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20-09-2020 06:07

Teveel proeven in recordtijd

Palatum vermoeid of toch aanstellerij?

Al vaker heb ik twijfel geuit over de kwaliteit van proefresultaten, die worden verkregen door tientallen wijnen achter elkaar te proeven met een halve minuut tussenruimte. Beïnvloedt de nasmaak van de ene het proefresultaat van de volgende niet, vraag ik me nogal eens af. Vooral wanneer ik in een internationale jury meer dan 100 wijnen per dag krijg voorgezet. Krijg je daar geen ‘vermoeid’ palatum van? En zijn je hersenen nog wel in staat de zintuiglijke waarnemingen scherp te registreren als je al tientallen wijnen hebt geproefd. Wetenschappers hebben zich daar ook al mee bezig gehouden.

Maar het probleem is dat niet elke proever hetzelfde palatum heeft. Vergelijkingen zijn dus moeilijk. Wie vaak jureert heeft nog het meest aan een glas water als mondreiniger. Rebecca Gibb is voor Wine-Searcher nagegaan hoe wetenschap en praktijk in deze aangelegenheid van elkaar verschillen.  


‘Palate fatigue


Last time you were tasting wine, did your mouth feel like it just did nine rounds in the ring?


That’ll be palate fatigue – a much-discussed topic that everyone has an opinion on, and which appears to be wholly subjective. Sounds a lot like wine.


So, how many wines can you taste in a day? Eighteen might be your limit, while some judges on the old-school Australian wine-judging circuit boast of tasting 300-plus wines on a single occasion. Unfortunately, tasting wine is not a competitive sport nor a measure of virility. Sorry to disappoint you, gents.


While there’s plenty of anecdotal evidence on palate fatigue, research is surprisingly scant. A trawl through scientific journals and a survey of some of the world’s leading sensory analysts drew a blank. There have been plenty of studies on palate cleansers – should you eat a cracker, drink water, chew wax? But no one’s broached the thorny question: when does palate fatigue kick in?


Carry over


So, what do we know?

In 1986, Dr. Jean-Xavier Guinard, currently a sensory scientist at UC Davis, found that tasters who had a break of 20 to 40 seconds between samples reduced – but did not eliminate – the "carry-over" effect from one wine to the next. Four years later, two other researchers (Lyman and Green) found that even with one-minute breaks there were large carry-over effects. In some cases, astringency in red wines can linger for up to six minutes before your palate is fit and raring to go. This suggests that a line-up of 20 or 30 reds at a wine competition, tasted in a relatively short time frame, can produce seriously flawed results.


Of course, waiting six minutes before tasting the next wine is not practical. At the Sydney International Wine Competition and many other wine shows, most judges have 30 seconds to taste a wine at the first pass, and those deemed to be “of interest” may get two to three more chances, explains competition organizer Warren Mason. Indeed, Ann Noble, the inventor of the aroma wheel and a former professor at UC Davis, believes that wine experts are aware palate fatigue occurs and mentally adjust their expectations.


“Winemakers often taste many wines sequentially with or without rinsing," says Noble. "Although they perceive increased astringency due to carryover, they can taste and smell other nuances fairly well.


Less wines


In practice, Noble suggests that the organizers of wine competitions should present fewer wines per entry class, and insist that judges rinse with water or use some other palate cleanser such as bread or crackers. A cleanser is defined as being effective "if it was able to reduce buildup and if it enhanced discrimination among samples,” according to a study by Lee and Vickers.


Cleansers are used in an attempt to reduce bitterness, astringency and sourness. Astringency is “a drying out and puckering sensation felt in the mouth,” according to the Society of Sensory Professionals, so we’re talking a combination of tannins and acidity here. The Society suggests that astringency “builds in intensity and becomes increasingly difficult to clear from the mouth over repeated exposures.” In other words, the cumulative effects of tasting wine mean that your palate ends up screwed.


But what to cleanse with? Scientists have provided us with a host of information on what to use, although research being research, what one study says is often countermanded by another.


The Lee and Vickers paper found that a glass of plain water is the best palate cleanser of all. And the added bonus is, it’s free. Milk has been tried without much success, along with xanthan gum, wax and bread. One team of researchers found that a viscose solution of carboxymethyl cellulose (CMC) or dry crackers were most effective. But the problem with some cleansers like CMC is that the viscosity of the rinsing agent can coat and lubricate the mouth, reducing sensations and leading to buffering effects on the wines.


Alternatively, could palate fatigue be a figment of our imagination? Perhaps it could be mental fatigue rather than physical fatigue, claims competition organizer Doug Frost, who is one of those rare beasts, a Master Sommelier and a Master of Wine.



Brain reacts


“I don’t believe the palate physically becomes fatigued unless you are drinking wines of a certain ilk, a certain intensity level, a certain sugar level," says Frost. "I think the biggest issue is the brain: the brain just becomes fatigued and you stop paying attention. With wine competitions, I make sure that people take breaks [and] get some air to change the brain a little."


Frost adds: "It’s not palate fatigue, it’s the inability to stop the noise in your brain and go: 'What’s in this wine, what’s this wine really about?'"


However, Noble is not convinced. In her view, "astringency ‘fatigue’ is a physical phenomenon in the mouth



Not reliable


How many is too many?

You wouldn’t run a marathon without doing any training unless you were an idiot. And tasting 150 wines in a day is not recommended for the uninitiated – nor is it any fun. But experts say that even hardcore tasters cannot produce reliable results if they sample more than a dozen wines in a session.


Leading sensory scientist Wendy Parr has undertaken extensive research on New Zealand Sauvignon Blanc in recent years. When tasting, she set an upper limit of 18 wines to avoid palate fatigue. Generally, says Parr, the ceiling is lower, and in scientific studies it is rare to see more than 12 wines tasted.


Yet that’s at odds with the procedures followed by both wine critics and wine competitions. Frost runs several wine contests from his base in Kansas City. “Typically we max out between 120 and 150 in a day," he says. "One year, I did a Sydney competition with [Australian winemaker and MW] Kim Milne, and we did 350 wines in a day.”


With so many wines, could he give each bottle its fair due? “No, I thought it was ridiculous. It’s not how you understand a wine and it’s not fair to a wine,” declares Frost.


He also admits that while he’s well-trained in the art of tasting many wines, everyone has both good and bad days: “There’s days when I fire into 175 wines like a monster and I’ve done a great job, and there’s days when I’ve done 75 wines and I think that I’ve missed some of them." Biodynamic-calendar followers might suggest that such disparities are all to do with root and fruit days.





Last and not least, we come up against the issue of "position order effect." In the sensory science world, researchers randomize the order of wines served to individual panelists, and often ask them to repeat the tasting with the wines in a different order. This is to mitigate the fact that each wine you taste influences your perception of those that follow.


It’s been suggested in some studies that wines placed early in a flight are preferred to wines that come later, for reasons that include fatigue and boredom. Other researchers claim that wines at the end of a series remain most vividly in the tasters’ minds and therefore have the edge. Whatever your conclusion, the placement of wines is a major factor in tasting wine, yet it is not taken into consideration by the majority of wine competitions.


It seems incredible that in 2013, we still don’t have any hard facts on when palate fatigue kicks in. It's true that a $64,000 question lies at the center of the debate; i.e. how can researchers obtain reliable results when everyone has a different palate? Perhaps it simply isn't feasible to get an answer. However, there remains a wide gap between the number of wines that sensory scientists recommend tasting in one session and the realities of the wine-show circuit. This is a gulf that needs to be bridged’.