This peppery note is an important element in one of Australia’s major wines, but winemakers can’t always predict when it will turn up, or how strong it will be. So scientists at the Australian Wine Research Institute sought to identify the chemical that creates it.
The Australian researchers did detect trace quantities of a peppery molecule in shiraz wine, but not enough to analyze it. So they looked for the same molecule in ground white pepper, and found it at levels of a few parts per million — enough to positively identify it as a chemical called rotundone.
Most white pepper comes from Indonesia, where peppercorns are fermented in water for up to two weeks to remove the fruit layer covering the seed. Black pepper (unfermented peppercorns with the fruit left on) has rotundone, but in much smaller amounts.
Perhaps because of its low concentration, nobody had noticed the presence of rotundone in pepper before. But the Australian team found that most people can smell rotundone at levels of parts per billion, making it by far the most potent aromatic in pepper, and a significant contributor to the aroma of shiraz.
The Australian researchers analyzed the rotundone content of shiraz grapes from six vineyards and two vintages, and had trained tasters evaluate wines made from those grapes. The rotundone content and perceived pepperiness were generally higher in 2002 than in 2003, and consistently higher in some vineyards compared with others. This suggests that plant genetics, vineyard management and weather all influence the pepperiness of shiraz wines. Further research should reveal how winemakers can control these factors to fine-tune the flavors of their wines.
Rotundone was originally discovered in the 1960s by chemists in India, who identified it in the tubers of a plant called nut grass and called it rotundone after the plant’s botanical name, Cyperus rotundus.
According to “Cornucopia II,” Stephen Facciola’s essential compendium of edible plants, fresh nut grass tubers have a strong flavor that resembles Vicks VapoRub. The Australian scientists found that high concentrations of rotundone smell “harsh” and “burnt.”
So an excess of rotundone may well be the cause of what the wine writer Jancis Robinson describes as the burned rubber quality in some Rhone syrahs. And it probably contributed to the inedibility of my mashed potatoes. The Band-Aid aftertaste, meanwhile, was one of the unpleasant undertones, from medicinal to manure-like, that are often produced when peppercorns are fermented to make white pepper. Black pepper is pleasantly aromatic by comparison, with a kind of woody freshness.
The Australian scientists may also have discovered how these highly spiced potatoes were allowed to leave the kitchen: they tested 49 people and found that about 20 percent of them could not detect rotundone at all, even at concentrations far above what’s found in white pepper. The scientists say this shows the different experiences two people can have of the same wine, or of the same pepper-seasoned food.
A thought inspired by these statistics and those unforgettable potatoes: maybe all restaurant cooks should be routinely tested for sensitivity to the basic seasonings. We don’t want the pepper grinder to fall into the wrong hands.
June 4, 2008
Copyright 2008 The New York Times Company