Re: Why does milk wash down things like peanut butter best?

Great question!  Milk is a very complex substance and, even though it has 
been studied extensively over the years, it is still a mystery to most of 
us.  But, after a bit of pondering, I think the behavior you are seeing can 
be explained by a type of material in the milk called emulsifiers.  I 
wouldn't say they are the one 'special chemical' responsible but I think 
they are the main contributor.

To give you a very simple explanation - emulsifiers are ingredients that 
essentially facilitate the suspension of fats in water.  The presence of 
natural emulsifiers in milk helps keep the cream (milk fat) from separating 
from the skim portion.  My father used to tell me stories about the good 
old days when you had to spoon off the cream from the top of the bottles 
before drinking the milk.  But I digress...  The emulsifiers in the milk 
are important because they will be attracted to the fat in the peanut 
butter, coating the peanut butter in your mouth with milk.  The other 
beverages you are studying don't contain emulsifiers and won't exhibit 
similar behavior.

So, I would recommend you try to find some literature on emulsifiers.  I 
don't have enough information with me to give you any more specifics.  You 
might also want to think about whether the presence of the milk fat is 
having an effect on the 'ease of wash down'.  It could be fun to compare 
the peanut butter washed down by whole milk versus skim milk.

I hope this information helps!

Kieran