Emulating Starbucks Frappuccino Cream Base At Starbucks, the "Cream Based" (no coffee) frappuccinos all use a proprietary syrup base which I would like to emulate to be able to make a reasonable facsimile at home.

When the baristas make a "Vanilla Bean" frappuccino, the process goes something like this:


Add a measure of whole milk.
Add an appropriate measure of ice.
Add 3 pumps of aforementioned cream base syrup.
Add a few scoops of vanilla flavored powder.
Blend.


The milk/ice ratio I can play with, I've found a replacement for the vanilla powder that works well, but I'm stumped at re-creating the cream flavored syrup, which unfortunately, is absolutely key to getting the right taste and consistency.

I see some folks selling jugs of the stuff on ebay, which I can only assume is pilfered stock because Starbucks does not sell it retail. Fortunately, there are pictures of the ingredients label on the jug, which gives me a good starting point.

The image of the base is below.

The ingredients are listed as:


Water
Sugar
Salt
Natural and Artificial Flavor
Xanthan Gum (E415)
Potassium Sorbate (E202)
Citric Acid (E330)


I would like some suggestions for what kind of cream flavoring I should use to create my own. Whole milk powder? Coffee creamer? Something else?
I can't comment yet...but if I could, I might suggest using or swapping a portion of your sugar for liquid invert sugar, instead of caster or white granulated, in conjunction with the afore mentioned artificial flavorings, and possibly some more milk protien like sodium caseinate.  Invert sugar is often used in candies that must maintain a soft creamy liquid center (like those queen anne cherry bon-bon things), and I think it would positively alter the end-texture.  I bought some in Austin at a local cupcake/candy bakeshop that wasn't very expensive.(www.allinonebakeshop.com call them,  the website doesn't reflect all of the cool products they have). 

Hansson et al experimented with different sugar compositions for their beverages and noticed that there was a greater release of specific aromatic compounds using invert sugar. They posited that the glucose-fructose ratio that liquid invert sugar possesses, causes the water molecules to be more structred, thereby decreasing the amount of free water around.  Hyrophillic(water loving) flavors in the mix are then more concentrated in the available free water, waiting to be tasted. The hyrophobic( water-hating/fat loving) flavors like to stick with the fats, so using a very good emulsifuer to effectively distribute/suspend the fats through the rest of the mix will be important for the end flavor profile.
doi:10.1016/S0308-8146(00)00243-0

I might even add some turmeric to your mixture when you heat it (be aware of some yellow color transferrence), since the curcuminoids (bioactive ingredients in the turmeric rhizome/powdered spice) decompose into a few compounds like vanillin and ferulic acid when heated (longer the incubation = more vanillin as a result of its degradation). Here's one research paper doi:10.1016/S0731-7085(96)02024-9 I'm happy to provide additional peer-reviewed sources if desired.

One last thought on flavor additions...if you dont mind artificial, this is a gluten-free butter flavor:  http://www.shanks.com/product-category/extracts-flavors/imitation-butter/  It almost goes without saying, that only a VERY small amount would be needed(maybe a drop or two at most to really round out that creme profile).