To get chewing gum out of hair, peanut butter - or prob any cooking oil, depending on the ingredients of the gum - dissolves it.
Thus, any oil in the mouth will dissolve gum - the lipstick test would succeed if the brand were oil-based, perhaps, and I’ll bet some lipgloss would work better.
Chocolate has lots of oil.
I would guess some diets low in meat would create a less oily saliva - here I’m extrapolating…
I have experienced gum disintegration on a few occassions. It is a rapid process, one minute chewing normally, suddenly the gum goes granular and slimy and is not chewable and disgusting.
I typically chew the same brand of gum. Used to be Wrigley’s Big Red until they decided cinnamon had to be peppery, then I swapped to Orbit Cinnamint.
I didn’t do a detailed survey of what was occurring at the times, because it was unexpected both times I recall.
I typically chew gum for several hours. Usually it just loses flavor and then slowly becomes tougher until I give up chewing it.
Both times it fell apart in my mouth without warning. I was chewing and suddenly the gum went soggy, then became little granular bits and kinda slimy. Not chewable and definitely demanding to be spit out.
The first time I think it had been sitting in my car. This is not unusual for me, and doesn’t lead to gum disintegration typically, so I am curious why it would cause gum breakdown in 1 instance.
The other time involved a romantic setting. I have chewed gum in similar situations without gum breakdown.
I am currently sucking on my gum soaking in saliva, no chewing. 2 minutes and counting, no disintegration.
In Southern Louisiana, the temperature can get up into the upper 90s and the inside of the car gets up to around 140 according to my air-vent probe thermometer.
Wrigley’s gum always disintegrates in my mouth after it’s been left in a car on a hot day for any length of time. I quit leaving gum in the car long ago.
Upon 2 occassions I have tried to stimulate gum breakdown. I tried margarine and peanut butter.
Both times I chewed the gum for a significant length of time prior to testing - first time for ~ 6 hrs, second for a couple hours. No sign of disintegration prior to test.
Test profile was to take a fingertip of substance and apply to gum in my mouth, then proceed to chew.
First applied margarine. Other than getting the taste of margarine in my mouth, it did nothing to the gum. Zip, zilch, gum was normal. Both times the same.
Then applied peanut butter. First time, it did cause the gum to break down a bit, not quite full disintegration, but definite softening. Second was somewhat milder effect but again did soften the gum.
Neither contributed to the classical “disintegration” as experienced previously. Perhaps more peanut butter would have done so, but frankly I already had a fair sized dollop in my mouth, (~teaspoon?). I find it hard to imagine that if it takes that much peanut butter, that oils are contributing to the classical case described.