Now that I have done two medical-related reviews in a row, it‚Äôs time I review some research in another field.¬† For today‚Äôs post, I‚Äôve decided to review an article based on sensory perception and wine tasting.¬† A very common question I get while working in the tasting room is, ‚ÄúAt what temperature should I serve wine?‚ÄĚ¬† Does serving temperature really make a difference in regards to capturing the flavor of the wine?
The article I will review for this post addresses the issue of changing serving temperatures and perception of flavors in wine, in addition to perception of imperfections in the wine as the serving temperature changes.
The title of the article reviewed for today is:¬†
Influence of Serving Temperature and Wine Type on Perception of Ethyl Acetate and 4-ethyl Phenol in Wine; by M. Cliff and M. King
Up until this article was published, there had been very few studies looking at olfactory responses to aromas at different temperatures.¬† One study found that there was no difference in olfactory sensitivity with varying temperatures; however, this was later speculated to be as a result of the temperature of the sample equilibrating with body temperature, since the air entering the nasal cavity rapidly equilibrated with body temperature.¬† A later study found a more significant response, in that for beef flavor at varying temperatures, meaty intensity decreased with increasing temperatures, while vegetable intensity increased with increasing temperatures.
So what about wine?¬† Does the perception of flavors change in wine with changing serving temperatures?
The accepted serving temperatures for white wines range from 8-12oC (46-54oF), and 18-22oC (64-72oF) for red wines.¬† Frequently, people serve their white wines straight out of the refrigerator, which is often set in the mid-30‚Äôs oF, and serve their red wines at the temperature of the room they are sitting in (which if not in a wine cellar, is somewhere in the mid-70‚Äôs oF).¬† Does this difference in serving temperatures make a difference in regards to the flavor of the wine?
One former study found that variations in wine temperature change the relative proportion of headspace aromatics (in other words, changes the nose of the wine in the glass).¬† It has been speculated that changes in temperature could possibly enhance or suppress the detection of specific aromas in wine.¬† Some have attested that oak aromas can dominate in chilled white wines, while when the same wines are at room temperature, the fruit aromas are more pronounced and the oak becomes more integrated with the fruit.
The overall objective of the study under review in this post was to evaluate the effect of temperature on the perception of two compounds, ethyl acetate and 4-ethyl phenol.¬† When these two compounds are found in wine at higher levels, it is indicative of faulty or poor quality wine, or more specifically, increased volatile acidity and Brettanomyces (a yeast in wine that at low levels is fine, but at high levels has negative effects on flavor and quality).¬† In order to avoid methodological mistakes of the past, this study made special efforts to control and maintain the wine temperature, and to avoid any cognitive or psychological clues.
In my past few review posts, I‚Äôve not gone into great details of the methods; however, I will be more specific with this article, since I feel the methods were particularly interesting and helpful with your own analysis and interpretations of results.
Four wine blends, which were prepared from bottled British Columbia Vintners Quality Alliance commercial wines were used (Chardonnay, Gewurztraminer, a white blend, and a red blend).
The Chardonnay was barrel aged, so it had a strong oaky character.¬† The Gewurztraminer was very aromatic, with flavors of lychee, muscat, and floral notes.¬† The white blend was chosen to give clean, light fruit character.¬† The red blend was made from all Bordeaux grape varietals.¬†
Each of the four wines was partitioned into four equal volumes: 2 for control, and one each for the two compound treatments (200ppm ethyl acetate or 1000ppm 4-ethyl phenol).¬† These levels were chosen to be just above the threshold levels, so that they would be detectable by all of the judges, but not so dominant that temperature differences would not be detectable.¬† All of the wines and wine glasses were stored at the three different treatment temperatures (0, 10, and 22oC; or 32, 50, and 72oF) for eight hours before the study began.
The judges for this study were eight staff members (4 male, 4 female) from the Agriculture and Agri-Food Canada (Summerland, BC), who were chosen based on their availability, motivation, and previous sensory experience.¬† Tests were performed to be sure the judges could detect the ethyl acetate and 4-ethyl phenol in the wine, and they were able to practice until they were able to correctly identify which wines contained the added compounds.
Black 8-oz tulip shaped wine glasses were used, and were each individually wrapped with 1cm thick milar bubble film and secured with duct tape.¬† The glasses were placed in temperature controlled rooms set at the treatment temperatures (0, 10, and 20oC).¬† The milar film was tested for effectiveness at maintaining the desired temperature, and it was proven successful and maintained for a period of four minutes.
In each sensory evaluation session, one of each of the wine types was tested at each treatment temperature.¬† The judges took breaks in between sets of wine samples.¬† At each temperature, the base wine (control, no chemicals added) and the treated wine were evaluated in random order.¬† All wine types were completely randomized in their order of presentation to the judges, and were evaluated twice over the entire study.
The wines and wine glasses were stored at the treatment temperatures, and 30mL of wine were poured into the glasses just prior to the judges‚Äô arrival.¬† Each wine was evaluated within three minutes of being removed from the temperature controlled storage.¬† Glasses were covered with 6cm plasic Petri dishes, to avoid contamination of external factors.¬† The judges wore wool gloves and scarves to eliminate any thermal clues from the stems and rims of the wine glasses, and to act as a physical barrier from the cold.¬†
To evaluate, the judges swirled the glasses and held the glasses to their noses without touching their faces.¬† Judges evaluated the wines for intensity of fruit and volatile acidity (ethyl acetate) or intensity of fruit and Brettanomyces (4-ethyl phenol) on a low, moderate, and high intensity scale.
This study found that temperature was in fact a significant source of variation for perceived fruit intensity and perceived faults (i.e. ethyl acetate or 4-ethyl phenol) by the judges.¬† Wine-by-temperature effects proved NOT significant, meaning that each individual wine type shared similar responses to temperature changes.
The relationship between the perceived intensities and the temperature were linear for fruitiness (r=0.979; which if you‚Äôre unfamiliar with statistical analysis means that almost all of the variation of fruit intensity is explained by the temperature change!!), and ethyl acetate (r=0.980), in the ethyl acetate wines.¬† The relationship held the same as well for fruitiness (r=0.991) and 4-ethyl phenol (0.951) in the 4-ethyl phenol wines.¬†
The major findings of this study included the following:
¬∑¬†¬†¬†¬†¬†¬†¬†¬† The fruity components of the wines, as well as the added wine fault components, were more noticeable at higher temperatures.
¬∑¬†¬†¬†¬†¬†¬†¬†¬† The presence/addition of ethyl acetate and 4-ethyl phenol changed the response of the fruit intensity perceptions.
o¬†¬† The effect of added 4-ethyl phenol reduced the fruit intensity at all temperatures for all wine types.
¬ß¬† The magnitude of this effect was most noticeable in the white blend and Gewurztraminer.
o¬†¬† 4-ethyl phenol(i.e. Brettanomyces) significantly depressed fruit character.
The results of this study showed that the perception of the added wine faults, ethyl acetate and 4-ethyl phenol increased linearly with increases in serving temperature.¬†
In the control wines without these faults, the study showed that fruit intensity increased as temperature increased.¬† However, in the wines with faults added, the increase in perceived defect occurred even though there was an overall increase in fruit intensity.¬† Basically, the faults were stronger than the fruit intensity, and thus their presence negated an increased fruit intensity in the wines alone.¬† Therefore, it is speculated that the presence of 4-ethyl phenol (i.e. Brettanomyces) not only has its‚Äô own aroma, but also suppresses the much desired fruit character of the wine.
What does this mean for serving temperatures?
If there are faults in your wines, you‚Äôre more likely to notice them at higher temperature, due to their increased intensity and ability to suppress fruit character at higher temperatures.¬† I would imagine that one would be more likely to notice these faults in red wine, since as a whole, people serve them too warm.¬† For white wines, it‚Äôs a little more questionable.¬† Yes, if you serve them at a warmer temperature, you will be more likely to notice the faults of the wine if they are present, however, if you serve them too cold (i.e. straight out of the refrigerator), the flavor intensity is suppressed as well (though for a reason other than the wine fault).
So, what should you do?
If you are serving a red wine, and store it willy nilly about your warm house, pop it in the ‚Äėfridge about 20-30 minutes before you are going to drink it.¬† If you are serving a white wine, and have it stored in your cold refrigerator, take it out of the ‚Äėfridge 20-30 minute before you are going to drink it.¬† This will bring the wines to the temperature optimal for flavor intensity and minimal fault perception.¬†
Cliff, M.A., and King, M.C. 2009. Influence of Serving Temperature and Wine Type on Perception of Ethyl Acetate and 4-ethyl Phenol in Wine. Journal of Wine Research 20(1): 45-52.
I am not a health professional, nor do I pretend to be. Please consult your doctor before altering your alcohol consumption habits. Do not consume alcohol if you are under the age of 21. Do not drink and drive. Enjoy responsibly!