In the recipe for “cowboy coffee,” egg shells are used to clear the brew. How does that work?
Sunday, April 26th, 2009
Moe asked:
The recipe calls for several egg shells per gallon of coffee. They are stirred in with the coffee and somehow make the solids settle out so the coffee is clearer. I don’t think it’s the stickiness of egg whites — I think it has to with charge of particles.
I did a bit more research. Beer and wine are clarified using “fining” agents, which include isinglass (almost pure collagen made from sturgeon swim bladders), gelatine, various synthetics. Among the agents mentioned are egg white and, occasionally, egg shells. See the “Clarifying” section of.
The recipe calls for several egg shells per gallon of coffee. They are stirred in with the coffee and somehow make the solids settle out so the coffee is clearer. I don’t think it’s the stickiness of egg whites — I think it has to with charge of particles.
I did a bit more research. Beer and wine are clarified using “fining” agents, which include isinglass (almost pure collagen made from sturgeon swim bladders), gelatine, various synthetics. Among the agents mentioned are egg white and, occasionally, egg shells. See the “Clarifying” section of
The amounts used to clarify are slight — on the order 1/2 gram per gallon — so the amount of egg white clinging to the shells may be enough.
While it is not clear whether the shell or the whites are important, the universal factor in all the discussions of fining agents is charge. Suspended solids are often charged and the fining agents attract them so they can settle. So as best I can determine, that seems to be the mechanism. (Assuming of course, that it even works — while very often cited, we would need to test the theory!)