I had a minute and went and picked up this from a Dr. Pepper FAQ :
http://faqs.org/faqs/drink/dr-pepper/
There were differing opinions on wether DrP came from 23 fruit flavors or the following, but I find the following believable. And quite possible to be fermentable.
Quoting:
Max Wolheim (
[email protected]), who "can't guarantee the accuracy of
any of this," posted this interesting article (with a small caveat) on
June 20, 1999:
Yes, I've heard the "23 fruit flavors" of Dr. Pepper [sic] for years.
I can tell you this is nonsense! I can't reveal the source (he'd get
fired), but here is a list of some of the real flavoring ingredients:
Vanillin (imitation vanilla)
Extract of almond
denatured rum (no joke)
Oil of orange
lactic acid (optional; once listed separately from
"flavorings")
Max goes on to say: "None of this is will be confirmed by the PR
people of the company, who reply with the evasive 'Dr. Pepper contains
neither rum nor vanilla.' Substitutions are possible, depending on
the bottler, so that Dr. Pepper in one part of the country might not
taste quite the same as in some others. But denatured rum is
universal to the formula." Take it for what it's worth.
End Quote
I don't have rum on hand to mix this up and see what flavor comes out, but it seems to support the amerreto theory.