While trying to figure out what makes certain beverages cloudy, Cornell researchers made the startling discovery that certain chemicals in green tea — and perhaps red wine — react with saliva in ways that can alter how we perceive flavors.

Specifically, regular consumption of the polyphenol-rich drinks can boost astringent sensations and our sensitivity to acids, reports Karl Siebert, professor of food science, Cornell University. Siebert also discovered that we all have varying levels of polyphenols already stored in our systems.

Siebert, who worked for 18 years in a brewery before becoming an academic, stumbled upon the finding while studying the relationship between polyphenols — chemical compounds found in plants — and protein chains in such drinks as beer and apple juice…

Siebert’s group discovered the strong effect of pH on haze formation, peaking at a pH level near 4. More acidic beverages like grape juice don’t get as cloudy. Higher pHs also lead to less haze.

These findings led Siebert to question whether the same thing happened in people’s mouths…

He then measured the polyphenol levels in saliva of people on days before, during and after they consumed several cups of green tea. This showed that saliva normally contains polyphenols, and there are large differences among individuals. Regular red wine and green tea drinkers had the highest levels. Drinking green tea was shown to elevate the saliva polyphenol levels.

“I would expect that red wine drinking would also, but we didn’t demonstrate this,” Siebert said…

“It appears that there is a metabolic pool of polyphenol that is influenced by dietary habits, and that the salivary polyphenol level influences perception of astringency caused by acids,” Siebert said.

RTFA. I’ll watch for an easily accessible copy of the original research – and the work that follows on from this study. Siebert thinks it may explain the “French paradox” – how they have a relatively low incidence of heart disease, despite their diet rich in saturated fats.