Why does Dr Pepper (and its knock-offs) foam so much more than colas?

Factual Questions
1

At my house we buy whatever is on sale and contains caffeine, so pretty much every kind of soft drink on the market has passed through my kitchen at some point. Why is it that when I open a new bottle of Dr Pepper or Mr Pibb or any generic equivalent the darn thing foams up like Old Faithful? I’m always very gentle with it, because I know it’s going to happen, but it doesn’t help. I have to slooooowly loosen the cap a little at a time, with frequent frantic re-tightenings, before the pressure equalizes and I can pour my soda. I don’t have this problem with colas or 7-Up type drinks; with those I can merrily twist off the lid and pour away. Twist off a Dr. Pepper cap too fast and it’s Yellowstone in my kitchen.

I haven’t noticed this with cans, only plastic bottles. And it only happens the first time I open a fresh bottle. Are these types of sodas more carbonated than colas, or is it something in the flavoring that makes the CO[sub]2[/sub] more peppy? Or am I completely insane?

2

You’re insane (I don’t know how completely).

I drink virtually nothing but (diet) Dr Pepper, and the only time I have a problem with it is if I dropped the can or something.

Root beer, on the other hand, foams like a son of a gun.

3

But twickster, it’s

I’ve noticed it too, although not often, since most of the stores near me only have Dr. Pepper in cans instead of bottles.

4

I personally see this with Diet Pepsi in my area. The bottle foams up, and for the time that it is open, there is massive bubble flow from the interior surface of the bottle. Cap it up, and it stops as the pressure builds (part 2, I fully expect from my physics/chemistry classes).

I have always suspected imperfections in the type of plastic used for the bottles, as it doesn’t ever happen with Diet Coke (that I’ve found).

I do drink at least (1) 2 liter bottle per day, sometimes 2. (no, I’m not diabetic, just to pinch that hijack right away, discussed, tested, diagnosis found lacking in my case).

5

Yeah, you’re right – I should have said “only excess foaming if I drop the bottle.” I drink so much of this crap I drink out of both (bottles at home, cans at work).

The point remains, though, I’ve never noticed any particular problem with a regular container that hasn’t been shaken.

6

Well, here’s a random guess:

The Dr. Pepper and it’s knock offs were both bottled somewhere at a lower altitude. Therefore, the pressure inside the bottle has an even greater difference in your atmoshperic pressure than a bottle that was bottled nearby.

7

as another reference point, I drink Dr. Pepper, and my sister drinks Diet Coke. I’ve found that diet drinks have an amazing amount of foam, but I’ve never noticed Dr. Pepper having any more than Coke or Pepsi.
-Lil

8

Ah, see, I haven’t noticed this with diet drinks, but that’s probably because if it’s diet I don’t allow it in my house. Here’s what the Master has to say about that. I don’t think I’m crazy, I really have only noticed this with Dr Pepper and its ilk; does Dr Pepper have NutraSweet in it?