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Fizzy chemistry, Got acne?, Soy-based sunscreen, Food that glows

January 16, 2006 | APPEARED IN VOLUME 84, ISSUE 3

Credit: Photo by Rachel Pepling
Credit: Photo by Rachel Pepling

Fizzy chemistry

An urban legend exists that eating Pop Rocks and drinking a carbonated beverage at the same time could cause one's stomach to explode. That legend is, of course, utterly false. Add a roll of Mentos to a 2-L bottle of soda, however, and you get a pretty nifty carbonated explosion.

Steve Spangler, director of the National Hands-on Science Institute and the "science guy" on 9NEWS KUSA-TV in Denver, demonstrates on his website ( that Mentos mixed with soda produces quite an impressive sight.

Carbonated drinks are fizzy, because under high pressure, water molecules trap carbon dioxide. When the pressure is released, say when a bottle is opened, some of the gas escapes. According to Spangler, the gum arabic used to make Mentos chewy also easily breaks the surface tension of water molecules, and the drink releases more carbon dioxide. As the candy dissolves, it forms nucleation pits where even more carbon dioxide bubbles can form. The result is a magnificent soda fountain.

Some tips for skyrocketing soda to impressive heights: go outside; use diet soda as it is less sticky and easier to clean up than regular; add all the Mentos candies at the same time; and invite the Newscripts gang to come play, er, help.

Got acne?

A study in the February 2005 issue of the Journal of the American Academy of Dermatology suggested that a high-dairy diet could contribute to teenage acne. In the December 2005 issue, however, dermatologist Harvey Arbesman offered a different hypothesis.

Arbesman, a dermatologist at the State University of New York, Buffalo, suggested in his letter to the editor that it's not the presence of hormones and bioactive molecules in milk that causes acne as the original study indicated. Instead, Arbesman suggests, it's the iodine levels in milk.

He points out that several studies have shown a connection between iodine consumption and acne development. Arbesman also mentions that studies have indicated high levels of iodine in milk in different countries, including the U.S.

But how, exactly, is iodine making its way into milkshakes? Arbesman says that fortified animal feed and sanitizing solutions are loaded with iodine. He's advised his own acne patients to cut back on dairy.

Arbesman does concede that his hypothesis needs further testing and measuring of iodine content of dairy products for validation. But his idea is udderly fascinating.

Soy-based sunscreen

USDA's Agricultural Research Service (ARS) announced on Nov. 3, 2005, that it has granted an exclusive license to iSOY Technology Corp. to produce a soy-based sunscreen. Based in Cary, Ill., iSOY has been working with ARS chemists Joseph Laszlo and David Compton to develop SoyScreen.

The natural sunscreen owes its sun-fighting power to ferulic acid, an antioxidant found in rice, oats, and other plants. The researchers used lipase enzymes and biocatalysis to bind ferulic acid to soy oil in order to prevent the antioxidant from dissolving in water. As a result, SoyScreen is swim- and sweat-proof.

According to ARS, SoyScreen filters UV light just as well as four commonly used synthetic absorbers: oxybenzone, dioxybenzone, octyl methoxycinnamate, and padimate-O.

Food that glows

Australians were a bit alarmed recently to discover glowing meat in their refrigerators. BBC News reported on its website on Nov. 16, 2005, that a caller to a Sydney radio talk show prompted the scare after reporting a "glow-in-the-dark pork chop" in his fridge.

George Davey, head of the New South Wales Food Authority, tried to counter speculation that glowing food might have been irradiated. He pointed out that irradiation of food is illegal in Australia. Instead, the glow was most likely caused by harmless Pseudomonas fluorescens bacteria.

The bacteria are often found on meat, and cooking normally kills the buggers. P. fluorescens is not known to cause food poisoning and tends to grow on seafood and meat that has not been stored at the correct temperature. Visible glowing indicates that the meat is beginning to spoil and should not be consumed. Davey says, "Remember this simple advice: if it glows, throw it!"

This week's column was written by Rachel Pepling. Please send comments and suggestions to



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