Incredible Edible (Hard-boiled) Egg

By Sam Anderson and Eugene Hart

Objective

Calculating the time required to reach 160°F or 71°C in the center of the egg (safe eating temperature)Quiz #3 uses the thermophysical properties of

waterUse the thermophysical properties of an egg yolk

with the given geometry from Quiz #3Use the thermophysical properties of an egg yolk

with the actual geometrical measurementsBoiling the eggs for the calculated times to verify

To Determine if Quiz #3 is Accurate by….

Property ComparisonEgg ≈Water (Quiz

#3, r=1 in.)ρ=993 [kg/m3]cp=4178 [J/kg·K]k=0.628

[W/m·K]α=k/ρcp=0.15e-

6 [W/m·k]Bi=hr/k=16.2C1=1.95ς1=2.9r=0.0254 m

Egg properties1 (r=1 in.)

ρ=1131.74 [kg/m3]cp=2639.76 [J/kg·K]k=0.3985 [W/m·K]α=k/ρcp=0.133e-6

[W/m·k]Bi=hr/k=25.49C1=1.97

ς1=2.98r=0.0254 m

Egg properties1 (actual rad.)

ρ=1131.74 [kg/m3]

cp=2639.76 [J/kg·K]

k=0.3985 [W/m·K]

α=k/ρcp=0.133e-6 [W/m·k]

Bi=hr/k=23.2C1=1.97ς1=2.98r=0.0227 m

CalculationsApproximate Analytical Solution

Egg ≈Water (Quiz #3, r=1 in.)

Bi=16.2Tdone=160°F

or 71°CT∞ =21.39°C

Ti = 4.5°C

t(71°C)=17 min.

Egg properties1 (r=1 in.)

Bi=25.49Tdone=160°F or

71°CT∞ =21.39°C

Ti = 4.5°C

t(71°C)= 9 min. 6 sec.

Egg properties1 (actual rad.)

Bi=23.28Tdone=160°F or

71°CT∞ =21.39°C

Ti = 4.5°Ct(71°C)= 7 min.

48 sec.

The Experiment

84.6°C in the Center after 17 min. of boiling

The Experiment Continued

79.8 °C in the Center after 9 min. of boiling

The Experiment Continued

70.9°C in the Center! After 7.48 min. of boiling ≈71°C!

References

1 “Continuous Pastuerization of Egg Yolk: Thermophysical Properties and Process Simulation” by Gut, Pinto, Gabas, and Telis-Romero

http://www3.interscience.wiley.com/cgi-bin/fulltext/118650543/HTMLSTART

2 http://www.incredibleegg.org/?utm_campaign=-&utm_medium=cpc&utm_source=Google&utm_content=&utm_term=eggs&gclid=CJjM-beP36ACFQykiQodZHvD0A