Is it possible to analyse an unlabeled sample of cola and determine whether it is Coke or Pepsi or something else?
Sure, just taste it.
:smack: I wasn’t thinking of that… but cola varies from country to country, and taste memory is unreliable (at least mine is). Can the test be made without anyone tasting it?
Well, it’s not like they’re going to put in a molecule that spells out “Pepsi,” so you’ll need known samples to compare against, but sure. They’re chemically different, so you could take them apart in a mass spec. and look at their signatures, or use other tools to examine them if you knew a particular chemical or ratio that was specific to one.
Easier, though, would be to shine a known light through them and measure it with a light meter: at least in my area, Coke is slightly lighter in color than Pepsi when strongly illuminated, and the diet versions of both are significantly darker than the non-diet ones.
I suspect (but haven’t tried) that if you were to dump yeast into “non-diet” cola, it would foam much more than if you dumped it into the diet versions – so there might be other “tricks” that could narrow it down.
Well, I can certainly taste the difference between diet and non-diet cola, but for something more dramatic, drop some Mentos in the cola. Diet Coke reacts more violently than regular Coke.
Coke has more Spice and Pepsi more citrus. Pepsi also has a little more sugar, although due to the way Coke is made is has a sweeter “mouth feel”.