Re: How does brining a turkey before smoking it make it juicier?

You're on the right track, but drawing the wrong conclusions.

The brine is absorbed by the meat. Your argument about drawing moisture 
out would only hold true if there was an excess of brine which supplied a 
reservoir for the moisture to move into.

In actually, meat proteins are made-up of amino acids, some of which are 
highly charged. They interact with the salt ions (Na+ and Cl-) in the 
brine to open their structure and to dramatically increase their water-
holding capacity. (The water interacts and hydrates the opened structure). 
The salt actually moves into the meat, and the extra water is also 
absorbed.

Now when you cook the turkey, the salt in the meat holds onto the moisture 
and so does the protein. Effectively, the equilibrium relative humidity 
(water activity) of the turkey has been lowered, so evaporation slows, 
everything else being equal.

To be more precise, whether the water goes into or out of the meat on 
soaking depends on the osmality of the salt solution. For some critical 
salt concentration, no + or - absorption of salt will occur. For salt 
concentrations above this, moisture will leave the meat and salt will 
enter. For concentrations below, salt will leave and moisture enter. 
Generally the migration of salt is much more important than the migration 
of water, since the salt has a profound effect on water-holding capacity.