Can a dye or a label fool wine tasters?

Yes, they can, and the experiments are almost comic. When people know a wine's label, price, reputation or colour, those details can prejudice their judgment, so researchers hide them. Blind tasting means serving the wine without the taster seeing the label or bottle shape, sometimes in a black glass that masks the colour. Results from scientific blind tastings suggest the unreliability of wine tasting in both experts and consumers.

The most famous trick is attributed to the French researcher Frédéric Brochet. As reported, he served one mid-range Bordeaux in two bottles, one labelled as a cheap table wine and the other with a grand cru label. Tasters described the supposed grand cru as woody, complex and round, and the supposed cheap wine as short, light and faulty. In another test, a white wine drew the usual descriptions, fresh, dry, honeyed and lively. The same wine dyed red drew the usual red terms: intense, spicy, supple and deep.

A 2001 test at the University of Bordeaux shows the same pattern. It asked 54 undergraduates to taste two glasses, one red and one white. They failed to realise both wines were from one bottle: one had simply been coloured red with a flavourless dye.

Prices fool people too. In a 2011 double-blind test with 400 participants, Richard Wiseman found that members of the public could not tell expensive wines from inexpensive ones.

None of this means that nobody can taste. It shows that expectation is a powerful ingredient, which is why serious tastings hide the label.