By W.Blake Gray for

Brettanomyces takes many different guises, researchers reveal.

The University of California, Davis, took a major step last week in the official academic overview of wine that smells like excrement.

“Fecal,” “wet dog” and “rotting fish” are three descriptors from a new aroma wheel, designed to help describe characteristics imparted by brettanomyces – a yeast which creates two volatile phenols that have distinctive odors: 4-ethylphenol (4-EP) and 4-ethylguaiacol (4-EG).

The wheel might help explain why some wine smells like sauerkraut or sour milk. But not all the smells on the wheel are bad. There’s also rose, cola, Chinese five-spice, mocha and a host of other aromas that have long been used as praise.

And that shows a major philosophical shift at UC Davis, which is the world’s foremost university for teaching clean, technical winemaking. While some winemakers in France have argued that brett can impart positive characteristics, UC Davis has been steadfast in leading the argument that brett equals bad. Its professors have always described brett as a “spoilage organism.”

Not anymore. ”There’s no denying that brett is part of many wines’ regional character,” said UC Davis professor Linda Bisson at a brettanomyces conference.

Bisson and UC Davis colleague Lucy Joseph confirmed what many winemakers have long speculated: that there are many kinds of brett, and some give characteristics that are mostly perceived as positive. Out of 83 strains of brett that UC Davis tested, aroma panelists regarded 17 of them positively.

But Joseph added that none of the positive judgments was universal; it just meant that more panelists liked those aromas than not.

“What you’re smelling is not what the person next to you is smelling,” she said. ”Everything you perceive is based on your genetic makeup and your background.”

For example, older Americans compare the compound 4EP to “Band Aids” because bandages once used a similar compound as an antiseptic. In China, different antiseptics were used.

“Chinese tasters thought the ‘Band-Aid’ character was Chinese 5-spice, and they liked it,” explained Joseph …