The Perfect Egg

Imagine this, you sit down for breakfast and order some sort of ubiquitous poached egg on toast variation.  You anxiously slice the soft egg with your fork expecting a flow of warm golden goodness, but nothing happens… The yolk has been overcooked, the white is rubbery, and there is a slight sulfur smell emanating from your general area.  Everyone looks around to see where that awful smell is coming from.  You would probably be a little upset, but achieving the perfect runny egg yolk is actually more difficult than it seems.

8090167797_c851d5b172_k
Egg yolk starting to turn green, not very tasty. (RosieTulips on Flickr (cc by-nc-nd 2.0))

 

Protein

I’m sure you know by now that the egg is packed with protein.  Good for building your muscles and stuff, man.  But, did you know that not all egg proteins are the same, and therefore don’t behave equally with respect to heat and time.  There are 119 different proteins in the yolk alone. And besides, eggs are weird; they are liquid at room temperature and become solid when heated, isn’t that like backwards?  This happens when the proteins break down, or denature, when heated.  Imagine water molecules in the egg are a bunch of ping-pong balls and the proteins are bundles of yarn dispersed in the balls, as the temperature rises and the proteins denature, they become unraveled and tangle up the balls.  Eventually the water is forced from the egg as the proteins become more and more dense, a la dry gritty egg yolks.  Egg proteins start to denature, coagulate, and form structure at temperatures as low as 56°C, all the way to the last protein that coagulates at 80°C.

So, why do you even care?  Well controlling what proteins we allow to coagulate controls how the egg tastes, feels, and smells.  That last protein to denature is responsible for the rubbery unwanted texture of the hard-boiled egg whites and dehydrated gritty yolks.  Ergo, boiling water is way too hot to cook a tasty egg.  A well-cooked egg is heated only to the temperature corresponding to the coagulation of proteins that our tongue desires; in other words, somewhere around the 60°C -75°C range.

 

Creating the perfect egg

Maintaining a constant temperature on your kitchen stove is actually pretty hard, and besides, the difference between a flowing yolk and solid yolk is just 1 degree.  So how can you hold an egg at say 62°C until the yolk reaches thermal equilibrium?  The Japanese would cook eggs in their local “Onsen” hot spring where temperatures would stay pretty constant.

“Onsen Tamago” cooked in Japanese hotspring. Untitled by tetsu-k on Flickr (cc by-nc-nd 2.0)
“Onsen Tamago” cooked in Japanese hotspring. (Untitled by tetsu-k on Flickr (cc by-nc-nd 2.0))

 

Unfortunately, I don’t live in Japan. But in recent years with the new generation of chefs who strive for perfection, lab equipment is being incorporated more in professional and home kitchens.  This means that there is weird and intimidating equipment that can circulate water at a precise temperature.  These “immersion circulators” are now commonly used to cook food sous-vide, or in a constant temperature water bath.  Chances are you’ve eaten something cooked from one of these machines.

Quail eggs being cooked in a water bath. Picture by the author.
Quail eggs being cooked in a water bath. (Picture by the author)

 

Using an immersion circulator, I’ve set up a simple experiment with 6 eggs all cooked for 1 hour at different temperatures; as you can see, the texture of the yolk and white change noticeably from a difference of just 1°C per egg.

Eggs before cooking at labeled temperature. Picture by the author.
Eggs before cooking at labeled temperature. (Picture by the author)
Cracked eggs and broken yolks post cooking. Picture by the author
Cracked eggs and broken yolks post cooking. (Picture by the author)

 

Some things to note: the 60°C and 61°C are drastically different, this is because the 60°C egg was cooked after pulling the eggs from the refrigerator (started at a lower temperature) where the 61°C (and all eggs after) was cooked from room temperature. The yolk is liquid until the 65°C egg where the texture is like soft play-doh, the 65°C egg white is also noticeably more watery looking, this is because a certain protein in the white starts to coagulate at 65°C which happened to cling to the thicker white section (in the other eggs I was able to separate this protein from the white).

But wait, 1 hour for your breakfast egg?  Actually as long as you avoid the temperatures relating to the off-putting proteins you can cook an egg much faster and just as good. In fact I usually cook at 75°C for 13 min, which makes the white slightly more firm.

Try this amazing egg calculator to see the t/T ratio for your preferred egg texture, and give it a try.  I don’t expect anyone to have an immersion circulator but as it turns out a small esky is actually pretty good at holding water at temperature for a few hours, just start about 2°C above your final goal.

 

References:

On Food and Cooking, 2004, Harold McGee

Culinary Biophysics: on the Nature of the 6X°C Egg, 2011, César Vega, Ruben Mercadé-Prieto


18 Responses to “The Perfect Egg”

  1. Frenio Redeker says:

    Hm, unfortunately my favourite egg takes 17 minutes to cook… I will never have this much time in the morning and I have to cook it at a temperature of 72 °C.

    As an alternative to the immersion circulator I’d suggest a hotplate with a magnetic stirrer and a contact thermometer, but thats still not a cheap solution.

    http://www.ika.com/owa/ika/catalog.product_detail?iProduct=20002190&iCS=1&iProductgroup=188&iSubgroup=1

  2. jiaz3 says:

    My everyday breakfast must include egg, but I prefer fry egg because the temperature is easy to control and you can see what happens to the yolk.
    Anyway, really like this blog, we should pay more heed on our life to make something perfect.

  3. alexc says:

    Love anything to do with the science of cooking. Awesome post! I used to just deal with hard yolks, but you’ve inspired me to improve my methods.

  4. jrozek says:

    Thank you for the exceptionally detailed response. I’ve noticed the different bits of the white before but never paid much attention to it. Next time I try poaching I’ll follow your advice and not use vinegar. In the mean time I think I’ll stick to scrambling and frying- two things I have mastered.

  5. mmcmillan1 says:

    jrozek- I’m glad to be the residential egg expert, I’ll gladly accept that title hah. I’ve seen the vinegar trick before but haven’t used it much, I don’t poach eggs traditionally anyway. But the basic premise is to speed up coagulate in the outer thin white faster, for a neater looking egg. And I say thin white because there is actually 2 distinct types of whites, if you look next time you crack an egg, there will be a thicker white that surrounds the yolk and a thin white that is less viscous around the perimeter. If you use really good eggs (look at the egg grades link a few comments above) there will be more of the thick white and less thin so your eggs will automatically appear neater. You can actually remove the thin white if you crack the egg into a slotted spoon, the less viscous part will just flow through the holes. One other use for the vinegar is if you add salt to the water as well, the vinegar and bicarbonate react to form small co2 bubbles in the thin white as it coagulates, so when your egg is done it will float to the top. I wouldn’t use vinegar though, it actually produces an irregular film, almost skin like quality, on the outer egg due to the increase coagulation. The best option is to remove the thin white if you can, or just not worry too much about it!

  6. jrozek says:

    Some people swear by a splash of vinegar in their poached egg water. As the resident egg expert, do you know anything about it? It sounds like an old wives tale but my own experiments with/without it haven’t been very well controlled.

    Also you’ve made me crave perfectly poached eggs on avocado toast…

  7. mmcmillan1 says:

    Cheers, jsbarrow!

  8. mmcmillan1 says:

    Actually the egg grades are on the document page 21, electronic page 25

  9. mmcmillan1 says:

    lgstoney- good question and I’m not sure of the exact answer. There is definitely an obvious difference between egg yolk and egg white protein amounts mainly because the whites are 90% water and the yolks are just 50% so the raw egg difference there makes since. Based on the % of white and yolk sampled for “whole egg analysis” could bias the protein measurement in that regard. What doesn’t make since though is the different amounts based on say a fried egg and an omelet. But how does the USDA differentiate an omelette from a fried egg anyway? Are they both just eggs or must there be other things added for it to be an omelet? I use more yolks than white but some people use more whites, for example. Also, for the fried egg I would think the egg would be cooked for longer at a higher temperature, causing the egg to dry out and lose more of it’s water weight.
    Also, It could have something to do with the quality of the eggs. In the US we have defined grades, I’ve yet to see that in AUS but this picture (on page 25) represents the difference in grades well (http://www.ams.usda.gov/AMSv1.0/getfile?dDocName=STELDEV3004502).
    Basically if you start with the exact same egg and cook it at the same temperature for the same amount of time with no other additives (oil/butter) and sample the same ratios of yolk/white, the nutrients should be the same no matter if you fried it or scrambled it.

  10. jsbarrow says:

    This is unreal Malcolm,
    I will be sure to reference you when I happily out-science those pompous egg-know-it-alls 🙂

  11. lgstoney says:

    Cool!

    When I google “protein in egg” it comes up with a few different values, depending on the cooking style. For example: 16g for raw egg yolk, and 11 grams for omelet, both per 100g.

    https://www.google.com.au/search?client=ubuntu&channel=fs&q=protein+in+egg&ie=utf-8&oe=utf-8&gfe_rd=cr&ei=c6nyU7XVMcGN8QfI1YFY

    What’s going on here? I would have though it’d be the same amount of protein.

  12. mmcmillan1 says:

    tcouper- interesting idea, but I don’t think that would really stop the water from boiling, just slow it down. Most post are aluminum or even steel that has an already low thermal conductivity compared to something like copper (thats why copper pots are $). It’s more to do with your heat source and the liquid. Just boil you eggs in alcohol, might flavor it as well! Or cook on an induction top, but they still cant hold a steady temperature, better than open flame or electric stove though. Or cook on top of everest? Try inventing an anti-pressure cooker instead

  13. tcouper says:

    Great post Malcolm. I especially love the ping-pong ball/ball of yarn analogy as it made it easier to visualise what was actually happening inside the egg. Great to see you also demonstrated the difference between cooking an egg from a refrigerated temperature and an egg from room temperature. I was surprised with the contrasts. It might be a good idea to invent a pot that has a lower thermal conductivity which peaks somewhere below the coagulation of the last egg protein. Might be a good business investment…

  14. mmcmillan1 says:

    majer- You can buy them online, they are a little expensive but the prices have gone down recently as there is more companies causing competition. Check out Anova Culinary

    tonih- There is an app! it’s not very useful though and pretty boring, I actually haven’t used it in a few years. I’ve found it’s easier to pick a texture and use that t/T, then adjust based on what you get. The app is ore useful for cooking something like steak, where it can plot the temperature variation. But even then its not that great, much easier to stick a thermometer into it.

    asjones- The well poached egg always comes first in my book.

    togden- Ya try it out, If you start at 80 cook for about 10min and see what you get! cheers

  15. majer says:

    Very interesting post! Now I know how to cook the perfect egg! However, unless I have an immersion circulator it sounds a little difficult to pull off.
    Where can I find an immersion circulator and how much do they cost? I’ve never heard of them before.

  16. tonih says:

    This is awesome! I usually judge a good cafe by their coffee and their ability to make a good poached egg for my hungover brain. Is there something that you can get for your phone that helps you cook the perfect egg? Like an app or something?

  17. asjones says:

    Great post Malcolm, and thanks for all the egg-cooking tips! Since you seem like such an egg connoisseur, i was wondering if you had any insight on another post i read recently ,(http://blogs.unimelb.edu.au/sciencecommunication/2014/08/11/what-came-first-the-chicken-or-the-egg/) and could tell me which you think can first – the chicken or the (preferably well poached) egg?

  18. togden says:

    Malcolm! Having been disappointed too many times at restaurants when ordering my favourite, eggs benedict, I was all to interested in your blog post! I thought the experiment was interesting, I wouldn’t have thought such slight changes in the temperature over such a long time would effect the end result of the eggs, so thank you for putting in the extra effort! I think I’m going to have to try and keep my immersion circulator (AKA Esky full of water) below 80 degrees next time I make my eggs!