Lab Cat

13 Mar 2008

E is for…

Filed under: abc along, Basic Concepts, Food — Tags: , , , — Cat @ 5:00 pm
Easter Eggs

I love Cadbury’s Creme Eggs and have done since my first child minder, who used to work at Cadbury, brought me a half dozen of damaged or second creme eggs – you know the ones rejected for retail. I am cheating by showing Easter Eggs as the rest of this post is about hen’s eggs. Jennifer of The Spirit Trail also chose eggs as her ‘E’ and here is her lovely picture of her hens’ eggs:

eggs

Hen’s Eggs are amazing. Full of nutrients, especially protein, vitamins A, B and D and iron. The protein in egg has the highest protein efficiency ratio and is often used as the example protein as a comparison for other food proteins as it contains all the amino acids in the right ratio. More nutritional facts about hen’s eggs can be found at the American Egg Board’s website.

Eggs are very versatile. They can be eaten directly as boiled eggs, fried eggs, omeletes, scrambled eggs and poached eggs. Additionally the proteins in eggs can also be used

  • to help food set (e.g. egg custards),
  • as a foam to add air and volume (e.g. sponge cakes),
  • to clarify,
  • to give color,
  • as an emulsifier (e.g. mayonnaise).

The two different major proteins, egg white or albumin and egg yolk, respond differently to heat as they coagulate at different temperatures. Albumin starts coagulating at ~63 oC and yolk at 70 oC. The difference between their coagulation temperatures allows us to have cooked eggs with runny yolks. Egg yolks undergoing protein coagulation is the basis behind egg custards, including creme brulee.

For coagulation to occur the native protein first unfolds, scientists call this denaturation. As heat increases the proteins rearrange and eventually they coagulate or gel. This occurs with egg albumin when it turns from clear to cloudy white. This picture shows what happens when proteins unfold and then coagulate:

Coagulation

The Exploratorium has more information on the science of eggs including how to make a naked egg.

References:

Barham: The Science of Gooking

McGee: On Food and Cooking 2nd Edition

McWilliams: Introductory Foods

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1 Comment »

  1. Very interesting. Also, showing Easter Eggs is not cheating, as they are tasty. I like the carmel-filled ones myself, or coconut with dark chocolate.

    Comment by Lisa — 14 Mar 2008 @ 8:38 am


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