Dear Friends of Monolithos,
From the earliest days of wine-making, some 8,000 years ago, until the middle of the 19th century, the fermentation process was considered something of a miracle. Wine-makers made wine for several millennia without actually knowing what yeast was or what it did. It was only 150 years ago that Louis Pasteur identified yeasts as the agents of this change. Furthermore, it wasn’t until the 1970s that cultured yeasts were routinely used in wine-making.
Today, a lot is known about yeasts, the way they are being used and the way they can affect a wine. However, where they come from has become a controversial topic within the wine industry. Many wine-makers swear by wild yeast fermentation. On the other hand, many swear at it. This short overview will attempt to provide some basic information to help you to understand the issues involved and the importance of this dispute.
Yeasts, like all microbial bacteria, can be found almost everywhere. They are found in the soil, in the air and on the grapes themselves. In a wine-making environment, they can hide in the barrel or on the grape presses, and there isn’t just one species but rather hundreds!
Once the grapes are crushed, there is a good chance the resulting must already contains a variety of yeasts which go to work on the sugar content of the pulp. Depending on environmental conditions, the quantity and the particular strains of yeasts, fermentation should spontaneously start within 48 hours. Fermentation is a natural process during which the yeast converts the sugar in the grape juice into alcohol and carbon dioxide gas. In addition, the yeast not only converts sugar to ethanol, but also produces esters and other compounds which contribute to the wine’s flavour and aroma. Extraction of flavour and colour from the grape skins (for red wines) also occurs during fermentation. But as the juice begins to turn into wine, the environment changes and the varieties of yeasts that thrived at first will die off, replaced by previously dormant, more alcohol-tolerant strains.
Dead yeast cells will float to the bottom of the fermenting vessel and form what are referred to as the “lees”. However, even dead, these yeast cells continue to impart flavours, and the time that a wine spends on its lees will vary depending on the style of wine the wine-maker wants to make. It is therefore apparent that if the must is left by itself, the yeast residing on the grapes or in the winery will start the process of fermentation on its own.
There are about 150 species of yeast. The most copious is the “kloeckera apiculata”, which is active only up to 5% alcohol level. The most important and relatively rare varieties belong to the “saccharomyces cerevisiae” and “bayanus” species, which are active up to 14% and 18% alcohol levels respectively. Whatever the source, saccharomyces counts will be small at the beginning of fermentation, allowing the other players to work their magic; but sooner or later, whatever saccharomyces happen to be around will take over, multiply and suck up the sugar.
Common practice in the wine industry is to add a sufficiently large dose of a single strain of yeast (saccharomyces cerevisiae) to the grape juice to start the “inoculated” fermentation. Saccharomyces cerevisiae is referred to as the “true” wine yeast because its alcohol tolerance enables it to ferment up to and beyond 13% alcohol. Most wine-makers add some sulphur dioxide (SO2) on crushing to reduce the risk of oxidation and also to kill off rogue microbes. This will slant things in favour of saccharomyces cerevisiae and the more robust of the native species, eliminating some of the less desirable wild yeasts and spoilage bacteria which tend to be more sensitive to the microbicidal actions of SO2. Temperature also affects the balance of yeast species in the fermentation.
Over several years of laboratory research, the more active strains of yeast were identified and selected. By isolating and culturing the dominate yeast strains from a variety of favourable locales, scientists have made it possible for wine-makers to select the yeast most appropriate for their needs. One can choose a yeast which can tolerate high or low temperatures, that produces abundant or little foam, that works very fast or very slow, that changes or preserves natural flavours and characteristics, that imparts certain desirable or non-desirable off-flavours, that lays down compact or loose lees, or that works particularly well in producing particular types of wine.
The fact is that cultured yeasts have only been in the wine-making picture within the last century. For thousands of years previously, all wine was fermented on wild (indigenous) yeast. There’s something of an ideological divide between those wine-makers who advocate natural fermentations and those who choose to use cultured yeasts, although many wine-makers sit somewhere in the middle. Making wine with wild yeast has been a source of debate for many because of its unpredictable nature. Detractors see wild fermentations as a haphazard route likely to yield a spoiled wine; proponents not only claim their wines taste better, but often go on to insist that relying on the indigenous yeasts that are already on the grapes and in the air fosters less manipulation and more expression of terroir.
Let’s make it clear here that all yeast strains associated with wine-making are “natural” yeasts, that is, they are found in nature, but they are subdivided into wild and cultured strains. Wild yeast, also known as native, indigenous, local, ambient, or spontaneous, is the naturally existing yeast in the atmosphere, on vegetation or blowing around in the air. It is present on the grapes as they come into the winery, as well as on winery equipment and in barrels and tanks. The various species of wild yeast floating around a particular vineyard or winery may not be the same as somewhere else. For centuries, wine-makers have been returning the stems, pressed-out skins, seeds and pulp (pomace) of the wine grapes to their vineyards as fertilizer. The pomace is rich in yeast, and that used in making red wines is extremely rich in whatever strain dominated the process of fermentation. By returning the yeast-rich pomace to the vineyard, the wine-maker alters the natural mix of yeasts locally. Over time, the selected strain dominates so firmly that the wine-maker can achieve precisely predictable results by simply encouraging spontaneous fermentation of newly pressed must.
Wild yeasts can be broken down into two sub-categories: wine yeast and spoilage yeast. Consequently, any wild yeast species – whether good or bad for making wine – can end up in the fermentation tank, colonizing and consuming the natural sugar in the must. The wild yeasts found in fermenting wine normally include several species actually present together in the fermenting wine. They each have different reaction rates and will produce some different end products as they ferment the juice sugars to alcohol. With slow, lengthy, wild yeast fermentation, it is more difficult to predict the outcome, positive or negative, because the wine-maker does not know which yeast strains are active in the fermentation process.
One of the most common characteristics of indigenous yeasts – even good ones – is their low resistance to alcohol. Many wild types of yeast are unable to perform once alcohol levels reach 6%. The result is stuck fermentation, flabby wine with a low immune system, and a pile of unwanted residual sugar – to name just a few of the drawbacks. Another risky feature is the fact that wild yeast exists on grapes in much smaller numbers than a dose of inoculated yeast. Therefore, it takes longer for wild yeast to colonize – up to a week in larger batches – leaving the grapes open to infection from other spoilage organisms and from oxidation. In addition, once fermentation begins, it is longer and slower and at a lower temperature. A third risky feature is the unpredictable by-product of off-aromas and esters that wild yeast can impart to the wine.
Now, laboratory selected “saccharomyces” yeast gains an advantage and grows from less than 1,000 cells per ml to between 1,000,000 and 2,000,000 cells per ml within 24 hours, thereby dominating the fermentation. This is extremely important for larger production, less expensive wines, where a yeast strain is chosen to get the job done as expediently as possible, converting all of the sugar to ethanol and freeing up the tank for the next load of crushed grapes.
For smaller production, fine wine, varying the yeast strain as well as the temperature and duration (maceration) of fermentation can enhance the wine’s aromatic and flavour characteristics. Given the right grape, yeast and instructions, anyone can make almost any type of wine. In wine-making, yeast and sulphur are related issues. The guaranteed way to make a “clean” wine is to use high levels of sulphur to eliminate microbial activity in the grapes and to inoculate with a commercial yeast strain with high sulphur tolerance. This offers a fast, reliable and predictable fermentation. Cultured yeast strains are specifically selected varieties that have been isolated for their various desirable characteristics. Some of these characteristics are: attractive aromas, fine texture in the mouth, reliability in avoiding stuck fermentations, no excess of foam in the barrels, the ability to ferment under conditions that would normally be difficult (such as with grape juice containing high levels of acid or sugar) and their ability to ferment at cold temperatures to maintain fruit flavours. Overall, they offer great advantages in reliability, predictability and fault-avoidance.
The proponents of cultured yeast emphasize these significant advantages for any wine-maker, and believe that those who do not recognize and exploit them are limiting their experience and potentials. The secret of good wine-making is good ingredients and absolute control over all conditions. Also, there have been many questions raised regarding the use of natural yeasts such as the efficiency of sugar-to-alcohol conversions, off-aromas, stuck fermentations, foaminess, volatile acidity, filtration, lack of fruitiness, and ageing potential.
Those who take the more “natural” path believe the indigenous yeasts that are on the grapes and in the air at a particular place are as much a part of the terroir of the wine as the grapes themselves. The idea of replacing them with cultured yeasts is seen as not only removing a wine from its “place”, but as artificially flavouring a wine. Wine is considered as an agricultural product dependent on the climate, soil and in general the terroir which differentiates wine from manufactured drinks such as whisky, beer or gin.
Paradoxically, the most attractive attribute of wild yeasts actually results from their unpredictability, because they can often create additional levels of flavour and aroma complexity in the finished wine. They may also create softer wines because wild yeasts are not as efficient at converting sugar to alcohol as cultured yeasts, so even when the wine is fermented to dryness, it has less alcohol and often subliminal levels of residual sugar. In a “model” wild fermentation, the non-standard strains dominate the action, one after another, over the course of several days, perhaps for half the total fermentation time. The result of a sequential fermentation is a wine with complex flavours, fruit and aromas, with good alcohol. Many wine-makers believe that there are qualities that wild yeast imparts to wine that cannot be achieved with cultured yeast. Wine-makers who rely on wild yeasts usually swear by them and praise their virtues. Wild yeasts have been used for many years in some Old World European wineries, which have been blessed with desirable strains of yeast in their vineyards, strains that seem to be relatively consistent over time.
In recent years, many New World wineries are catching on and beginning to practise spontaneous fermentation with favourable results. Wild yeast is one in a number of ways to develop complexity in wines, even if this added complexity is short-lived. This quality factor coupled with the fact that the majority of wine-makers feel these methods make their craft more interesting and challenging, guarantees that the use of wild yeast will continue to grow in importance and popularity in the production of super premium wines. Others do it for quality reasons: native yeasts are thought to produce wines with a fuller, rounder palate structure, and the ferments tend to be slower and cooler, burning off fewer aromatics. Wines made with wild ferments are often richer-textured and have more complexity. There is also a cost saving: cultured yeast has to be paid for.
It has been estimated that in an uninoculated ferment, as many as 20 to 30 strains participate. But as alcohol levels reach 4%–6%, the native species can’t cope with the hostile conditions, and the alcohol-tolerant S. cerevisiae will take things onwards from here. So the key difference between natural ferments and those carried out by cultured yeast inoculations is in the early stages of fermentation.
Aside from the properties of the wild yeasts themselves, spontaneous ferments cause a delay in the onset of vigorous fermentation. In red wines this will allow oxygen to react with anthocyanins and other phenolics present in the must, enhancing colour stability and accelerating phenolic polymerisation. This enhanced exposure to oxygen before vigorous fermentation is underway could have important flavour and textural effects on the wine thus produced, quite separately from the characteristics contributed by the diverse set of wild yeasts carrying out the fermentation
As different clones of a particular grape variety are planted in different countries or locations, they produce slightly different wine. Equally, wines differ among others according to the strain of yeast used, the temperature at which they are vinified and the length of time they are kept in the barrels. A wine-maker does not get enough chance to experiment with all these factors. A chef cooks at least one meal a day and a brewer produces beer continuously, but a wine-maker makes a vintage wine only once a year. This may help to explain why experiments are slow in producing reliable results.
There are groups of wine-makers who continually look for techniques that will help them improve wine quality. The “indigenous yeast” trend became a buzz word popularized by influential wine critics of wines made with more natural, less interventionist techniques.
Experienced wine-makers allow spontaneous fermentation to begin while watching the must carefully, taking regular readings of the amount of sugar or specific gravity of the must, to determine the current alcohol. After they estimate that the alcohol has reached 3% or 4%, they may sometimes choose to inoculate with S. cerevisiae to ensure complete fermentation. They get the best of both worlds: complexity of wild yeast, and sound full-bodied wine. While no one can predict results with spontaneous fermentation, there are certain features you can watch for to help you determine if you want to take that walk on the wild side. Although it is not possible to know what types of yeast are on your grapes, or in your must, sometimes the very condition of the grapes or must itself will help you predict the odds.
Many things are overheard at a wine tasting as a wine is analyzed and dissected. It may smell like anything from roses to grapefruit, rubber to vanilla. It might taste of plum or cassis, or have that mineral quality that reminds you of when you were a kid and chewed on your pencil in class. There might be people qualifying the wine’s texture – dry, rich or acidic.
As stated earlier, it is during this fermentation process where the majority of the flavours, aromas and textures of a wine are created. And as each yeast species has its own tolerance to alcohol and temperature, each will metabolize the sugars in the juice in different ways. Some will create esters, compounds responsible for the aromas of a wine. Others might lower the acidity the same juice. This means the same juice fermented with different yeasts will yield different results. As this process is better understood, so is the wine-maker’s ability to control the smells, flavours and textures of his or her wine.
This debate tends to follow the New World-versus-Old World division, with the Old World wine-makers relying more on indigenous yeasts. New World wine-makers in countries like Australia , New Zealand and California are more likely to accept new technologies. Certain wineries, mostly in the New World , are looking at finding yeast cocktails that will enhance aromatics and reduce acidity. One need just look at the success of the New Zealand sauvignon blanc. Its unique aromatic profile, highlighting the more exotic attributes of the grape, is largely a result of a cocktail of cultured yeasts, and it has created a unique and easily identifiable style.
So once again, it is a question of how we use the technologies that are available and what is important for each individual in a wine. There is little doubt that using cultured yeasts will allow for a more consistent wine from year to year. Fermenting with wild yeast can be risky business, but for many daring wine-makers, it’s a risk worth taking. Compensating for the higher risks means paying more attention, monitoring every batch closely and putting more time per gallon into the wine.
But there is a definite movement towards cultured yeasts. The ability to control what a wine will taste like, especially for more mass-produced wines, has obvious benefits. Commercial yeast remains the norm, particularly for larger-scale producers, while the wild bunch tends to be on the artisan side. The philosophical overlay--less processing, more terroir--is sometimes there, but the driving force is a perception of wine quality.
Wine News and Information
The Prince of Wales has reduced his motoring emissions by running his 38-year-old Aston Martin, a 21st birthday present from the Queen, on fuel made entirely from wine.
Sir Michael Peat, the Prince’s private secretary, said: “The bio ethanol from our supplier happens to be made from wine.” But the wine is not left over from banquets at Clarence House or dinner parties at Highgrove, the Prince’s Gloucestershire residence. The EU sets strict limits on wine production and any excess is not allowed to be sold on the market. One way it is redistributed is for use through environmental fuel.
Prince Charles now drives the Aston Martin Volante convertible car only in the summer and clocks up around 300 miles each year. The Prince’s Jaguars, Audi and Range Rovers have all been converted to run on 100% bio diesel made from used cooking oil.
The annual report of the Prince of Wales and Duchess of Cornwall said: “When their Royal Highnesses are travelling in the UK , the aim is to reduce emissions through greater use of cars, trains, and turbo-prop aircraft. In accepting and arranging engagements, more consideration is being given to reducing travel distances.”
Last year, France ’s wine and spirit industry exported nearly $15 billion (€9.4 billion) worth abroad, a record and an increase of nearly 7% year-on-year, according to the French Federation of Wine and Spirits Exporters. But the good overall export performance masks a broader crisis. While Champagne and fine Bordeaux find overseas markets, lower-quality wines and lesser-known wine regions have struggled against competitors from New World countries such as Australia and Chile . Chronic over-production has also hurt, forcing European producers who can’t sell their wine at decent prices to distil billions of bottles of perfectly drinkable wine into pure alcohol for use in disinfectants, cleaning products or gasoline additives. The European Union agreed in December on a massive overhaul of the industry, including tearing up swaths of vineyards, doing away with overly intricate labelling and reaching out to consumers around the world instead of relying on age-old reputations.
Wine is often served at the wrong temperature. Too cold, and a wine’s complexity and aromas are numbed; too hot, and it tastes alcoholic and flabby. The old advice about serving reds at “room temperature” comes from the days when the “room” in question was a cool medieval castle, not in today’s centrally heated homes. Red wine should be served at about 60ºF, though some light reds are better served cooler. White wine should be chilled to about 55ºF; the glass should feel cool but not ice-cold.
Wine sales growth in the UK is grinding to a halt as the economic downturn hits consumers’ disposable income, says the Sunday Telegraph. It quotes Nielsen figures showing wine sales for the four weeks to 17 May down by 5%, or about 4.5 million bottles, against the same period last year. This contrasts with a 6% growth in the year to the end of February 2008. The Wine and Spirit Trade Association blamed Budget tax rises for the decline, as well as the economic climate.
Monolithos Monthly News
The very warm days that we’ve enjoyed this summer have resulted in very healthy, stimulated vines. Vines love heat! During the summer period, the grapes get their maximum amount of sun, which is the base for the photosynthetic process. The result is the maximum amount of grape sugar, and by proper management, a perfect balance between sugar and acidity is possible to achieve. The end product will be strong wines with high alcohol content and good body and often with lots of tannin that is crucial for storage.
We’re likely to be harvesting in late August/early September. This is particularly good for our reds.
Five years ago, we planted Shiraz vines in our site at “Ayiasmata”. This year we hope to enrich our Ayios Stephanos Red, a blend of Cabernet, Mavro and Shiraz , entirely from our own vineyard. They say patience is a virtue!
Last July, we bottled the remaining Monolithos white and we are ready to satisfy the growing demand for this crispy and pleasant summer wine. The winery is opened to visitors most weekends. 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.
We thank you for your continued support, take care and remember:
“Holidays are about celebrations and social gatherings, so is wine. Wine is made for entertaining, enhancing and enjoyment.”
Regards from all of us here at Monolithos
No comments:
Post a Comment