Eggsperiments!

Part I: The Incredible, Edible Egg

Spice of Life Class 8, Fall 2012

Student Learning Goals:

After completing this session of Eggsperiments, students will be able to:

  1. Describe the relationship between the structure and the function of a protein.
  2. Discuss the various ways in which proteins can be denatured in the kitchen, and the impact of denaturation on protein structure and function.
  3. Describe the different biochemical components of the egg, and how cooking impacts each of them.
  4. Calculate the amount of time necessary to boil an egg to a desired level of doneness, given a variety of egg sizes and water temperatures.

VI. Proteins

A. Amino Acids and Peptides

1. Amino Acid Structure

2. Protein Structure

3. Protein Function

4. Protein Denaturation

5. Effect of Denaturation on Protein Structure and Function

Eggsperiments!

Now that you know about the scientific principles that underlie cooking by convection and conduction, and how protein structure is affected by cooking, it is time to put all of that hard-earned knowledge to practical use. That is, you will now learn how to make the perfect boiled eggs. Before you can do that, however, we’ll need to take a look at egg structure.

The Anatomy of an Egg

Biochemical Composition of the Egg Yolk:

Biochemical Composition of the Egg White:

Cooking an Egg:

In the book ‘The Science of Cooking”, Peter Barham derives the following formula for cooking an egg initially at a temperature of T0, and with diameter of d mm:

In other words, the time it takes to boil an egg in water really depends on the volume of the egg, the temperature of the egg, the temperature of the water, and the final

temperature you desire for your yolk. As you have now learned, that final temperature is all-important, not only for safety, but also for taste, texture and appearance. The problem with this formula is that it does not always seem to work…so let’s see how we do this year!

Procedure:

  1. Each group should get 2 eggs. Note that they have been stored on their sides (to keep the yolk centered) and that they have been warmed to room temperature (to help keep them from cracking).
  1. Turn on your electric burners, and place water in your pot.
  1. Take the temperature of the room, and convert it to °F

Formula: °C = (°F-32) x 0.56.

  1. You will be using the table below for all of today’s cooking calculations, so go ahead and convert all of the temperatures in the first column to °F, and write them in the table below, and in the appropriate part of the Eggsperiments worksheet that follows.

Temperature / Effects on Egg White / Effects on Yolk
Below 55°C / Risk of Salmonella
57°C / Eggs held at this temperature for 75 minutes are considered to be Pasteurized
62- 63°C / Ovotransferrin begins to denature
Soft and gelatinous texture / ‘Runny’ liquid
62-65°C / Most egg white proteins begin to denature / Egg yolks still runny
65-70°C / Set as a soft gel / Still runny, but liquid starting to thicken – Most egg yolk proteins begin to denature at this temperature
73°C / Hardening of white, texture of soft fruit, strawberries, etc. / Soft, gel like texture rather like a thick shampoo
77°C / White continues to harden / Hard-boiled still soft, but solid texture of set yoghurt
80°C / Ovalbumin denatures / Onset of green discoloration around edge of yolk
90°C / Overcooked tough white, texture of damp sponge / Yolk completely dry, crumbly solid, quite a bit of green
  1. Measure the diameter of each of your eggs. Record the values in the Eggsperiements table in the worksheet.
  1. You will initially be hard-boiling your eggs. A hard-boiled egg’s yolk has reached 73-77°C all the way to the center, but has not yet turned green! Calculate the time that this will take for each egg and record the value in the Eggsperiments table.
  1. When the water has reached 100°C (212°F), place one egg into the pot. Try to monitor the boiling so that it is not too vigorous, but does remain at 212°F/100°C. Cook the egg for the amount of time that you calculate, then place it quickly into cold water. This keeps it from cooking any further, and makes the egg easier to peel.
  1. Cool the egg for 10 minutes.
  1. Carefully remove the shell from your hard-boiled eggs and observe them. Did they cook as you expected? Enter the answer in the Eggsperiments worksheet.
  1. If so: then go ahead and try to make a soft-boiled egg, or see if you can make the egg green. Write the appropriate ‘style’ (green, soft-boiled, etc) in the table, show your calculations in the worksheet, and then cook the egg.

If not: then try again, adjusting the timing. Write ‘hard-boiled’ in the space in the table, and give the new cooking time (calculations not needed).

Recipe for Deviled Eggs