Exactly which fruit is Juicy Fruit gum supposed to taste like? Pineapple? Pear? Banana? Orange? All of the above? Sort of. But it doesn’t quite taste like any of these. Some quick googling brought me to a lively online discussion of the subject. There were a few uncertain guesses (“there’s definitely a banana-ish taste to it”), while others were convinced that it didn’t taste like a fruit at all (“It’s Juicy Fruit. I don’t know anything else that tastes like it” or “it tastes like yellow. It’s yellow-flavored gum”).
During my short career as a chemist I’ve come across a chemical called isoamyl acetate a number of times. It’s an unremarkable-looking clear liquid, but as soon as you crack open a bottle of it, you’re assaulted by the overpowering smell of Juicy Fruit. I like Juicy Fruit, so I think it’s a pleasant odor. (It smells a lot better than most things I’ve encountered in an organic chemistry lab anyway.) Of course I eventually began to wonder: maybe isoamyl acetate doesn’t just smell like Juicy Fruit, maybe it is Juicy Fruit.
It turns out that isoamyl acetate is widely believed to be the primary favoring agent used in Juicy Fruit. However, Wrigley, the gum’s manufacturer, won’t confirm this. Their website describes the gum’s taste only as a “one-of-a-kind flavor that satisfies your cravings for something sweet.” The ingredients printed on the back of the package aren’t much help either, listing “Natural and artificial flavors” as the only flavoring agents. Wrigley clarified this description only slightly in response to a customer email asking about the flavor of Juicy Fruit: “This brand is flavored with a combination of natural and artificial flavors, but I’m afraid we can’t be very specific because, for competitive reasons, we consider our Juicy Fruit flavoring formula to be a trade secret. I can, however, tell you that the mixture of fruit flavors in Juicy Fruit is comprised of predominately lemon, orange, pineapple and banana notes.” The flavor may be a trade secret, but if you’ve ever smelled isoamyl acetate, it’s not hard to put two and two together.
Wikipedia agrees, and isoamyl acetate is also a common bubblegum ingredient, but I should note here that there is some disagreement in the chemistry community as to which chemical makes up the principle flavor of Juicy Fruit. The other possibilities I’ve come across are isopentenyl acetate and isopentyl propionate, both of which are structurally very similar to isoamyl acetate (with an extra carbon here or a double bond there). It’s also possible that Juicy Fruit contains some mixture of these compounds.
Isoamyl acetate is sometimes called banana oil or essence of pear. Food manufacturers add it to foods along with other flavoring agents to impart a fruity flavor, and it’s synthetically manufactured on a large scale for this purpose. But it’s also produced naturally by a variety of fruits like apples, bananas, and pears as they ripen. Of course all of these fruits taste different, so isoamyl acetate isn’t solely responsible for their flavor. Instead, a complicated mixture of organic compounds produced by the fruits give rise to their unique flavors. The fact that isoamyl acetate is only one component of these flavors helps to explain why it tastes fruity to us even while we’re unsure exactly which fruit it tastes like.
Plants and chemists don’t have a monopoly on isoamyl acetate production. Oddly enough honey bees also produce it. You might think it would make a tasty addition to honey, but that’s not how the bees use it. Instead, when a bee stings something or someone, it leaves behind its’ stinger and releases a small amount of a mixture of isoamyl acetate and a few other organic compounds. Very small amounts of these chemicals disperse through the air and act as a call to arms for nearby bees, working them into a furious frenzy and drawing them to the site of the original sting.
Chemical ecologists first identified isoamyl acetate as a major component of the honey bee alarm pheromone in 1962, when they extracted the chemical from honey bee stingers. When the researchers presented caged bees with a cotton ball soaked in isoamyl acetate, the bees became agitated and were incited to sting the cotton. However, a cotton ball treated with actual bee stingers had an even greater effect, causing the bees to sting more frequently. It seemed that isoamyl acetate was only one component of the alarm pheromone. Later, chemical ecologists isolated nine additional chemicals from bee stingers, which, together with isoamyl acetate, make up the alarm pheromone. Even so, isoamyl acetate is the single biggest component, making up 27% of the pheromone.
So, could a ripe banana giving off isoamyl acetate fumes incite bees to attack? What about Juicy Fruit gum? Reports of Juicy Fruit related bee attacks are scarce or perhaps non-existent. A brief search didn’t turn up any accounts of bees stinging hapless gum-chewers. However, several commenters on a bee keeping forum did seem concerned by this possibility. Maybe chewing Juicy Fruit simply doesn’t release enough isoamyl acetate into the air to alert nearby bees. Then again, I think I’ll abstain from chewing Juicy Fruit if I ever find myself tending a bee hive.
The Making of Isoamyl Acetate
Juicy Fruit was the first gum that Wrigley manufactured, beginning way back in 1893. At that time the modern discipline of organic chemistry and the industrial-scale production of chemicals were just beginning to gain traction, but the synthetic process currently used to manufacture isoamyl acetate wasn’t discovered until 1895.
In the meantime, the most likely source of isoamyl acetate was whiskey distilleries. The yeast used to ferment grain into whiskey produces very small amounts of isoamyl acetate as a byproduct. After fermentation, the whiskey is concentrated and purified by distilling it several times. During these distillations, impurities like isoamyl acetate are collected separately from the bulk of the whiskey, usually at the beginning and end of the distillation.
The Wrigley company was founded in Chicago, and in the 1890s when they began making Juicy Fruit gum, Illinois was the whiskey capital of America, producing more than 18 million gallons of the liquor every year. Distillers would have only isolated tiny amounts of isoamyl acetate from each batch of whiskey, but considering the vast quantities of liquor flowing out of Illinois at the time, isoamyl acetate byproduct must have begun to pile up. And in Juicy Fruit, it seems that Wrigley may have found a way to use what was essentially a waste byproduct of whiskey distillation to make chewing gum.
A few years later a German chemist named Emil Fischer invented a general way to make isoamyl acetate and other similar compounds. He used a chemical reaction to stick two smaller molecules together. The process he invented, called Fischer Esterification, is still used to produce isoamyl acetate today. It consists of reacting isoamyl alcohol (an even more plentiful byproduct of liquor distillation or ethanol production) with acetic acid (also called vinegar when it’s diluted in water). It’s easier to access large quantities of isoamyl acetate using this synthetic process than it is to separate the stuff from whiskey, and at some point Wrigley probably switched to using isoamyl acetate produced through this process to make Juicy Fruit.
References and Further Reading
BOCH R, SHEARER DA, & STONE BC (1962). Identification of isoamyl acetate as an active component in the sting pheromone of the honey bee. Nature, 195, 1018-20 PMID: 13870346
Collins, A., & Blum, M. (1982). Bioassay of compounds derived from the honeybee sting Journal of Chemical Ecology, 8 (2), 463-470 DOI: 10.1007/BF00987794