“Brett Character” in Wine: How Much Can the Experts REALLY Detect?

Among many in the wine industry, a wine exhibiting “Brett character” is generally thought of as negative and highly undesired in most wines.  This idea has been and still is a source of debate for some wine industry professionals, particularly when it comes to whether or not the presence of Brett is actually all that bad, or if it is just another added level of complexity to the wine.

“Brett character” is caused by the yeast, Brettanomyces bruxellensis, via several chemical transformations that result in increased levels of 4-ethylphenol and 4-ethylguaiacol in the wine.  A wine that has been contaminated with Brettanomyces is often described as having “off” flavors such as band-aid, barnyard, horse stables, and pharmaceutical, to name just a few.

On the other hand, some studies have found Brettanomyces to actually improve the sensory characteristics of a wine, including some leathery notes as well as improving the fruity and varietal aroma balance of the finished wine.

The ability to even detect Brettanomyces contamination is apparently difficult in and of itself, thus adding

fuel to the debate regarding whether or not the presence of Brett even matters.  One study found a very weak correlation between the levels of ethylphenols in wine and the detection of “Brett character” in the tested wines.  Another study found that the presence of other compounds, such as isobutyric and isovaleric acids, created a sort of “masking effect” that basically “hid” any Brett character that one would expect to be there based on the wine’s ethylphenol levels.  Yet another study found that even among wine experts, the ability to detect the presence of Brett is not universal—specifically, 1% of 134 wine experts had a diminished ability to detect ethylphenols or Brett character in wine.

One question that arises from this information is whether or not training and specific job type has any influence on the ability to detect Brettanomyces contamination in wine, or if the experts’ ability to identify this quality is completely random and irrespective of the type of training or job experiences they’ve had.  Is the ability to detect Brett characteristics in wine a learned trait? Or is it something some are just “born with”?

The study presented today aimed to address these questions by determining (1) the perception thresholds (i.e. how little of the stinky stuff can they actually smell) for wine experts, as well as (2) the language they use to describe the tainted wines and (3) the decision-making process utilized by the different wine experts (I do not go into this section at all, due to space limitations, but if anyone is really curious, I can look into it for a separate post).

Methods

A total of 87 participants were included in the analysis of this study, as out of the 206 that started the study, only 87 of them participated in at least two of the three parts of the study mentioned just previously.

The participants were determined to be wine experts with the following professions/experience:  winemakers, winegrowers, wine merchants, and wine brokers.  All participants were active in the

Bordeaux Wine Council and were involved in formal wine tasting on a regular basis.

Wines used in this study were red Bordeaux wines with bag-in-box closure systems, in order to avoid the possibility of cork taint.

In order to determine detection ability levels of each participant, wines were “spiked” with a serial dilution of ethylphenols from very high concentrations to very low concentrations (and everywhere in between).

“Spiked” wines were presented to participants at random along with two untouched “control” wines.  The participant was required to analyze all three wines and to determine which one of the three was different.  Individual detection thresholds were determined by the lowest concentrations of ethylphenols correctly identified three times in a row.

For the language/description portion of the study, the subjects were asked: “What terms would you use to characterize this sample?”. The frequency of use for each term among all the participants was calculated and analyzed.

Brief Results

Detection Abilities

• Wine expert profession had a significant influence on the ability of individuals to detect Brett character in wine, as well as off-odors in general.
• There was closer agreement among winemakers in regards to the detection of off-odors compared to all other professions studied.
• Variations in detection abilities among the individual participants were very large – specifically, the difference in ethylphenol concentrations identified was 2.5×10³ between the most sensitive and the least sensitive perceivers.
• Participants who were winemakers as well as those with academic tasting degrees were found to be significantly better at identifying Brett character in wines compared with other wine experts without academic degrees or in other professions.
• There were no effects of age on Brett detection ability in the participants in this study.

Language

• A total of 221 of terms were used to describe the contaminated wines, with 31 unique terms present.
• Odor descriptors used were always related to animal or pharmaceutical terms.
• There were no effects of age, profession, or academic qualifications on the terms used among individual participants.

Concluding Thoughts

Most studies that I read focus on comparing the ability of experts to detect a given characteristic compared with novices.  For me, this is the first time I’ve read a study focusing on within the expert group themselves, in order to tease apart some of the variation in tasting and detection abilities.  The results of this particular study, which when I thought about it make a lot of sense, indicated that wine makers as well as experts with academic degrees in tasting were better able to determine if a wine was “spiked” with Brett character, and were able to detect Brett characteristics at a much lower concentration than other wine experts of different professions.

If you think about it, this makes a lot of sense.  Winemakers taste many different kinds of wine ALL the time.  Specifically, they are tasting them earlier on in the process and can therefore attempt to make adjustments to allow the finished wine to be as “Brett-character free” as possible (I realize that’s not a real term, but you know what I mean).  Other wine experts, such as wine brokers and wine merchants, primarily taste the finished wine that’s had a chance to be manipulated already and thus by the sheer nature of their jobs, they don’t taste as many Brett-laden wines as do winemakers.  Additionally, a wine contaminated with Brett might not even make it to the market, giving the edge to winemakers again in terms of Brett tasting experience compared with other wine professionals.

Overall, this study provides some information regarding how wine experts perceive Brett character  in

wines, and helps illustrate why there might still be some debate in the wine community as to whether or not Brett is actually “good” or “bad” for a wine (not counting when it’s utilized on purpose).  Maybe those on the “good” team haven’t had enough experience with Brett to know what they are tasting?  Maybe it doesn’t even matter. If some wine experts are not able to detect a Brett-like fault in a particular wine, how in the world would the average consumer be able to tell?

In general, results like these in this study are interesting from a psychological standpoint and would be useful in wine competitions and judging, however, for the average consumer?  Just drink what you like, Brett-laden or not!

Feel free to share any of your thoughts/ideas/questions related to this short study.

Source: Tempère, S., Cuzange, E., Schaaper, M.H., de Lescar, R., de Revel, G., and Sicard, G. 2014. “Brett character” in wine: Is there a consensus among professional assessors? A perceptual and conceptual approach.  Food Quality and Preference 34: 29-36.