A man in the U.S. is suing Pepsi Co. over a mouse allegedly found in a can of Mountain Dew, a claim the company rejects by saying the acid in the beverage would disintegrate the animal's body.

However, that reasoning doesn't hold water with Canadian food experts.

"There would not be enough acid in the matrix of the can to actually start causing those physical changes to the mouse," says Massimo Marcone, an associate professor of food science at the University of Guelph.

"The mouse would start to spoil; there would not be enough acid to preserve the mouse. It would start to smell bad. But to say that the mouse would actually dissolve in about 300 millilitres of soft drink, it’s pretty hard."

Pepsi made the statement in response to a claim by Roland Ball, an Illinois man who says he found a dead rodent in a can of Mountain Dew that he purchased in November 2009.

Ball is suing Pepsi over the incident, and the company has until Jan. 11 to respond to Ball’s amended complaint.

Pepsi argues that Ball’s claim is impossible. Using expert testimony from a veterinary pathologist, the company says the acids in the fizzy concoction would have turned the mouse's body into a "jelly-like" substance.

Mary Bamford, a registered dietitian in Toronto, is suspicious of the claim.

"When you think of the hair on the mouse, that's pretty tough to dissolve. The protein parts, in terms of everything on the inside [of the animal], would be a little more dissolvable in acid — that's what your stomach does, but it's of a pH that's much, much lower than pop."

Concerns over soft drinks

The only way it would be feasible, Marcone speculates, is if the offending rodent had been submerged in a larger tub of the liquid for an extended period.

"I could see it if the mouse was in a gigantic vat and had been there for a significant amount of time — with the amount of acids that are in there, over a longer amount of time, and because of course they would be flushing the tanks all the time with new acids, there is the possibility of [disintegration]," he says.

The controversy over the potency of Mountain Dew renews concerns about the chemical makeup of soft drinks.

"There are reasons why we encourage people to consume natural foods, and soda pop is one of those reasons," says Bamford.

In addition to predictable ingredients like sugar and carbonated water, Mountain Dew contains a mixture of food additives like citric acid, sodium benzoate and erythorbic acid, which enhance the taste and prevent bacterial growth.

What worries some consumers are countless stories about the other, unadvertised uses of certain soda beverages — most notably the alleged cleaning qualities of Coke.

"I remember the days of people cleaning the rust off their chrome bumpers with cola," says Bamford.

Urban myths

Marcone contends these are urban myths.

"If you look at a can of Coke, it has about a drop of phosphoric acid in the entire can. It's a very minuscule amount. They say that it will strip pennies, but it’s not enough to strip a penny — that's the problem," says Marcone.

Bamford nonetheless emphasizes that soft drinks contain "strong acids," and cites The A-Z Guide to Food Additives, published in 2009, which states that sodium benzoate, in combination with ascorbic acid and under the proper heat and light conditions, can produce benzene, a known carcinogen.

Marcone stresses that all of the ingredients in soft drinks are regulated by the federal Food and Drug Act, but concedes that your average bottle of pop is a delicate cocktail of flavours and preservatives.

Soft drinks are an example of what he calls "hurdle technology," a method in which chemicals work in tandem to control or eliminate pathogens in food products and ultimately prolong shelf life.

"Each individual component in there adds to the stability of the final product," he says.

"It’s a very delicate interplay of these basic ingredients. By putting in too much of one, it will put out of balance everything else — if you put in too much of one, for example, you’ll get precipitation and basically the beverage will go cloudy. You have to get it in the right concentration and the right order to be able to get the right properties of the beverage."

What's in Mountain Dew?

The ingredients list on Canadian Mountain Dew includes carbonated water, glucose-fructose and/or sugar, concentrated orange juice and vegetable oil. Some of the ingredients that might be less familiar to the average consumer include:

Citric acid: Present in almost all plants, and specifically citrus fruits, citric acid is generally used to add tartness to popular foods and drinks. It is also added to certain foods to improve their chemical stability in metal containers. Industrially, it is used as a water conditioner, a cleaning and polishing agent, and can be present as a chemical intermediate when ingredients are mixed.

According to Massimo Marcone, associate professor of food science at the University of Guelph, "Citric acid adds two things: flavour and it lowers the pH [the acidity or basicity] of the beverage."

Flavour: "Some companies have proprietary blends to make flavour, and they can be a combination of natural and artificial flavours," Marcone says. "As long as those flavours are permitted under the Food and Drug Act, they can add these as a proprietary mix to a beverage."

Sodium benzoate: "It's a preservative that is added to a variety of products," Marcone says. "Basically, it prevents the growth of bacteria and prevents the growth of fungus."

This salt-based preservative is widely used in salad dressings, soft drinks and jams, and fruit juices, as well as in medicines and cosmetics. Sodium benzoate is also used in fireworks in the so-called "whistle mix," the powder that produces the high screeching noise that fireworks can make.

Sodium citrate: This is the sodium salt of citric acid, and there are three members of the sodium citrate family — monosodium, disodium and trisodium citrate. It's used in foods and medicines as a flavouring agent (usually to add tartness), a chemical stabilizer and preservative. "It modulates the pH," Marcone says. "It acts a buffer, controls the level of pH and adds to the flavour."

Erythorbic acid: A vegetable-derived food additive produced from sucrose, erythorbic acid is widely used as an antioxidant in processed foods and also as a preservative in cured meats and frozen vegetables.

"It’s a type of vitamin C that’s added to control the pH," Marcone says.

Calcium disodium EDTA: Calcium disodium ethylenediaminetetraacetic acid, or EDTA, is added to foods as a preservative or stabilizing agent. In soft drinks containing ascorbic acid and sodium benzoate, EDTA prevents the formation of the carcinogen benzene. It is added to cosmetics to improve their stability when exposed to air.

"It’s a chelating agent — any metals that are found in there, it grabs onto them," Marcone says. "It sequesters any metals in the mixture, and keeps them from reacting with other ingredients."

Gum Arabic: Also known as acacia gum, meska, chaar gund or char goond, this is a natural gum taken from the acacia tree. It's used in food, as well as a variety of industrial and consumer products, including paint, textiles, adhesives and pharmaceuticals.

"This is a thickening agent, to give mouth-feel as you’re drinking it," Marcone says.