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If you are
beginning to experiment with sous vide cooking, then eggs sous
vide is a great place to start.
The egg is such a good experimental tool in part because it is
composed of the egg white and yolk which each contain proteins
which coagulate or harden at different temperatures. For example,
the different proteins in the albumen of eggs coagulate at temperatures
ranging from 141.8° to 183.2°F (61° to 84°C); just a few degrees
difference in cooking temperature will greatly affect just how
much the egg white solidifies. While Ovotransferrin begins to
set at 140°F/60C,
it only comprises 12% of egg white. The major protein of
egg white, ovalbumin, makes up 54% of the white and doesn't coagulate
until the temperature reaches 80 °C. The yolk begins to thicken
around 65 °C and sets around 70 °C.
The yolk
proteins begin to thicken at 65 °C and set at 70 °C. Further heating
to around 80-90 °C produces the crumbly texture typical of hard
boiled eggs. (McGee, Science of Cooking, pp 85) .
Several chefs
have claimed the perfect sous vide egg to be the 64.5 °C (148°F)
egg where both whites and yolk have similar consistencies. We
have found in our own tests that eggs still exhibit a runny white
while the yolk is more solid at temperatures of 147F (see photos
above and below).
| | | |  | |  | Sous
Vide egg at 147F (1hr)
Runny whites and sem-solid yolk | | Classic
8 minute boiled egg
Solid whites and runny yolk |
What temperature
are Chefs using for Sous Vide Eggs?
| |
Temperature |
Time |
Style |
| Joel Robuchon |
62.5 C |
4 hours |
in shell |
| Dan Barber |
62 C |
20 minutes |
in shell |
| Michael Eades |
64C |
45 minutes |
in shell |
| Heston Blumenthal |
73.2C |
20 minutes |
in pouch scrambled |
| Thomas Keller |
62.5C |
1 hour |
in shell |
| Grant Achatz |
82 C |
15 minutes |
egg, cream, salt in bag |
Egg White
Components:
Egg white
contains approximately 40 different proteins. Below is a list
of major proteins found in egg white by percentage, along with
their natural functions.
Ovalbumin
54% Nourishment; blocks digestive enzymes--Begins to set at
180°F/80C
Ovotransferrin 12% Binds iron -- Begins to set at 140°F/60C
Ovomucoid 11% Blocks digestive enzymes
Globulins 8% Plugs defects in membranes, shell
Lysozyme 3.5% Enzyme that digests bacterial cell walls
Ovomucin 1.5% Thickens egg white; inhibits viruses
Avidin .06% Binds vitamin (biotin)
Others 10% Bind vitamins, block digestive enzymes.
Egg Yolk
Components:
The two major
yolk proteins are lipovitellin (LV) and phosvitin (PV) --(HDL).
Lipovitellin is one of the two lipoproteins contained in hen's
egg yolk and comprises about one sixth of the yolk solid.
Egg Yolk
Composition
Egg yolk is
a complex mixture composed of granule and a water soluble fraction,
plasma. Each fraction contains a lipoprotein as the main constituent.
Granules contain mainly 70% high density lipoprotein (HDL), 16%
phosvitin and 12% low-density lipoprotein (LDL). Plasma is composed
of 85% LDL and 15% livetin.
| Proteins
(16.4%): |
Water
(48-50%)
|
Lipids
(32 to 34%) |
| plasma
: livetin & LDL (protein content ) |
triglycerol (66%) phospholipid (28%) including lecithin (has
remarkable emulsifying ability) cholesterol (3%, or 250 mg)
|
| granular
fraction: phosvitin (16%, carrier of Fe), lipovitellins
(70%) & LDL (12%) |
Note:
The color of yolk depends on the presence of carotenoids.
xanthophylls not carotene (Lutein and zeaxanthin) |
References
and Further Reading:
Eggs
- Getting Started with Sous-Vide
The Science
of Boiling an Egg
Quantitative
Analysis of Gelation in Egg Protein Systems
Food Resources
--Oregon State -- The Egg
How to prepare the perfect
boiled egg
On
Food and Cooking -- Harold McGee
The
Chicken egg yolk plasma and granule proteomes
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