Eggs

Eggs are without a doubt the most common thickener used in the pastry kitchen. Long, tangly proteins are the source of their thickening power, which can bring the water flow around them to pretty much a complete stop. Though egg proteins naturally occur in small clumps, they can be convinced to un-clump with the application of a little heat or with some agitation. Once they’re unfolded they can be further convinced to bond at which point all manner of textures are possible depending on the degree of protein coagulation: a thick liquid crème Anglaise, a semi-flowing pastry cream, a fully gelled crème brûlée or a crisp baked meringue. All the cook must guard against is over-heating or over-agitating those egg proteins which causes them to completely coagulate, squeeze out the moisture that’s between them and form tough curds.

One of the most fascinating things about egg proteins is how manipulable their coagulation temperature is. An egg white starts to gel at a very low temperature indeed: 145 degrees Fahrenheit. It becomes firm at 150 and solid by 180. However by introducing other ingredients — such as dairy, sugar, fat and flour — we can raise all those coagulation points as high as several hundred degrees. Amazing, really. There’s so much that can be said about eggs. For now I guess I’ll keep it short!

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18 Responses to Eggs

  1. Jey says:

    Is there a difference in the coagulation process between pasteurized eggs and non pasteurized eggs? I found out that eggs in the US are always pasteurized while most other countries do not. Just wondering if this would change it’s chemistry a bit.

    I don’t know if I’m just imaging things or not, but I always thought that store bought eggs had runnier whites than the ones we got from farms and outside the country. (I guess it also could be the age of eggs too).

    • joepastry says:

      Hey Jey!

      Two very interesting questions. There is indeed a difference between pasteurized and unpasteurized eggs. Pasteurized eggs have been heated to a minimum of 130 degrees, but frequently more like 140-145 since it doesn’t take as long. At that point some of the proteins in the whites start to coagulate and once that process starts there’s no reversing it. That’s why pasteurized whites take longer to whip than non-pasteurized whites, for example. Does that help?

      And you’re right eggs from a country farm stand generally do have thicker whites. That’s a factor of freshness. With very fresh eggs the albumen (white) has a more neutral pH. In that environment the protein clumps that are present in the white cluster together creating thickness. As the egg gets older and the albumen becomes more alkaline, the protein clumps spread out, making the white thinner. This doesn’t affect the performance of the eggs at all. In fact it makes whites better for whipping!

      Thanks for the questions, Jey!

      - Joe

    • Jim Hu says:

      I don’t think it’s correct that in-shell eggs are routinely pasteurized in the US. If they were, you wouldn’t pay extra for the pasteurized ones. “Egg products”, which are anything where the egg is removed from its shell (per the USDA), must be pasteurized.

      • joepastry says:

        Great point Jim, one also made by Nicole. It;s very true, and I did not speak to that. Thank you,

        - Joe

    • Nicole says:

      Just to correct the record, US shell eggs are NOT routinely pasteurized! As far as I know, there’s only one company in the entire country that pasteurizes eggs (Davidson’s Safest Choice) and they’re not available nationwide.

      The US does clean the exterior of the eggshell, which I’m given to understand most other countries don’t, but your average carton of grocery store eggs is unpasteurized. The risk of salmonella poisoning from eggs is very low, but I’d hate for someone to make assumptions and accidentally serve someone who’s immunocompromised.

      • joepastry says:

        Very true Nicole, thanks for making the point. Pasteurized eggs are becoming more and more common here, but they are by no means the rule, so pasteurization can’t be assumed.

        The egg washing point is a good one. We in the States wash our eggs to get chicken excrement off the shells. Europeans don’t wash because the washing removes natural coatings which prevent bacteria from entering the egg through pores in the shell. Both solutions seem both right and wrong a little. Honestly I’m not sure where I stand on the issue. But thanks!

        - Joe

        • LML says:

          I prefer buying clean eggs with possible (invisible) bacteria to buying eggs with small splotches of poop and the stray delicate feather.

  2. Sally says:

    There are two other factors that can cause egg whites to be very runny: the age of the chicken and the heat in which the chicken started the process of laying. Older chickens (like some of ours) lay eggs with thinner whites. If the weather is hot, chickens drink more water, which also has an effect on the consistency of the egg white.

  3. Janelle says:

    Eggs as thickeners are super cool! I actually just wrote a post on egg yolks and how it holds mousse together.

    Much as I love custards, though, I think my favorite use of egg as thickener is folding a meringue into cake batter. It’s leavening for sure, but it also seems to bring a loose batter together.

    • joepastry says:

      Oh they’re multi-taskers, those egg thingies! I’ll look forward to reading your post, Janelle! Thanks!

      - Joe

  4. Dani says:

    I wanted to ask all along if you had considered the obscure whole egg pastry cream for the vanilla slice, but not doing so was much more in line with the respect students typically have for teachers. I needed to come up with a creative solution for something akin to the slice a couple of years ago and decided on a flan-like filling. Assembly was a little tricky but not impossible.

    • joepastry says:

      Wish you had said something, Dani, because that’s exactly what was needed. In the end I took Warren’s advice and included a variation on the filling that calls for whole eggs. I’ve honestly never worked with whole egg pastry cream before…now I shall seek it out.

      Please chime in whenever you feel like it in the future. I rely on my readers for help! ;)

      Cheers,

      - Joe

  5. naomi says:

    That eutectic stuff is just magic.

  6. NS says:

    Just wanted to mention that the egg in your photo is beautiful. I’m fortunate enough to have a source of eggs from a friend’s backyard chickens and (although the shells are brown), they always have that perky, bright orange yolk and very thick white.

    • joepastry says:

      Hey NS! Thank you very much! I love the look of fresh eggs as well. Makes me want to find a fry pan and some good butter! ;)

      Cheers,

      - Joe

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