Cork stoppers became the industry standard for wine bottle seals, probably going as far back as the 1600’s. Manufacturers of alternative wine bottle seals have made several attempts to wrest the market away from cork manufacturers, particularly over the last 30 years. In spite of these efforts, cork remains the dominant wine bottle seal, with a market share of around 90%.
For centuries, natural cork is unmatched as a wine closure. Among its many important and properties are its lightness, ability to offer blockage to liquids, resistance to wear, temperature endurance and its well-known compressibility.
The secret to cork’s performance is its unique, honeycomb cell structure which technology cannot replicate. Each cell is sealed, filled with air and not connected to any other cell. Because the cells are all full of air, corks are lightweight.
The cushion-like cork cells also display what is known as elastic memory. Cork can be compressed and, when released, will return to its original volume. As the cork is compressed, the air in the cells is compressed. When pressure is removed, the cork expands back to its original volume.
Due to its cell structure, cork is waterproof. Individual cells are sealed so that they’re not connected to each other. No capillary action or wicking can happen in cork.
Being elastic, cork is also more tolerant than other materials of changes to temperature and pressure. Cork resists moisture and can age for long periods without deteriorating. It is naturally fire resistant, but that doesn’t mean it’s fireproof as it will burn if heated long enough. In addition to these characteristics, cork’s lightness and chemical inertness make it ideally suited as a wine closure.
Finally, cork has a high friction surface i.e. it stays in the bottle. As the cork is cut, millions of cells are ruptured. This forms rough domes that can seal onto a smooth surface such as a glass bottleneck. When compressed they constantly try to return to their original size, thus maintaining a tight seal. This means the cork exerts a very even pressure against the surface of the bottle neck and can compensate for imperfections in the bottle.
Recent research by the University of Bordeaux has confirmed that natural cork allows a tiny amount of oxygen to permeate into the wine bottle after it has been sealed. This tiny amount of oxygen has an important and beneficial impact on the development of the wine in the bottle.
For many people, a glass of fine wine is the perfect treat after a long day at work. However, for those whose work is wine, it is more than simply a way to relax. It takes years, even decades, to perfect the winemaking process. Wine makers concentrate on flavours, acids, grapes, fining, filtering, corking bottling and much more. And wine makers run into problems in all of these areas along the way. Fortunately, it’s easy to recognize and fix most wine problems by learning a little information about their causes.
One area which often causes considerable concern in the winemaking field is the use and problems associated with the corks. To start with, there are several types of corks on the market which can be very confusing for the wine maker. Type selection is dependent on the style of wine being sealed and the expectant length of time before the wine is consumed. Other factors determining wine cork type selection and treatments include bottling speed, still or sparking wines, sweet or dry wines, red or white wines, bottle type and size. The winemaker must decide what he or she wants the cork to do. If the intention is to drink the wine soon after bottling and the quality of the cork is not an issue, then the economical agglomerate cork will fit the bill. If presentation and longevity of the wine are more important, then a high quality natural cork is more appropriate.
With all the beneficial properties of corks as bottle closures, one significant defect is a constant threat. This is “corkiness,” a condition that exists when wine is tainted by the presence of a chemical compound called 2, 4, 6-Trichloroanisole (TCA). This compound appears to be caused in the cork by the interaction of moisture, chlorine and mould. Corks are often exposed to these elements during their production and this is the time TCA is likely to be formed. (TCA also occurs naturally in the wood and bark of many trees, including the oak family.) The human nose can detect this “corkiness” at concentrations as low as four parts per trillion! Unfortunately there’s not much the winemaker can do to control TCA. It’s virtually impossible to detect a mouldy cork before it is put into the bottle.
A wine that is slightly corky may respond to a bit of aeration. If you encounter a corky wine, swirl some in a glass and see if the corky smell disappears. If it does, you can drink the wine after decanting it and allowing it to breathe for 15 minutes.
However, a “corky” wine and a “corked” wine are not the same thing. A corked wine is one that has been affected by contaminants that were on the cork at bottling time (TCA). A severely corked bottle is easy to detect. It will smell like a damp carpet or a flooded cellar. It gives that musty unpleasant odour. And this is fine because you can detect straight away that something is wrong with the bottle. In the last decade, the cork industry responded to the TCA problem by spending millions on research to find the cause and its cure. A chlorine-free cork treatment process was developed and this has helped greatly. Industry sources acknowledge that 1%-3% of all bottles suffer from some cork-related problem.
Another common problem caused by the cork is oxidation. Wine oxidation problems occur if the cork shrinks due to storing conditions. As the cork becomes smaller, air enters the bottle and oxidizes the wine.
Furthermore, a defective cork can cause problems such as leaking. Sometimes in a warehouse or during transit in the summer months, a substantial increase in temperature (30°C to 35°C) can occur. The rise in temperature can result in excess head pressure and push the cork up, thus resulting in wine leakage. It should be pointed out that two factors contribute to high pressure with the increase in temperature: First, the expansion in the volume of the wine and second, the expansion of gas in the headspace (the air space in the bottle between the wine and the cork). The problem is made worse since gas expands 10 times more than the wine with the rise in temperature. Lack of humidity can also cause some leakage.
Some bottles can leak even without bad temperature management. One reason could be that some producers fill their bottles too much, resulting in a slight leakage at the time of bottling. However, the existence of signs of leakage does not necessarily imply that the wine in the bottle is spoiled. In most cases, it is perfectly sound.
Whenever one comes across a leaky wine bottle, the immediate reaction, in most cases, is to blame the faulty cork, and this may sometimes be justified. However, it needs to be emphasized that there are many factors other than a defective cork that can contribute to the problem of leaky bottles. Some of these include: bottle, filling head, corking machine, the operator of the corker, and storage and shipping conditions. However, be wary of bottles with obvious and particularly excessive signs of leakage.
True leakage (bottles that leak continuously when inverted) is very rare in bottled wines. So-called “leakage” usually involves the expulsion of a few drops of liquid, maybe just the once or maybe on several occasions, until the internal pressure drops below the sealing pressure of the cork. In addition to lowering the internal pressure, the expulsion of liquid enlarges the headspace volume, and this reduces the incidence and magnitude of further losses with any increases in temperature. Because not all bottles leak and because the incidence of leakage can vary from one bottling session to another, there is a widespread misconception that the differences in performance must be caused by differences in the sealing ability of the individual corks. In fact, the major variable is bottle-to-bottle variations in the headspace pressures. This can be observed during the course of bottling, and also in retail bottles taken from the same carton. The reason for this variation is the different amounts of air that are often incorporated in the bottles before sealing.
From the practical point of view, it is a matter of balancing all the risks and costs when choosing the type of corking machine, operating techniques, the dimensions, density and moisture content of the corks and the level of control of the overall operations. Sealing wine bottles is an integral part of winemaking, and winemakers cannot distance themselves from the responsibility of ensuring that it is carried out correctly.
There are three different types of corkers available. All of them work primarily in the same way. They have a compressing iris that evenly compresses the cork from all sides, down to about the diameter of a dime. Then they drive the cork into the bottle. The main difference between them is speed. Bench and floor model corkers are mainly used in most wineries.
After wine bottles have been corked they need to be left standing upright for at least one or better still two days. This is to give the corks time to re-expand into the neck of the bottle and create a complete seal.
After the re-expanding period, the bottles will need to be stored on their sides so that the wine is touching the cork. This is to keep the cork moist and expanded. If the bottles are stored upright, the corks will eventually dry out and the wine bottles’ seal will be compromised. Over time, this could lead to problems with oxidation and possibly spoilage of the wine.
Wineries can use various criteria for assessing cork quality. The dimensions of the cork should be appropriate for the size of bottle and the inside surface of the neck should be smooth with a proper taper. The dimension of the neck should be checked with a gauge. Most wine bottles are produced according to certain standards, with a bore (inner neck) diameter of 18.5 + .5 mm at the lip (mouth) and 21 mm, 4.5 cm below the mouth. In other words, the width (diameter) of the bore increases from 18 mm to 21 mm over the length of 4.5 cm from the mouth. Note that the sides of the bore are not parallel. This design helps in limiting the movement of the cork after it is inserted. The diameter of the cork affects the sealing force exerted by the cork against the glass surface. It is, therefore, critical that the cork diameter be very close to the specifications.
The corking machine should be cleaned and maintained according to the manufacturer’s directions, with the corking jaws cleaned and checked for wear and tear. The plunger should be adjusted so that the cork is inserted to the proper depth. It should not be pushed more than 1 mm below the top surface of the bottle mouth. To ensure cork insertion to the proper depth, the moisture content of the cork should be uniform.
Insertion of the cork into the bottle compresses the air trapped below the cork and above the wine, and generates excess pressure in the headspace. If the bottle is laid on its side or upside down shortly after corking, the pressure in the headspace can force some wine out, thus causing a leak. Hence the necessary to release excess pressure and minimize the risk of wine leakage, the bottle should be stored upright (off the cork) for several hours immediately after corking.
Wine should preferably be bottled at a temperature of 15°C to 20°C. If the bottles are filled with cold wine, the fill level should be adjusted to allow for the expansion of wine volume with the rise in temperature. It is also important to keep the bottles upright until the wine reaches the expected storage temperature. The bottled wine should be stored in a cool dry place at a temperature of between 14°C to 18°C.
Quite often, the sizes of opening these bottles have do not work well with the size of corks that are available. In addition, the shoulder of these bottles will often start too early, resulting in not enough neck for the cork. The bottom of a compressed cork will likely flare out while still in the bottle. When this happens, the cork is often drawn down on into the bottle by this flaring action.
To get a good cork seal on a bottle, you will want to use a “straight” cork as opposed to a “tapered” cork. A straight cork is cylinder-shaped and provides the maximum amount of sealing surface possible. The sealing surface of the straight cork is the whole length of the cork, whereas the tapered cork seals only at one point along its side – where the cork meets the glass.
One simple way to seal a wine bottle with a straight type cork is to use “mushroom corks”. These are straight corks that have a plastic top on them for gripping. They can be pushed in by hand and fit fairly tight when using a standard cork-finished wine bottle. Mushroom corks will work fine for wines that are going to be consumed within 12 to 18 months.
To conclude, modern winemaking has done much to keep the majority of wines sold today consistent and free of faults, even if the wine isn’t to everybody’s taste. But faulty bottles still come along, particularly corky or corked wine. Sometimes the bottle is obviously not right, and it’s just a matter of returning it to the waiter or shop where you bought it. If you spot a wine that resembles one described above, however, do speak up. The chances are the staff know less about wine that you do, and it’s likely that you’ll be offered a replacement, even if it comes with the almost obligatory “It tastes alright to me” from the manager.
Wine News and Information
During the years 2008 and 2009, the economic crisis and the subsequent deceleration in consumption, which added to the already existing problem of over production, adversely affected the global wine industry. The sharp decline was primarily attributed to a drastic reduction in consumption in the European Union, the largest market for wines worldwide. However, in 2010 wine, the niche category in the alcoholic beverages market realised a healthy recovery with a steady growth forecast over the next few years. Recent research findings confirm the fact that moderate consumption of wine prevents heart disease, cancer, Alzheimer’s disease as well as muscular degeneration. The underlying health benefits of wine would also enable the associated industry to promote it as a household as well as a restaurant product. Developing countries like Russia, China, Australia and India, to name a few, are expected to drive future growth in the market. Changing lifestyles in these countries is proving to be a major win for the growth in wine consumption. Previously, interest in wines was confined to middle-aged customers, however today, a growing base of younger consumers are exhibiting a marked preference for wine over other alcoholic beverages.
Over the last few years, pressure on winemakers to produce wine at low prices for supermarkets in Australia meant growers were being paid less than the cost of production. In 2010, some retailers were selling wine for as little as $5 a bottle, while “cleanskins”, a generic labelled bottle that doesn’t identify the winery or winemaker, could be found for as little as $2. These prices are certainly unsustainable according to the Australian Wine Grape Growers Association. The party may be over for the wine-loving consumers addicted to low prices for their favourite tipple. “The industry is going broke,” Australian Wine Grape Growers Association executive director Lawrie Stanford said. Furthermore, production is on the decline and according to the Australian Bureau of Statistics, the total grape crush for 2009-10 was 1.6 million tonnes, down 7.5 per cent on the previous year. Also this year’s spread of disease, such as downy and powdery mildew will reduce the 2011 crop further, easing the surplus of the past few years.
According to data released last year by the St. Helena, California-based Wine Market Council, a trade group, “millennials” are pursuing wine for a variety of reasons. They equate it with sophistication as it allows them a means to connect with friends, and they see it as a more healthful alternative to other alcoholic beverages. “It isn’t just cheap wine that has gotten their attention,” said the group’s president John Gillespie, noting that millennials tend to purchase more imported wines than baby boomers. He added that it’s important for wine producers not to dumb down their message when marketing to younger consumers, noting that the Internet generation is thirsty for information and more sceptical of advertising. “When we’re out and about in a wine store and we see a label we’re interested in, we have the ability to research that right away and make our own decision,” said Rick Breslin, co-founder of the California-based startup, which began in early 2009 and now delivers nearly a million wine recommendations every month. “It’s going to give you information from the producer, from several publications and other consumers.” Some entrepreneurs credit millennials with redefining how consumers of all ages experience wine.
Monolithos Monthly News
The good weather of February and March allows for outdoor work once again. By the end of February, the grapevines are pruned to help control the yield and quality of the coming year’s grape harvest. If not pruned back, the number of buds that would bloom and turn into fruit would be of a lower quality. Any wood cuttings left over from pruning are removed or burned in the vineyard. March is the time to plough and aerate the soil. By the middle of March, the grapevines begin to come out of their dormant stage as the sap in the roots begins to flow.
Having submitted the new winery plans to the Town Planning Department, we are now waiting patiently for their approval. In the meantime, we are looking into the details regarding other issues such as project management, building contractors, structural engineering aspects, equipment suppliers, mechanical and electrical design considerations, heating, cooling, refrigeration, water and electricity supplies, solid waste disposal, waste water treatment and irrigation, health, safety and the environment, access road and parking requirements, etc.
Currently, all the 2009 wines are available for tasting and purchasing. If at any time you are passing near the village of Pachna and wish to visit the winery or purchase any of our products, Martin Wood will be pleased to meet and assist you at his “Fig Tree Villa” in Pachna, so do not hesitate to phone him at 25-816212 or 99-165995.
Just about every wine lover has an occasional dream to start his or her own winery. They could make exactly the wines they enjoy, spend all day wandering through the vineyards, sit on the back terrace and taste the fruits of their own labour. Is this your dream? If so, then first reflect on this old saying from experienced winemakers:
“The best way to make a small fortune in the wine business is to start with a large one.”
