To the editors:
What a cruel day hath befallen when I, a lowly member of the teeming millions, must pen (word process?) a missive to the Great One [Cecil Adams] to inform him of the facts of science and how the world works.
To wit: The disintegration of chewing gum [The Straight Dope, September 4 and October 9] while exercising, eating butter or other food, extended kissing, or more expressive demonstrations of love or lust is not in the least mysterious, nor is there any need to call upon exotic digestive hormones, etc. Given time, normal saliva at body temperature is able to break down chewing gum. The oral cavity however is rarely at body temperature, being cooled by the passage of air from the lungs and nostrils. This is why you put the thermometer under your tongue and keep your mouth closed when checking for a fever.
The molecules in the chewing gum have an affinity for attaching to themselves. Since chewing is what you're normally doing when you have gum in your mouth the attack of the saliva is halted when the enzymes get knocked off as you chew. The enzymes can't attach very well at "low" temperatures (normal mouth temperatures) anyway.
Experiment: Leave gum on your dashboard while parking on a hot summer day with your windows rolled up. Start to chew the hot gum and it will immediately begin to fall apart, forcing you to spit it out. At high temperatures your saliva sticks to the gum as well as the gum sticks to itself.
Experiment: Chew gum while drinking warm (body temperature) coffee. The gum will start to fall apart. Now breathe through your mouth. The gum will regain its elasticity and reverse its decline.
Experiment: Chew gum for several hours after it loses its flavor. The gum will gradually lose its elasticity, and become stickier as the saliva breaks down the gum.
Experiment: Eat (just a little) of something greasy while chewing. The grease will interfere with the gum's sticking to itself, allowing your saliva to attack it.
Now to exercise, sex, etc. These individuals must have put old gum into a corner of their mouth or under their tongue and stopped chewing while otherwise occupied. This results in the gum heating up while being kept close to salivary glands and not being chewed. No wonder it fell apart. If Cecil Adams failed to cache the gum in his cheek it is clear why he and Mrs. Cecil were unable to replicate the earlier writer's experiment. Or maybe now they just don't get as heated up for as long as when they were first courting; oh well.
I hope the above is enlightening (if his previous protestations of ignorance were not a test of the gullibility of The Rest of Us). If you want to check me on this, or desire deeper knowledge, I would suggest you get in touch with a food chemist at Wm. Wrigley Co., Chicago IL 60611. I enjoy the Straight Dope column very much. It's always the first thing I read in the Reader, and occasionally the only thing. Keep up the fight against ignorance.
Product Development Manager
Medical Development Systems