Monolithos Wine Dimensions: October 2017
Winemaking, or vinification, is the process of wine production, from the selection of grapes to the bottling of finished wine. The grapes must be healthy and without defects, and the winemaking must be conducted as soon as possible after harvesting with, if possible, whole grapes. If grapes are broken during harvest and/or transport to the winery, defects or problems can arise due to the activity of acetic and/or lactic bacteria which may spoil the final produce.
The first step in winemaking is removing the grape berries from the stem and then compressing them. Today, there are automatic destemmers/crushers which break the grapes apart as the grape berries are separated from the stems. The berries are then crushed by rollers and transferred to the fermentation tank. The advantage of this sequence is that since the stems are not in contact with the must, then extraction of undesirable stem components does not occur.
Grape juice is turned into alcohol by the process of “fermentation”. Historically, winemakers have used spontaneous fermentation, allowing the yeasts and bacteria living on and in the grapes to do the work. However, as the phrase implies, spontaneous fermentation is an uncontrollable process: whole ecosystems of microorganisms live on the grapes and help to produce complex and interesting wines, but can also spoil the process.
When the must has been prepared, selected yeasts, sulphur dioxide and nutrient substances are added. Yeasts are supplied in freeze-dried form and many different strains are commercially available. Sulphur dioxide is generally used in winemaking and has two functions. The first is to inhibit or kill the bacteria and yeasts in the juice and thus facilitate the activity of the selected yeasts added to the must. The second activity is to inhibit oxidative enzymes that would cause the juice to change colour and go brown.
During fermentation, it is important to control the temperature and oxygen concentration of the must. When the sugar concentration has reached about 10 g/L or less, usually in 7-15 days, the must is drawn off the pomace. In some cases, the wine may be allowed to remain with the skins and seeds for several days after the fermentation is complete in order to obtain wines with a high tannin concentration.
The processes that follow fermentation aim at achieving wine clarity and making that clarity stable from a physicochemical viewpoint. Examples of such fining reactions include the removal of tannic and/or brown polymeric phenols by protein-fining agents such as casein, albumin or gelatine, the absorption of wine proteins by clays such as the bentonites, and the elimination of unpleasant odours by copper sulphate.
Another important process involves wine filtration. This is a general operation which encompasses a wide range of conditions, from the partial removal of large suspended solids to the complete retention of microbes by perpendicular flow polymeric membranes. Most wines are subjected to fining and/or filtration processes, but only some wines containing high concentrations of ethanol and tannins are selected for ageing.
In general, this is used for red wines but some whites (e.g. Chardonnay) are also subjected to ageing. It is a very complex process which has many effects on the wine, and can be performed in two stages – bulk and/or bottle. Ageing in the bottle ranges from a few days to several years and is dependent on wine type. Generally speaking, there is no bulk ageing for white wines and the period of bottle ageing lasts for some months (never more than one year). For young red wines, bulk and bottle ageing can take place over a very short time period (maximum two years) while for particular red wines, ageing can take a very long time.
The absence of absolute control over the entire process of grape growing and producing wine has always been part of the charm of winemaking. However science and technology are gradually eroding the inherent mysteries. Science has had a long relationship with winemaking, from breeding new grape varieties to improving the fermentation process, and, most recently, advising on which vines to grow in a given location.
“A great wine is made in the vineyard”, and this starts with the quality of the grapes. Consequently, research is now beginning to focus on this aspect, selecting the optimal variety for a given location. As a result, not only winemakers but also scientists are turning their attention to how the interplay between geology, soil chemistry, biology and environmental conditions produces wines with complex and distinctive flavours in one area but not in neighbouring regions.
Geographic information systems (GIS) technology plays a huge role in the wine industry, using technology to create spatial maps that provide valuable information to differentiate how and where to grow grapes.
Technology now impacts every step in the winemaking process as well, from harvesting to sorting and much more. Temperature control is perhaps one of the biggest advances in modern wine technology. Winemakers are now able to monitor tank jacket temperature, must temperature and juice temperature. Sensors also permit the evaluation of the fermentation progress – Brix, pump status, fluid flow, differential tank pressure and temperature in real time – drastically automating a once-manual process. Experts have developed new forms of fermentation to help produce wine more efficiently and prevent it from spoiling.
Most people don’t realize how much chemistry goes into making a product that is supposedly just grapes and yeast. Along with the wide range of additives, winemakers today can custom order yeast that will produce wine with certain flavours or characteristics. Modern analytical tools, including mass spectrometry and gas chromatography, now allow scientists to investigate the role of various microorganisms to better understand the fermentation process. Various companies now offer a wide range of yeasts, enzymes and other additives to suppress or enhance certain reactions.
Other common winemaking operations include adding acidity with tartaric acid to compensate for the less acidic grapes grown in warmer climates, or adding sugar to compensate for the more acidic grapes grown in cooler climates.
Tannins, a substance found in grape skins, can be added to make a wine taste “drier” (less sweet) and polysaccharides can even be used to give the wine a “thicker mouth feel”, meaning the taste will linger more on the tongue.
Furthermore, understanding the role of oxygen in winemaking is a field that attracted particular attention by winemakers and scientists. Advances in protecting wine from oxygen have already permitted winemakers to make wines that a generation ago simply weren’t possible. Warm climate wine regions can now make whites and un-oaked reds with incredible freshness of purity of fruit, largely because of the availability of refrigerated stainless steel tanks and inert gases. But while protecting wines from oxygen has been a powerful tool for shaping wine style, the appropriate exposure to oxygen is also important for making some wines.
Fine wines’ complex flavours, aromas and bouquets are shaped by a number of factors related to raw material, additives and circumstances such as grapes and region, weather conditions, barrel oak, cellarage and methods of production. For example, micro-oxygenation (a process used in winemaking to introduce oxygen into wine in a controlled manner) imparts a barrel-aged flavour to wine stored in stainless steel. Micro-oxygenation affects colour, aromatic bouquet, mouth-feel and phenolic content.
Science is just one of the lenses we can use to examine wine with, and there’s still a great deal about wine that science can’t really explain. Most of the world’s great wines are not made by technicians, but by artisanal wine growers, working empirically. They observe; they experiment; they understand. Huge changes have taken place because of the understanding of the relationship between microbial growth in musts and wine, and the influence on wine flavour. Sadly, it has largely been used to make cheap wine more cheaply.
Winemaking is both an art and a science, and different climates and soil types will impact on a single grape variety. Many different styles of wine have emerged as a result of differing viniculture methods, and few winemakers would agree on just one “correct” method of wine making. We still don’t have a good scientific explanation for why certain wines are so fabulous, while a few hundred yards away, very similar-looking vineyards produce rather ordinary wine.
Each wine is unique. Soil, weather, geology, varietals, and the style of winemaking are all decisive yet variable factors that give each wine a unique character. However, to achieve the ideal combination of these characteristics, neither viticulture nor fermentation alone makes a great impact on the final product. We should not separate these two, but rather see winemaking as a holistic process.
Does technology make a better wine? Who knows? The notion of making better wine is of a subjective nature. Winemaking has many variables that ultimately affect overall quality. Clearly a distinction must be made as to the overall outcome. We all want to make better wine, but technology can contribute to the production of both bad and good wines – it’s all about how you use the tool.
Although technology allows winemakers to produce better quality wines, the continuing obsession with technically perfect wines is unfortunately stripping them of their identifiable and distinctive character. Whether it is the excessive filtration of wines, or the excessive emulation of winemaking styles, it seems to be the tragedy of modern winemaking that it is now increasingly difficult to tell an Italian wine from one made in France or California or Australia.
Technology is a highly useful tool, however it isn’t a substitute for human touch, taste, and intent. One must not forget that the great appeal of wine is that it is a unique, distinctive, fascinating beverage and different every time one drinks it.
Of course the prevailing rule of drinking is, and has always been, drink what you like, but have in mind that not all wines are as natural as they seem.