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A soft-drink company argued in a "dead mouse in a can of soda" case that an intact body of a dead mouse is unlikely to be found inside a can of soda because the dead mouse would have been dissolved by the acid in the soda can in that timeframe.

http://www.legalnewsline.com/news/227856-mt.-dew-mouse-would-be-jelly-like-pepsi-argues

  • The soda can was sealed in August 2008
  • The soda can was purchased and consumed in November 2009, according to plaintiff

Direction #1: bacterial decomposition of the mouse

  • The types of bacteria (anaerobic?) that can survive the packaging process - see "common question #1"

Direction #2: hydrolysis of collagen
(originally my focus, but now turns out to be the unimportant point)

Because the article does not include all of the details of that claim, we try to analyze it in several steps:

  1. By "jelly-like substance", was the veterinary pathologist referring to gelatin (hydrolyzed collagen)?
  2. Was the veterinary pathologist implying the complete dissolution of the dead mouse, leaving non-collagenous substances such as bones in the can?
  3. On the contrary, was the veterinary pathologist referring to partial dissolution of the dead mouse, which cause some tissues to disappear while the body still maintains its original shape?
  4. Or, was the veterinary pathologist expecting that some level of collagen / gelatin should have been detectable in the soda liquid?

The typical conditions for gelatin production varies, but it is notable that neither high pressure nor high temperature are necessary. However, this depends on the level of crosslinking in the collagen in the source material (the animal and the body part).

To summarize the conditions:

  • Normal boiling in a kitchen pot, without needing acid or alkali (just soup), for 10-24 hours, at atmospheric pressure (100 kPa)
  • Cooking in a pressure cooker, which typically rises to twice atmospheric pressure and 121°C (http://en.wikipedia.org/wiki/Pressure_cooking)
  • Commercial production often uses very high pressures (100MPa - 400MPa), but at much lower temperatures (from 10°C to 45°C)

Common questions:

  • Was the can subject to boiling temperature and higher-than-normal pressure during the packaging process?
    • This question will determine which direction is more likely. A sufficiently long boiling will kill most bacteria, although it is still possible for a very small amount of bacteria to remain. The boiling would have made the gelatin path more likely.
-3

Mountain Dew, the soda in question, is widely attested to contain phosphoric acid and have an acidity of pH=3.2 to 3.3.¹ A pH of 3.3 is a fairly strong acidity. The acidity of a liquid is a good predictor of its corrosivity (specifically, its ability to destroy body tissue). Even teeth can be dissolved; demineralization of teeth begins at pH 5.5.²

Barring actual tests of the effect of a pH 3.2 to 3.3 bath upon the flesh of a mouse, we must look for something similar. The safety data sheet for Mountain Dew is also not available, although presumably the bottling plants would have to make one available to employees.

A Draise skin test of a similarly acidic solution of 30% hydrogen peroxide in water (pH 3.3) gives a Severe result.³ The solution must be marked as Corrosive, Packing Group II for the purpose of transportation, meaning the liquid is known to cause full thickness destruction of intact skin tissue in less than 60 minutes. Similarly, a solution of phosphoric and hydrofluoric acid diluted to pH 3.3 is known to do the same. What will happen to the rest of the mouse over a > 1 year period I leave to your imagination.

But the effect we are looking for according to the pathologist's claim is not about the body tissue. It is demineralization of the mouse over a 15 month period: bones and teeth being dissolved, leaving behind a rather gelatinous, soft mass. For this purpose, we can look at a study published by the Academy of General Dentistry, which showed that tooth enamel (the hardest mineral tissue of the body) bathed in Mountain Dew dissolves at a rate of about 4.2% per 2 days. At that rate, the halflife of tooth enamel would be about one month. 99% of tooth enamel would be dissolved in 6 months.

However, and this is an important point, the acid in the can is a fixed quantity, and would be neutralized over time by the dissolved minerals, so the demineralization of the mouse would not be as rapid as predicted. The equilibrium point depends on several unknowns, but we can make a start on it. The mass of the acids in Mountain Dew is probably similar to the mass of the acids in many soft drinks. We know that Coca-Cola has about 0.055% phosphoric acid. Although there will also be citric acid in the product, we can use it as a conservative lower bound and assume that Mountain Dew has at least 0.2 grams of acids. If a skeleton is 10 to 20% of the weight of a 10 to 20 gram mouse, then you have 1 to 4 grams of bone to dissolve.

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    H2O2 and HF are not appropriate comparisons, their main effects are not due to their acidity but their other properties. Both are very dangerous to handle, H2O2 due to its strong oxidizing capabilities and HF due to its toxicity more so than its acidity. – Mad Scientist Jan 6 '12 at 9:01
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    Also, rather than telling the reader to do the research, do the Google search yourself and select an authoritative source for Mountain Dew pH, Hydrogen Peroxide safety sheets, etc. – Oddthinking Jan 6 '12 at 10:08
  • @Fabian: I would add that HF is a weak acid, but it is highly corrosive because of the very low electronegativiy of F. It is well known in fact to corrode glass. – nico Jan 6 '12 at 10:41
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    @Nico That was pretty much my point, though I shorted it too much in my comment. The special dangers of HF and H2O2 have nothing to do with their acidity, they are far more dangerous than an equally acidic solution of HCL or acetic acid for example. – Mad Scientist Jan 6 '12 at 10:43
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    Also - the whole point of the question is that the OP is skeptical that a 330ml of 3.3pH solution can dissolve a mouse. It's absolutely not obvious that leaving a mouse for a year will dissolve it. Is there enough mountain dew? Is it enough time? Those are the points you need to address here. All the rest tells us little or nothing about the outcome. – Sklivvz Jan 6 '12 at 11:48

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