Science and Cooking by Michael Brenner

Author:Michael Brenner
Language: eng
Format: epub
Publisher: W. W. Norton & Company
Published: 2020-09-15T00:00:00+00:00

Let’s deconstruct the recipe: We are supposed to scoop ice cream into balls and then coat them, first in whipped egg whites, and then in crushed cornflakes. A photo of a cross-section of the finished fried ice cream ball is shown in (A). A diagram of the ice cream ball before it is fried is shown in (B). The cornflake coating is all we have to protect the ice cream from melting. Initially this outside layer is itself much warmer than the ice cream—the eggs and cornflakes are at room temperature, while the ice cream is frozen. If we put the ball in this state into the hot oil, it would hopelessly melt.

But there is a trick. The trick is similar to Nathan Myhrvold’s method for cooking a steak: Before frying, the coated ice cream ball is put back into the freezer—and left there for 3 hours. This is long enough so that when you take the ball out its temperature will be approximately that of the freezer, about – 18°C (0°F). When you place the frozen ice cream ball in the hot oil, heat from the oil starts diffusing into the cornflake coating and then into the ice cream. The temperature of the surface layer will gradually increase; after a relatively short time, it will reach the temperature at which the ice cream melts. As heat continues to diffuse farther and farther into the ice cream, more and more of the ice cream will melt.

Ideally, you would submerge your ice cream ball in the hot oil for just long enough to heat up the outer cornflake layer, turning it into a delicious golden crust, while leaving the ice cream still frozen. How long is just long enough? Well, the thickness of the cornflake layer in the recipe is approximately 0.3 cm. You can find this out by making the recipe yourself and measuring it; alternatively, you could estimate the thickness based on the dimensions of the ice cream balls and the amount of egg white and cornflakes in the recipe.

Either way, once we know the thickness of the cornflake layer, the question is how long it takes for heat to diffuse this distance. We can use our trusty equation to find out. Assuming that the rate of heat diffusion in ice cream is about the same as heat diffusion in water, we get:

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