What Is Gum?

My son loves candy. This really isn’t a surprise – we all do.  After all, the brain accounts for nearly 20% of our resting metabolic rate, and sugar is pretty much raw calories.  Not that he cares about any of that, mind. He just enjoys it because it’s sweet and tastes good.

He’s not so sure about gum, though. Mostly, I think, because you can’t actually eat it.  I think that’s what led him to ask, when he was given a whole pack of chewing gum, “dad, what’s gum?”

Uhm… rubber?  Or maybe it’s tree sap?  I remember something about something called “chicle” as well, I think. But to tell the truth, I’ve got no idea.

What is gum?

According to Wrigley, chewing gum is made of “gum base” – a statement that, although accurate, is not terribly informative.  Fortunately, the International Chewing Gum Association (ICGA) provides additional information:

1. What is gum base?

Gum base is what gives chewing gum its “chew.” It is made of a combination of food-grade polymers, waxes and softeners that give gum the texture desired by consumers and enable it to effectively deliver sweetness, flavor and various other benefits, including dental benefits.

2. What are polymers?

A polymer is a string of molecules (monomers) that usually contain carbon and hydrogen. Polymers are found naturally in the human body, animals, plants, and minerals. For example, DNA is a polymer, as are the proteins and starches in the foods we eat. 

Man-made polymers can be identical in structure to those found in the natural environment, but in many cases, these polymers provide guaranteed consistency, quality and purity that are not always found in some natural materials. This quality is particularly important for food-grade polymers used as ingredients.

3. What are food-grade polymers?

Food-grade polymers have been rigorously tested and have been determined to be safe for use in food. In chewing gum, polymers are what provide gum with its basic elastic properties. All polymers used in gum are food-grade and are legally permitted for use by international/national regulatory agencies, including those in the U.S., Europe, and Asia.

The most common food-grade polymer is Polyvinyl Acetate (PVAC Food Grade), a clear, solid resin that is also used in cosmetics and as a hair fixer.  It is water insoluable, but dissolves in acetone.

I suppose I could join the ranks of the tinfoil-hat-wearing alarmists who make a virtue of ignorance by proclaiming that you should only eat things you can pronounce, but I won’t. I will observe that, yes, polyvinyl acetates are also found in some glues and are used in bookbinding. But there’s a key phrase here:  “food safe”.  Food-grade PVAC meets FDA reequirements and is safe for human consumption. I don’t eat it, but that’s just because I don’t like gum.

Was gum always polymers?

It wasn’t always PVAC, anyway. Wrigley’s gives an overview of the history of gum (not surprisingly, given their professional interest…), pointing out that a number of cultures chewed tree resins to freshen their breath and help combat thirst. Modern gum starts with chicle.

Chicle is the juice of the Manilkara zapota, a tropical to subtropical evergreen in the Americas.  The juice is harvested and boiled to remove the excess water, forming a rubbery mass.

And the fact that it becomes a rubbery mass makes sense.  After all, chicle is a food-grade polymer – a polyterpene hydrocarbon nearly identical to rubber.

Can you eat it?

Not really, no.  It won’t stay in your gut for years -urban legends notwithstanding – but the human digestive tract can’t digest gum (whether made of polymers created in a tree or in a vat). It takes about a week to pass through you, and leaves the body in the usual manners along with all of the other indigestible things you consume.