The Hungarian tradition of plucking shrivelled grapes, sometimes one by one, to make pricey, sweet, white wine dates back centuries, but growers hope new technology will help them harvest the fruit at its rotten best.

Tokaji Aszu wine is one of a handful of wines around the world made with fruit affected by ‘noble rot’, induced by the Botrytis fungus that shrivels the grapes and concentrates their sugar.

One of the big Tokaj estates already uses sensors to measure humidity, precipitation and moisture on the vine leaves, data that, along with weather forecasts, can help predict common grape diseases, calculating the best time to spray the vines.

Those who try the aszu (shrivelled grapes) once will always feel that taste in their mouth

The same technology may soon be used to determine whether the grapes could reach the right stage of noble rot that is vital to making the Tokaji Aszu, favoured by the French royal court.

“The Botrytis fungus is an infection as well, one which we can turn to our advantage here thanks to the microclimatic conditions,” said Gergely Makai, winemaker at the Hetszolo winery, owned by France’s Michel Reybier vineyards.

The SmartVineyard system, developed in Hungary, allows users to access the data on smartphones or laptops.

“We have not tried yet, but we’d like this equipment and algorithm to help us predict sometime ahead how much chance there is for aszu grapes, for the Botrytis infection first of all, and then for it to induce a noble rot.”

Although technology is slowly intruding, the Tokaj region in the northeast of Hungary is a Unesco World Heritage site and, like the wine made there, is strongly attached to its traditions.

“Those who try the aszu (shrivelled grapes) once will always feel that taste in their mouth,” says Ilona Takacs, who will soon turn 70 and has worked in the vineyards for decades.

This year, when a hot summer was followed by a rainy period and then by warm, sunny days, promises a good harvest. Aszu grapes are picked by hand and, traditionally, pressed into the consistency of aszu paste, then fermented with white wine and aged in oak barrels for several years.

Legend has it that the first time Aszu was made was during Hungary’s Turkish occupation in the 17th century when the harvest was delayed until the grapes had shrivelled, and the infection set in.

While climatic conditions above the ground are critical, they are equally important below the ground in the deep, vaulted cellars, where bottles are kept, some for more than 100 years.

In the village of Tolcsva, government-owned cellars still hold some 280,000 bottles, the oldest of which are from 1895.

The special climate of the cellar – a steady temperature of 10˚C-11˚C and over 90 per cent humidity – has helped preserve them.

Laszlo Gardosi, in charge of the museum wines, says the oldest Tokaji Aszu he had tasted was from 1906.

“It was perhaps like an old man whose face bears the marks of age but still carries the elusive beauty that defined him in his youth,” he said of the experience.