Wine is regarded as one of the most popular, and diverse, alcoholic beverages in the world. Whether it be a crisp white wine, or a robust red, wine requires proper conditions to protect it from spoilage. Wine is perishable, and when exposed to the enemies of wine, its complex blend of flavours and aromas can be severely compromised. Most of us have heard that wine ages in the bottle, but does wine go bad? Unfortunately, wine does go bad.
So, how does wine spoilage come about?
Wine can be spoiled in many ways – from the vines to fermentation to aging and even after bottling if the bottle is stored improperly. There are various types of wine spoilage, some include microbial spoilage, exposure to oxygen, pH levels and high acid content. Defects that take place during wine processing at the winery are due to two possible causes, namely chemical and microbial spoilage. Defects can also occur after the wine is bottled transported, purchased and stored.
During vinification practices, wineries can test spoilage at many different stages, and it is especially important to control fermentation and the sanitation of equipment to avoid spoilage. Chemical spoilage is mostly caused by careless treatment of the wine that results in excessive addition of chemicals such as sulphur dioxide. In order of importance, chemical instabilities can be caused by: Potassium bitartrate, proteins, and phenolics, and to a lesser extend copper and iron. Typically potassium-bitartrate, can form small, clear glass-like crystals. These, whilst harmless, may offend the consumer. In fact, newly-fermented wine is normally saturated with potassium bitartrate. Therefore it is important that wine is cooled to the minimum temperature to which it is ultimately likely to be subjected to prior to bottling so that these crystals do not form in the bottle. Furthermore, wine can often contain unstable proteins that will cause a haze to develop if the wine is subjected to cold or hot temperatures, or over time. Proteins are removed before bottling. Only white wines suffer from protein instability as the phenolics in red wine precipitate out any proteins early on in the winemaking process. The most common treatment for wines with unstable proteins uses bentonite: a refined clay discussed in the previous session on fining agents.
Bacteria are essential to life on our planet and are critical in winemaking for that perfect glass of wine. Not all bacteria are friendly. Bacterial foes can spoil wine in many ways and therefore must be kept in check. The faults caused include bitterness and off-flavours (mousiness, ester taint, phenolic, vinegary, buttery, geranium tone), and cosmetic problems such as turbidity, viscosity, sediment and film formation. Exposure of the wine to heat and sunlight may encourage problem associated unwanted sediments and wine instability. When a wine is stored in contact with air over a long period, spoilage due to the growth of aerobic microorganisms can occur. Aerobic wine spoilage causing organisms include certain yeasts and acetic acid bacteria. Despite the best practice of modern winemaking methods, microbial contamination often occurs during wine production. Spoilage microbes are capable of survival and growth in the wine, potentially producing off-flavours, off aromas, and turbidity. Microbiological contamination is often undetected until related problems in the wine become noticeable by sensory evaluation. Wines are normally checked before bottling to see if the wine is susceptible to these problems.
Proper corking techniques should also be considered during the bottling process to reduce the chance of cork taint which exposes the wine to bacteria that can have detrimental effects on the wine. Once wine is bottled, it can be spoiled if exposed to high temperatures, oxygen or contaminants in the cork. Wine is a complex beverage. It continues to develop flavours and aromas long after you bring it home to enjoy. To keep the wine fresh at home, the most important factor is oxygen elimination. The most common cause of wine oxidation is a poor or broken seal on the closure used. Oxidative changes are an important part of wine maturation. These changes include the development of a golden brown tint during aging, loss of varietal character, and the development of aldehydes’ aroma. These reactions are common to both white and red wine, but they are more noticeable in white wine. Oxygen is the most common enemy of wine. When air gets into a bottle of wine, the wine begins to oxidize. Beautiful white wines will begin to brown, precious reds will fade, and all will take on sharp Sherry-like nose.
The amount of oxygen in wine has an important influence on oxidation. Prolonged contact with air is detrimental to wine quality. Certain wines, such as sherry and Madeira, are exposed to air during the course of their production. On the other hand, premium table wines are produced with minimum or limited air exposure. White wines tend to improve when processed under low oxygen conditions. Red wines usually benefit with air exposure up to a certain point, but beyond this critical point, aeration is detrimental.
Once the wine is out of the hands of the winemaker, the conditions under which it is stored become critical by many different ways. In its broadest sense proper storage means keep it cool, keep it dark, keep it still and if it's got a natural cork, keep it sideways. To store the wine for a long period its temperature should be maintained properly. The science of successful wine ageing is relatively poorly understood, but what we do know is that we like the way that fine wine develops in cellars that maintain a constant year-round temperature of around 10-13ºC, and which are dark and vibration free, with have high humidity. Yet when you start deviating from storage requirements for you'll find that slightly different temperature and duration specifications can add up to a significant difference in a wine's performance, post-storage.
Temperature swings can be detrimental to fine wines, as exposure to heat can cause wine to push the cork out of the bottle, while extreme cold paralyzes wine and ruins its natural development and taste. A cold, dry environment can dry out corks, allowing wine to seep out and destroying the flavour of the entire bottle. Heat can ruin the flavour of a bottle of wine if it is exposed to it for long periods of time. The cool temperatures slow the aging process and allow the wine to acquire beneficial characteristics over time. Temperature affects various reactions involved in wine maturation. Since many reactions are physiochemical in nature, they are accelerated at elevated temperatures. To prevent rapid aging and loss of quality, fresh, fruity and young white wines should be stored at a cooler (<10ºC) cellar temperature.
Wine can become “cooked” by being stored at too high a temperature, and it doesn’t take long for the damage to occur. Forgetting about wine left in the trunk of a car on a hot summer day can be disastrous. Wine can also suffer from being held at too low a temperature. A bottle put into the freezer to chill quickly and left in a bit too long can turn from delicious to flat and lacking flavour, as can a bottle left in a refrigerator for a few months. Heat exposed wines can leak and change in colour.
In general, wines storage areas that fluctuate in temperature by even 10 degrees daily can damage your wines. While the option for storing your wines depends on your budget and available space, by keeping the wine storage basics of cool, dark, still and sideways in mind, you'll find your wines presentable when it comes time to serve them
Light exposure has been known to affect wine aging. Particularly, wine exposure in the ultraviolet radiation range can initiate an oxidative reaction. Ultraviolet light from any source, whether sunlight or fluorescent light, can age wine prematurely. It’s best to avoid exposure to any constant light source when storing your wine. Glass offers wine some protection from ultraviolet light that can affect wine quality. The correct choice of glass colour and modifications to glass composition or glass coatings can further enhance the protection of the wine.
Dark places are best, with little or no exposure to heat or sunlight. Bottles exposed to sunlight can have an off taste, and keep in mind that wines with clear glass are especially sensitive. So, dark place is only suitable for wine storage. The environment that is free from smells and debris is essential for storing wine. Wine that is exposed to ultraviolet light can cause the wine become cloudy, give off strong odours and off-flavours – quickly ruining your favourite bottle of wine. Exposure to sunlight can adversely affect the contents of the bottle and fade the label.
Tannins in the wine are oxidized causing damage to the wine when UV rays reach them. Even dark coloured bottles do not offer much shield from the UV rays. Interestingly, amber-coloured bottles would almost entirely eliminate this problem, but wine producers still favour black bottles – this simply comes down to the marketability of green / black glass as compared with amber, which is perhaps associated with beers and old fashioned medicine bottles.
LED lighting contributes to both the beauty and functionality of a wine storage or display. It use 80% less power, produce no UV radiation, generate almost no heat and offer a 50,000-hour lifetime that virtually eliminates the need for replacing the lights.
If you think it’s OK to store your bottle of wine in the refrigerator for a long time, think again. Not only will you expose the wine to odours, but the vibrations from the compressor can harm the wine, too. When storing wine for aging, strive for a vibration-free environment. Vibration damages the chemical structure and also harms wine by disturbing sentiment, or the wine solids that have settled on the bottom of the bottle.
In general avoid storing wine close to loud household devices such as the washer, dryer, boiler or even rooms that receive frequent foot traffic. Wine experts suggest a vibration-free environment for fine wine because it allows the wine to slowly fully mature. The production of solids and sediment is a natural part of the wine aging process. Vibration of the wine may upset the liquid-to-solid balance and artificially accelerate the production of solids. Vibration can also adversely affect the seal on old, fragile corks.
Remember, wine breathes — so don’t store it with anything that has a strong smell. Odours can permeate the cork and taint the wine and can impact wines that are sealed with corks, which are naturally porous. Store your wine away from garlic, onions, cleaning products, open foods, garbage cans and anything else that may give off a strong scent. Wines get contaminated when unrelated smells enter through the cork. For the wines to mature, choose a proper wine storage area which provides a clean environment.
Another important environmental factor is humidity which keeps the cork sufficiently hydrated, and protects it from oxygen. A humidity level of 50 to 80 percent is ideal for most wines, which is one reason not to store wine for a long time in a refrigerator. Refrigerators are designed to alleviate humidity, so long-term storage could expose your wine not only to oxygen, but to the aroma of last night’s fish or chicken dish. Low humidity causes corks to become brittle and dry, while humidity levels above 80% can result in mould, ruining labels. To keep wine in contact with the cork at all times it should be place horizontally in the storage unit. When placed vertically, they develop deposits of sediment on the bottom.
Most wines are meant to be drunk young. It is no exaggeration to say that over 99% of wine does not benefit from being aged for a substantial amount of time. Even the best white wines should almost all be consumed after two to three years. Quality reds should be given up to ten years to mature (and they may be essentially undrinkable for their first two years).
However, some people prefer a young wine, while others may prefer an aged wine. Wine aging refers to a group of reactions that tend to improve the taste and flavour of a wine over time. The term wine 'maturation' refers to changes in wine after fermentation and before bottling. The term “aging” should be reserved to describe changes in wine composition after bottling. After bottling, once the oxygen picked up at bottling is consumed, the wine is in the absence of oxygen. This is called the reductive atmosphere. Many reactions occur during this phase to contribute to the final bottle bouquet. Some wines require only a short period to develop and generally do not benefit from prolonged maturation and aging. Fresh, fruity whites, picnic style blush, light reds, and nouveau style red wines are produced for early consumption and their quality peaks out in a relatively short time. These wines are generally released within a year of their production. Aging them longer is neither beneficial nor economical.
This brief overview pointed out the most common wine problems encountered at the winery and during storage before consumption. We hope we helped to clarify (and not further confuse) some of the issues surrounding the development of wine faults. You will always encounter some wines with problems you cannot identify.
There are plenty of wines that are good now. As you drink these wines, you'll get an idea of what types of wine you like. With a little learning, you'll get an idea of the style of wine you want to put away. Whether it's a red or white wine, you'll want to store don't forget, how you store the wine will affect how long it lasts as well. Even the size of the bottle will change its life. Getting good advice about particular wine is always a good idea.