). Foods: A scientific approach. Upper Saddle River, NJ: Merrill.

Naber, E. (1979). The Effect of Nutrition on the Composition of Eggs,. Poultry Science, 58(3), 518-528. Retrieved March 25, 2015, from Oxford Journals.

Scientific Report of the 2015 Dietary Guidelines Advisory Committee. (n.d.). Retrieved March 2, 2015, from

Ungerleider, N. (2015, January 5). California’s New Egg Law. Retrieved February 6, 2015, from

Weggemans, R., Zock, P., & Katan, M. (2001). Dietary cholesterol from eggs increases the ratio of total cholesterol to high-density lipoprotein cholesterol in humans: A meta-analysis. The American Journal of Clinical Nutrition, 73(5), 885-891.


Science Meets Food

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  1. Are there limits to how many eggs one can consume? if so are there any substitutes which contain similar nutritional contents(besides the obvious)?.

  2. do you think that eggs could be a menace to public health only when the incorrect was of preparing it is done or if there is maybe if hormones were to be injected in to the chickens are that would have a direct effect on the egg with is made by that chicken ?

  3. I have read that powdered eggs have exactly the same nutritional content as ‘normal’ eggs, and that because of the process there is no risk of salmonella. Is this true, or is there really no substitute for freshness when it comes to eggs?

  4. Very interesting article Eunice, it really opened my eyes to a lot of things i’ve been overlooking regarding the consumption of eggs. I was just thinking while reading this article about organic eggs versus inorganic eggs.
    I was wondering if you could clarify, if however possible, whether or not organic eggs are, actually more healthier that those produced through gene alteration.


  5. I’m beginning to wonder about the increase in posts authored by eight-digit numbers.

  6. I have a question, I cracked an egg and the yoke was clear white. This was a chicken egg and the rest of the dozen was normal.

  7. Some eggs are laid by female animals of many different species, and they are been eaten by humans. I was doing research for my blog about eggs and it brought me to your blog. I like the information you put on your blog for it is important and educational. Thanks for the nice information. Please get some information from my blog too. Thanks again for the nice write-up.

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