Mountain Dew Zero Sugar redux

Hello dear readers. What a relief it is, when so many things that are happening around us clamor for our attention, that we can sometimes return to pleasant and diverting discussions of some of the more important things in life. A chief example for today being the ingredient lists for two beverages that I discussed the other day in this blog article, namely Diet Mountain Dew and Mountain Dew Zero Sugar. One commenter said this:

Read the rest of the label on both beverages – what is the artificial sweetener in Diet Mountain Dew and what else is in the Mountain Dew Zero Sugar? Those are the agents that affect the taste.

He’s not wrong that if two nominally identical beverages taste different from each other, it is often due to the use of different artificial sweeteners. In my own life the area where I run into this most often is the Diet Mountain Dew that comes from a soda fountain on the one hand, or the Diet Mountain Dew that comes from a bottle on the other hand. The thing is that the bottled Diet Mountain Dew uses aspartame as one of three sweeteners.  But aspartame does not have a very long shelf life. If you put a bottle of Diet Mountain Dew in a warm place for a couple of months, the aspartame will break down and stop being sweet. The beverage won’t taste normal any more. This is why the experienced consumer of bottled diet soft drinks will avoid purchasing too many months in advance and will instead try to purchase the bottles “just in time” to drink them. The experienced consumer of bottled diet soft drinks will likewise try to store the bottles at cool temperatures and not warm temperatures.

Which brings us to the fountain beverage version of Diet Mountain Dew. The maker of the fountain syrup is not able to make very many assumptions about the actions of the operator of the soda fountain. The operator of the soda fountain might store the syrup at room temperature or even at higher temperatures. The syrup might go for quite some time, perhaps weeks, before it gets used up. The pH of the syrup is usually neutral and thus is a higher pH than that of the bottled beverage, and the stability of aspartame turns out to be less if the pH is higher.

For all of these reasons, the maker of the fountain syrup will usually choose not to rely upon aspartame as the chief artificial sweetener, but will instead rely more on other artificial sweeteners that have longer shelf lives. A typical fallback choice for fountain syrups is saccharine. This is one of the reasons why the fountain version of Diet Mountain Dew tastes quite different from the bottled version of Diet Mountain Dew. I personally prefer the taste of the bottled beverage to that of the fountain beverage.

With this as background to the discussion, we return to the commenter’s question about whether perhaps the reason that Mountain Dew Zero Sugar tastes different from Diet Mountain Dew might be due to the use of non-identical artificial sweeteners?

So now we can turn to the two ingredient lists. Here they are:

Diet Mountain Dew	Mountain Dew Zero Sugar	function of the ingredient
carbonated water	carbonated water
concentrated orange juice
citric acid	citric acid	provides tartness
natural flavor	natural flavor
potassium benzoate	potassium benzoate	inhibits growth of mold, yeast, and some bacteria
citrus pectin	citrus pectin	thickening agent
aspartame	aspartame	artificial sweetener
potassium citrate	potassium citrate	pH buffer
caffeine	caffeine
sodium citrate		pH buffer
	gum arabic	thickening agent
acesulfame potassium	acesulfame potassium	artificial sweetener
sucralose	sucralose	artificial sweetener
	sodium citrate	pH buffer
gum arabic		thickening agent
sodium benzoate		preservative
calcium disodium EDTA	calcium disodium EDTA	preservative
Yellow 5	Yellow 5	food color

We can see several things about the two ingredient lists.

The sweeteners that are relied upon. As you can see the two beverages list the same three artificial sweeteners in the same ordinal sequence. This does not tell us the exact concentrations or percentages, of course, but it does tell us that in both beverages, the percentage of sucralose is less than the percentage of acesulfame potassium, and in both beverages, the percentage of acesulfame potassium is less than the percentage of aspartame. All of this suggests to me that to the extent the beverages taste different from each other, it might not be due to differences in the artificial sweeteners relied upon.

Thickening agents. For any diet beverage there is the problem that if there had been ordinary sugar in the beverage, the sugar would have served as a thickening agent. But the sugar is not there. So to get the same “mouth feel”, other thickening agents must be employed.  The usual choice is gum arabic and we see that this manufacturer indeed makes use of gum arabic. What’s interesting here is that as we know, Mountain Dew is a citrus beverage, made mostly from orange juice. Because it is a citrus beverage, a very natural choice for a thickening agent is citrus pectin. And indeed that is the chief thickening agent employed in these two diet beverages.

Tartness. One of the goals if you are going to make a citrus beverage is that it needs to taste tart. Citric acid is the ideal way to make this happen. The result is the beverage has a lower-than-neutral pH — the beverage is a bit acid.

pH buffers. In many aqueous solutions it is desired to provide one or more pH buffers. In the human bloodstream, for example, the chief buffer that is employed is a carbonate buffer. The carbonate ion can easily donate a proton or two, or absorb a proton or two, so as to counteract other things that might get into the bloodstream that might have pushed the pH up or down too much.

Another very handy buffer is the phosphate buffer. The phosphate ion is trivalent, as compared to the merely bivalent carbonate ion, and this means that the phosphate buffer has the chance to donate or absorb as many as three protons in its efforts to counteract things that might cause the pH in a solution to diverge too far from some desired level. Some soft drinks make use of a phosphate buffer.

The designer of these two drinks chose to make use of a citrate buffer, which is a natural choice once again given that the drink is desired to be a citrus drink. The citrate ion, like the carbonate ion, is bivalent so the buffer has the chance of donating or absorbing as many as two protons in its efforts to minimize divergence from the desired pH.

Calorie count. Diet Mountain Dew has five calories in a half-liter bottle. This compares with something like 250 calories in a same-size bottle of ordinary (non-diet) Mountain Dew. From my point of view five is close enough to zero that I pretty much ignore it. But the calories are there, and it is interesting to see that in the newer beverage (the Mountain Dew Zero Sugar) the calorie content is zero. I imagine that the “concentrated orange juice” in Diet Mountain Dew is likely the source of most of those five calories. They are probably ordinary sugar calories (maybe fructose) and the sugar probably helps to smooth over some of the harshness and aftertaste from the artificial sweeteners.

Indeed when I am at a self-serve soda fountain, I will usually fill my cup about ¾ or ⅞ of the way with Diet Mountain Dew and will top it off with ordinary (sugar-containing) Mountain Dew, with a goal of smoothing over some of the bite from the saccharine. A cocktail of the two beverages tastes better to me than the diet beverage taken by itself.

The flavor differences. Which brings us back around to the original question which is what might account for the flavor differences between the two beverages? The thing is that under FDA rules “natural flavor” can be a bunch of things lumped together and reported as if they were a single ingredient. For readers who make a living doing intellectual property law, it will be appreciated that this aspect of the FDA rules permits manufacturers to preserve trade secrets.  The formula for Coca-Cola, maintained in secrecy since the late 1800’s, is tucked away in the “natural flavor” item in the ingredient list for Coca-Cola.

The answer to the flavor difference question is, I suspect, due almost entirely to the non-identical mix of natural flavors in the two beverages (and of course the shift away from “concentrated orange juice” in the move to MDZS).

Caffeine levels. It is recalled from the previous article that MDZS has around 20% more caffeine than DMD. Yet the ordinal ranking of caffeine in the two lists is the same. This just tells us that there is a bit of spacing in the ingredient list above and below the caffeine position.