SWEETEN YOUR TEA?
The colour of your cup may do it
I steeped some green tea for five minutes in my bright red McGill mug using water filtered to reduce its mineral content. I then did the same with a white mug. Why? Because I had come across an episode of the BBC program Inside the Factory, that delved into the intricacies of making the perfect cup of tea.
The first bit of advice was to never drink tea from a foamed polystyrene cup because the plastic absorbs the flavour. That has some merit judging by the slew of experiments triggered by a physician’s observation back in 1979 that his foamed polystyrene cup had become soft after being filled with hot lemon tea. He was concerned that the tea was leaching chemicals out of the plastic and felt a need to alert the world to this risk. A number of scientists were quick to investigate with a consensus eventually emerging that instead of chemicals leaching out, limonene from lemon juice was being absorbed into the plastic, acting as a “plasticizer” to make the polystyrene more pliable. A British contributor opined that the whole issue was irrelevant because people who drink tea from a plastic cup deserve what they get. And what they get may, in fact, be less flavour since if the plastic can absorb limonene, conceivably it can also absorb flavour compounds from tea. So I’ll go along with ditching the polystyrene cup.
Removing calcium, present in water as calcium bicarbonate, also makes sense. The “scum” that can appear in brewed tea is caused partly by soluble calcium bicarbonate being converted to insoluble calcium carbonate and partly by calcium joining with catechins in tea to form a precipitate. It is these same catechins, epigallocatechin gallate (EGCG) in particular, that are often touted as being responsible for tea’s beneficial health effects, usually attributed to their antioxidant properties.
The extent to which catechins are present in the final beverage depends on how the leaves are processed. To make black tea, dried leaves are crushed to liberate enzymes that react with the catechins over a few hours to produce changes in flavour and colour. This is often referred to as “fermentation.” Green tea is not fermented, it is made by first steaming the leaves to halt any enzyme activity. Oolong tea is partially fermented. The highest concentration of catechins is therefore found in green tea.
It is always somewhat contentious to attribute health benefits to single foods or beverages, but researchers have pointed out that mice given green tea in their drinking water develop fewer tumours when exposed to carcinogens from smoke, and that the Japanese, who as a nation drink a lot of green tea, have a lower rate of lung cancer than North Americans, despite smoking more.
On the other hand, the International Agency for Research on Cancer (IARC) has classified drinking beverages hotter than 65 degrees Celsius as a cause of esophageal cancer. This was mostly based on epidemiological evidence from devotees of “mate tea,” brewed from the dried leaves of a small South American shrub and traditionally consumed at very hot temperatures.
According to trained physician and science educator Stuart Farrimond, the tea expert interviewed on Inside the Factory, the ideal temperature to consume tea is about 60 degrees Celsius, just about the temperature observed after steeping tea leaves for five minutes in water that was initially just below the boiling point. Five minutes supposedly maximizes the antioxidant content of the brew, as well.
Now about the colour of the mug. Farrimond claims that a red mug makes the tea taste sweeter. It has nothing to do with any chemicals leaching out of the mug, rather it has to do with the way the brain integrates visual information with taste. Some intriguing studies have indeed shown that taste can be affected by visual cues. Charles Spence and colleagues at Oxford University tested the influence of white, blue or clear glass coffee mugs on taste perception. Tasters judged coffee served in a white mug to be more intense than in a blue mug, while the glass mug provided the least intense flavour. On the other hand, the blue mug and the clear mug produced a greater sensation of sweetness than the white mug. In an experiment along the same lines, Spence’s group showed that hot chocolate tastes better in an orange or cream coloured cup than in a white or red one.
A literature search, however, did not reveal any study that backed up the contention that tea served in a red mug tastes sweeter. And neither were my taste buds able to detect any difference when they were treated to tea from different coloured mugs. But they sure detected a difference when recently I was served some iced tea in Virginia. Turns out that “sweet tea,” the popular southern beverage, has twice the sugar content of soft drinks! A calorie catastrophe that will make any nutritionist see red no matter what coloured glass or mug it comes in.