Something to chew on

Are you old enough to remember the Doublemint Twins? Or the introduction of Bubble Yum? Or young enough for the more modern Excel and 5?

Chewing gum is not new.

There is archaeological evidence humans have been chewing on gums, resins and latexes for thousands of years. The ancient Greeks chewed on the sap of the mastic tree. That's where we get the word "masticate" meaning "to chew."

The Mayans certainly used chicle, derived from the sap of the sapodilla tree, as a chewing gum. Further north, First Nations' people enjoyed chewing on spruce tree sap. I am told it is something of an acquired taste but that didn't stop John Curtis, an entrepreneur, from selling sticks of Maine Pure Spruce Gum in the mid-1800s.

Gums, resins and latexes are among the most common, most visible, and most interesting compounds produced by plants.

All plants produce them.

Scratch a tree and resin, in the form of sap, rapidly emerges. Cut a dandelion and a latex is exuded from the stem as a milky white liquid. If you run your fingers down the stem, you can squeeze out a large drop.

They appear to be some form of waste disposal, removing toxic substances from the plant, but they also serve as a weapon against predation by insects.

The holes insects bore into trees are quickly filled and covered by dripping sap. Fossilization of this sap gives us amber. The idea insects preserved in amber could still house DNA was the basis of the scientifically unsound movie Jurassic Park. But searching amber for insects tells us a great deal about past environments. If nothing else, it shows us plants have produced a variety of sap since the very beginning.

Latex, on the other hand, tends to have a milky texture, which means it doesn't generate amber. It is sticky and seems to have its effects through taste. For example, the latex of dandelions helps to imbue the plant with a bitter taste dissuading insects and other creatures from chewing it. Just ask any kid who has tried it!

On the other hand, if you collect dandelion latex between your fingers and stretch it back and forth, it quick turns into a gum-like material which can be rolled into a ball. Still doesn't taste very nice, though.

The reason this happens is gums are composed of long carbohydrate molecules called polymers - long chains of carbon, hydrogen, and oxygen bonded together. They're a little like a string of beads on a necklace, only many, many beads long. Typically, a polymer might run to thousands or even millions of atoms.

Latexes are similar in structure to gums. The major difference is the polymers are a little shorter and a little bit more water soluble in a latex. They also tend to have coiled structures which make them springy. They can be pulled out to their full length but they readily snap back. This provides them with their bouncy characteristic. Perhaps the most famous latex is natural rubber obtained from the rubber plant.

Chewing gum is made from a combination of latexes and gums. Historically, John Curtis's first commercial chewing gum was produced in Maine in 1848. The first patent for a chewing gum was issued to William Semple in 1869.

These original brands tried various alternatives to soften up the sap, including paraffin wax and petroleum residues. The addition of sweeteners - in the form of raw sugar - and flavouring agents led to improvements in chewing gums. But the big breakthrough in chewing gum technology came in 1869 when a young inventor by the name of Thomas Adams, started using chicle - the Mayan gum - as the source of latex. Flavoured with licorice or sassafras, it caught on quickly.

Many years and modifications later (including the sugar candy coating that makes chiclets chiclets) chewing gum is an international pasttime. Ironically, modern chewing gums contain very little gum. Some of the better ones still have a little latex - maybe 10 per cent - but, for the most part, the natural gums, resins, and latexes have been replaced.

Modern chewing gums are typically made from a combination of synthetic polymers such as styrene butadiene rubber (the stuff used to make car tires) or polyvinyl acetate, along with sugar and corn syrup.

Various flavouring agents and compounds such as sorbitol, which is a hydrogenated form of glucose that is just as sweet but doesn't have as many calories, are added to give us the multitude of modern varieties.

Some people might not think the compounds in chewing gum are the most appealing combination but they are chewy all the same and chewing gums keep evolving. Gone are the Doublemint Twins but now there is strawberry shortcake flavoured chewing gum.

What more could you want?