Friday, December 21, 2007

How to tell a wine is spoiled? – Part 2

With increased interest in wine spoilage, I thought it is timely to give a brief overview on how to determine if the wine is of good quality and if it is spoiled. The basic steps in assessing a wine are as follows: Appearance, Nose and Palate. This is generally applied to a wine that has been poured into a glass and the drinker will focus on these three aspects of the wine. However, when you are in a restaurant or at your own home hosting a dinner party for instance, it may be a little late to figure out if the wine is spoiled after pouring it into the glass. After all, you do not want to be seen serving bad wines. So, there are some simple observations prior the standard 3-step assessment technique.

First, before removing the bottle seal, observe the general appearance of the bottle. If there are wine stains originating from the opening of the bottle, especially if the seal is damp, we can almost be sure that the wine has been exposed to oxygen either due to poor storage condition or the use of poor quality cork. In the case of screw-cap, it may be rare to see this but if there is slippages of wine through the cap, it means either the bottling machine or the glass bottle is not made to specification.

Second, check the level of the cork at the bottle opening. If the cork has been lifted a little, i.e if it is not sitting flat in the bottle opening, it strongly suggest bad storage condition e.g the wine may have been stored in a warm room over an extended period of time. The result could be an oxidized wine and you can pick up the wet cardboard smell upon nosing.

Third, look for the condition of the label on the wine bottle. If the label is crumbled and is not pasted onto the surface properly, it again suggests that the bottle has gone through some temperature swing from warm to cold and vice versa. This alone does not suggest that the wine is spoiled, just that the wine has not been treated with proper care during its shelf life.

Once you are satisfied that the exterior is looking good, we can at least be confident that the wine has been handled properly thus far. The next step is of course to open the bottle and pour a small portion into the appropriate wine glass. The first thing is to study the color and the clarity of the wine. If a wine is too light in color (for a young Red wine) or if it is excessively brown (for a young white wine), it may suggest an inappropriate application of sulfur dioxide. However, the appearance is not conclusive and is only a data point to be considered in subsequent tasting. Clarity is important. If the wine is murky, it is generally not a promising start, especially in white wine. There are some winemakers who opt not to filter their wine (especially Red wine) but the wine should not look murky.

To nose for any spoilage, you will be looking out for odd odors such as rotten eggs or garlic (H2S), bandaid (Brettanomyces), wet cardboard (oxidation), corn chips or metallic bitter finish (high pH wines), moldy or musty (cork taint), nail polish or vinegar (high volatile acidity). Most of these are a result of poor winemaking techniques or barrel storage conditions. However, oxidation may be a result of poor transportation or storage conditions especially when loads of wines are being transported in un-refrigerated container by sea over summer. The heat in the ship storage area over an extended period of time may have the corks expanded and not sit properly in the bottle opening.

As for the palate, a spoiled wine normally gives a SHARP attack to our taste buds or leave behind a trail of very unpleasant finishing. Wines with high volatile acidity will attack our throat like we have just had a mouthful of vinegar. Unusual bitterness is also an indication of spoiled wine, suggesting the presence of spoilage micro-organisms when the wine pH is too high.
In general, a wine is safe-guarded by observing an acceptable range of pH, acidity, alcohol and sulfur dioxide. Unfortunately, during the winemaking process, infections can occur if equipments are not sanitized carefully, storage conditions are not proper. Even if the wine is of good quality upon bottling, transportation and cellaring conditions can also affect the final quality.

Copyright of Wine Treasures Pte Ltd

By Cher Lim
Wine Treasures Pte Ltd

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Wednesday, June 14, 2006

How to tell that this wine is spoiled?

It is pure coincidence that I tasted two spoiled wine in a row within a week. One customer asked me the characteristics of a spoiled wine and how to recover from such unpleasant experience. The short answer is that sometimes it is a good idea to taste some spoiled wine so that we know what it is like. To recover your fresh palate, the best way is to gaggle with a pint of room temperature water and let your palate settle down before going for a new glass of wine.

So, how does wine spoilage come about? There are two possible causes – chemical spoilage and microbial spoilage. Chemical spoilage is mostly contributed by careless treatment of the wine that results in excessive addition of chemicals such as sulfur dioxide. Legal bound of free sulfur dioxide during bottling is not more than 25-35 ppm. Remnants of carbon dioxide during bottling will also cause a “spritz” feeling on the tongue. In most cases, this sensation is not desired and should be eliminated. Sometimes, if the smell of rotten eggs, sewage or garlic is found on the wine, it is most likely due to the untreated hydrogen sulfide which could later be transformed into mercaptans and disulfides.

Microbial spoilage is a result of undesired growth of microorganisms in wine. Factors such as pH, temperature, residual sugar, nutrients, oxygen will affect the growth if they are not controlled within the range. For example, the presence of oxygen during fermentation will encourage the growth of acetobacter, a bacteria that is always present in wine. It starts to propagate by consuming alcohol and produce acetic acid and ethyl acetate. A little acetic acid contributes a small sensation of sharpness to the throat. Too much of it will be very undesirable and considered a spoilage. The ethyl acetate is generally present in late harvest wine, responsible for the unpleasant, pungency smell. Since this bacteria is inherently present in the wine, sulfur dioxide is not able protect the wine against acetobacter. The only way to prevent their growth is to minimize their contact with air (oxygen) and keep the wine cool (e.g below 10C).

Therefore, when we happen to taste a glass of spoiled wine, the unpleasant mouth feel is an indication of its winemaking as well as storage conditions. The color and smell of the wine usually give away information of its quality before it is even consumed. An oxidized wine is brownish in color (if it is a red) and has the unpleasant pungency nose. Its taste is acidic, perhaps reminding you of vinegar, leaving behind a trail of stuffy sensation in the throat. In case we have the honor of drinking such wine, it will be an eye opening experience that adds to our palate memory, inspiring further exploration in the world of wine.

Reference: Dr Yair Margalit (1996), Winery Technology & Operations published by Wine Appreciation Guild.

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By Cher Lim
Wine Treasures Pte Ltd