Wednesday, November 25, 1998 Published at 12:25 GMT
No more flunking on dunking
Working it out: The formula for delicious dunking
People have long had to endure lumpy tea when their favourite nibble disintegrates to form a grey sludge at the bottom of the mug.
Their work is set to revolutionise tea and coffee breaks the world over, especially when a list of recommended dunking times is published.
The Bristol team calculate that up to 10 times more flavour is released this way than if the biscuit is eaten dry.
Their two-month investigation has also established the best strategy for dunking chocolate biscuits. The "flat-on" approach requires the nibble to be immersed biscuit side down.
This minimises "chocolate bleed" into the tea or coffee and keeps the coating rigid enough to prevent the biscuit from breaking in half.
Dr Len Fisher, who led the research, said a biscuit could be viewed as lumps of starch glued together by sugar.
When the hot tea or coffee enters the pores in the biscuit, he explained, the sugar melts and the structure becomes unstable.
"You have got a race between the dissolving of the sugar and your biscuit falling apart and a swelling of the starch grains so that they stick together, giving you a biscuit which is purely starch but rather softer than what you started with," he said.
"As with most things in physics, we can write equations which govern this."
Dunk with confidence
Aware that some people may have problems with their maths, Dr Fisher plans to give people more user-friendly information.
"We are going to define critical times for different types of biscuit," he said.
"We will publish these as a table, you will be able to look them up and you will be able to dunk scientifically with confidence."
"I suggest for serious dunkers, take a thermometer with you," he said.
The research has been funded by the biscuit manufacturer McVitie's.
The company says its own research suggests that one-in-four dunks results in soggy biscuit sinking to the bottom of the mug. It may now print advice for consumers on its packaging.