The last of a two-part article dedicated to the winemaking process. What happens after alcoholic fermentation? Behind the scenes of your favourite drink
I recently attended the London Wine Fair. What I enjoyed most (apart from the wines of course) was listening to passionate winemakers. From what I can tell, a winemaker is akin to a mythological creature – half poet, half artisan.
Much like the poet who agonises over their sonnet, trying to achieve a balance between structure and meaning – a good winemaker always has an overarching vision that guides them throughout the process. The winemakers’ goal is to produce the wine they dream. To do that, winemakers go through a series of decisions, starting from nature (environmental conditions and vines) and culminating with the bottled product.
Every decision in winemaking affects the style, taste and even the price of the wine. I covered the winemaking process up to alcoholic fermentation in the first part of my article. In this part, I will deal with the decisions that take place after fermentation has completed.
The following infographic details the major steps of winemaking.
Post-fermentation maceration
This is an optional step that only takes place in red winemaking. After fermentation has completed, a winemaker can decide to leave the fermented juice in contact with the skins for a variable amount of time (anything from 3 to 100 days).
Post-fermentation maceration (or extended maceration as it’s also referred to) primarily serves to enhance flavour and tannin extraction. For some grape varieties, winemakers have found that an extended period of maceration encourages a more supple and round tannic structure. This happens because over time the tannins undergo a polymerisation process. Their molecules bind, becoming bigger and less bitter.
The duration of the maceration usually depends on the grape variety and, above all, on the style the winemakers want to obtain. For example, in the Barolo area of Piemonte the traditional approach for nebbiolo wines is to undergo a long maceration period. This makes the tannins really strong and astringent. As a result, traditional-styled Barolo needs time for its structure to mellow. The modern approach envisages a shorter maceration period after fermentation. These wines are usually more accessible and can be enjoyed younger.
Rack-off lees
Only white wines undergo this optional step. When fermentation ends, the wine normally appears cloudy. This cloudiness is caused by dead yeast cells (called lees) and grape skin fragments which are still in the liquid. To remove these particles, some sort of clarification technique is used – typically racking (see my previous article on this topic for more details). The extent to which the wine is clarified at this stage is a winemaker decision.
Some winemakers may decide to leave some fine lees in contact with the liquid for a set time. This practice is called lees contact. If left alone, these small particles will settle at the bottom of the vessel forming hydrogen sulphide which would spoil the overall aroma of the wine. To avoid lees settling at the bottom of the vessel, winemakers usually use a technique called Bâtonnage or lees stirring. With the help of a long baton, the lees at the bottom of the barrel are periodically moved so that they fully mix with the wine.
Lees contact changes the body of the wine. It gives a richer texture and a denser mouthfeel. If lees contact is prolonged (typically more than 9 months), it also imparts flavours of its own. Bread dough, pastry, biscuits and a delicate toast-like undertone are typical. These flavours may sound familiar to Champagne lovers. That is because after the second fermentation in bottle, Champagne wines stay on their lees for several months.
Drain and pressing
These two steps are only relevant for red wine production. As you will remember from the first part of my article, for white wines pressing happens before fermentation. For red wines, draining and pressing take place after fermentation. Draining allows unpressed juice to separate from the cap (the mass of pulp, skin and seeds). After draining, more juice can be obtained by pressing the cap. The fractions obtained this way are usually richer in colour and tannins. For a complete description of the pressing phase, please refer to my earlier article.
Malolactic fermentation
Malolactic fermentation (MLF) is the reason for your big buttery chardonnays (such as old-style Californian chardonnays). Technically speaking, MLF is a chemical reaction that transforms malic acid into lactic acid. The former is tart (think a crunchy green apple), the latter soft and buttery. When a wine is subjected to MLF, its perceived acidity is lower and broader.
MLF is carried out by a strain of bacteria called Oenococcus Oeni. MLF usually occurs after alcoholic fermentation has finished (but it can take place at other times). It spans from two weeks to three months in duration. Since there are bacteria in the environment capable of transforming malic acid into lactic acid, MLF will naturally occur unless it is artificially inhibited. However, it is common for winemakers to inoculate controlled strains of Oenococcus Oeni to have more predictable and consistent results.
MLF is carried out for virtually all reds and for some whites. In white winemaking, whether to apply MLF is an important stylistic decision. If a winemaker wants to impart a lower and broader acidity to their wine, and add buttery or creamy flavours, then MLF is the way to go. Another reason why winemakers may want their wines to go through MLF is stabilisation. When a wine doesn’t undergo MLF, the reaction may take place anyway, later in the bottle. This would turn the wine cloudy, giving it an unpleasant sour aroma. Additionally, wines subjected to MLF are also more resistant to microbiological spoilage.
Nevertheless, there are circumstances where MLF should be avoided. For instance, when it’s important to preserve a high acidity in the wine (such as sweet wines). Another example is when the winemaking focus is to retain the original primary flavours of the grape. This last reason explains why most aromatic grape varieties, such as sauvignon blanc and riesling, do not normally undergo MLF.
Blending
In wine, blending is much more common than you would expect. In fact, almost all wines are blends. You might think that a “blend” is when you mix different grape varieties into the same bottle. In reality, blending is a much broader concept.
Winemakers can blend:
- different grape varieties – the most common idea of blending
- fruit coming from different vineyards. This routinely happens with most producers that buy grapes from growers
- wines that are vinified in different ways. For example, blending a percentage of wine from stainless steel with a portion of wine matured in oak barrel
- liquids coming from different pressing fractions, such as blending free-run juice with pressed wine
- wine from different vintages; non-vintage Champagne is made this way
As you can see, the possibilities are endless.
Blending can happen at any stage of the vinification process. However, in most cases blending takes place straight after fermentation or during the maturation process. You might wonder why winemakers blend their wines? There are four main reasons: balance, complexity, consistency and style.
Blending allows winemakers to even out undesirable characteristics to achieve balance in their final product, hence enhancing its overall quality. There are many ways that a winemaker can achieve balance. For example, free run juice can be blended with pressed wine to give more tannins to a red wine. To prevent oak flavours dominating the final wine, a winemaker might choose a portion of the wine to be matured in oak then blend this with another portion that sees no wood at all. In Bordeaux (a wine region where blends are the norm), merlot is added to the blend to moderate the austere character of cabernet sauvignon.
Strictly connected to balance is complexity. The concoction of different grape varieties (or different vinification processes) augments the aromatic complexity of a wine. Sticking to Bordeaux reds as an example, merlot provides flavours of plummy fruit, cabernet sauvignon – a pleasant stalkiness, petit verdot – a spicy note. For the same reason, the reds in Southern France are often blends. Grenache adds spiciness, syrah and carignan confer a touch of black fruit, while mourvedre gives meaty nuances.
Consumers normally expect to taste the same product regardless of variations in bottles, production batches or vintages. Consistency is important. Even when maintaining the exact same vinification process, the resulting wine may differ from case to case. That is due to slight differences in the raw material (grapes), variation in vats or oak barrels, etc. Blending everything together in large vats is usually just what winemakers need to smooth out inconsistencies.
Blending can also be carried out to achieve a particular style. Some winemakers’ top goal is to produce wines with a clearly recognisable house style, regardless of the variations that might occur from case to case, or from vintage to vintage. This is particularly true in Champagne. Top sparkling producers have a trademark style – and their objective is to produce, year in year out, wines that can clearly be associated with their brand. For this reason, many Champagne producers seek to create as many blending options as possible.
Maturation
The term “maturation” refers to the period of time after fermentation but before the actual consumption of the wine. Let’s bust a myth! Not every wine benefits from long maturation. In fact, 90% of the wines are meant for early consumption. By this I mean that most wines are intended to be drunk in the first one or two years after the vintage indicated on the label.
Another erroneous generalisation is that all premium wines can (and should) be aged. If the main objective of the winemaker is to retain and enhance the aromatic primary flavours of the grapes – then odds are the wine wouldn’t benefit from extended maturation (even if it’s a high quality wine). This is because with age, a wine tends to lose its fresh and fruity character and instead develops different types of flavours. As such, unoaked sauvignon blancs or Australian rieslings are normally intended to be drunk early – even their premium versions.
So when does a wine benefit from long ageing? Generally speaking, when two conditions are met. Firstly, the wine needs to have structure. That is, a high level of tannins, acidity and/or alcohol. Secondly, the flavours in the wine need to be concentrated, so that they can evolve in an interesting way over time (typically, primary fresh fruit aromas fade, giving way to secondary and tertiary flavours). Some notable examples of wines that age splendidly include: great Bordeaux wines, top-notch Burgundy, Barolo, Brunello di Montalcino, quality Rioja, more concentrated expressions of cabernet sauvignon, Northern Rhone syrah and Vintage Ports. Even though this aspect is often overlooked, certain styles of white wines can also age beautifully. Since white wines don’t have tannins to act as preservatives, acidity is paramount. Examples of age-worthy whites include: white Burgundy, top-quality German rieslings, Vouvray from Loire and white Bordeaux (both dry and sweet) A good example of ageable sweet white wine is Sauternes.
Maturation can be either anaerobic or aerobic. This is an important distinction as it hugely impacts the chemical reactions happening in the wine over time.
Anaerobic maturation means that the wine ages without being in contact with oxygen. This happens if the maturation vessel is airtight (implying it does not allow air to come in contact with the liquid). Stainless steel and concrete vats are inert and airtight. Typically wine is stored for a limited time in those vessels – before being bottled.
The main container for anaerobic maturation is actually the glass bottle. Producers can bottle and store their wines in their venues for years before releasing them (most Rioja producers do this for Reserva and Gran Reserva wines). Alternatively, wine lovers can purchase bottles and store them for years (hopefully under the right conditions) before uncorking their matured wines.
Irrespective of the particular vessel used, anaerobic maturation has two important characteristics: lack of oxygen and no flavour imparted by the vessel. The extent to which these characteristics exist have an enormous influence on the way the wine develops over time. In anaerobic maturation, the wine will not feature secondary flavours (such as roasted nuts, cigar box, clove, etc). Instead, the wine will maintain a purer bouquet where fruit dominates. Fresh fruit aromas will give way to cooked and preserved fruit. In red wine, think red (or black) fruit jam, prunes and dates. In white wine: dried apple skin, dried apricot and marmalade. Apart from this fruit development, other aromas emerge during anaerobic maturation, these include: petrol, kerosene, toast, hay, mushrooms, honey for whites; while in reds, flavours such as leather, earth, mushroom, tobacco, savoury and meat will emerge.
Aerobic maturation takes place in the presence of oxygen. Contact with oxygen (unsurprisingly) triggers oxidation – a chemical reaction which changes the structure and the aromas of the wine. Oxidative wines have a richer texture, greater complexity and a characteristic aromatic profile. These wines are less fruity but acquire savoury, toasty and earthy notes.
Oxidised vs Oxidative
In wine jargon, oxidised and oxidative denote different things – even though each has one thing in common – oxygen. An oxidised wine is a faulty wine: the liquid has been unintentionally and harmfully been exposed to oxygen. Oxidised wines lose colour and fruity flavours and taste vinegary. While in an oxidative wine, the winemaker has deliberately decided to give the wine controlled exposure to oxygen. It’s a stylistic decision that affects the wine texture and flavours.
In aerobic maturation, wine is typically aged in some form of wood container. Oak is the preferred choice, both for historical and practical reasons. The use of wood to age wine for an extended period of time leads to a second major effect on the wine profile. Oak (like all wood) is not an inert vessel. It imparts its own specific flavours to the liquid contained within. With oak, things get a bit more complicated, so please bear with me.
The impact of oak maturation on wine depends on five main factors:
- Size of the wood vessel: smaller barrels impart more flavours to the wine, as proportionally more liquid is in contact with the wood
- Amount of time the wine is in contact with wood: as you can imagine, the more time the wine spends in contact with oak, the more the oak flavours are transferred to the wine
- The extent of previous barrel usage: new barrels impart more flavours than older barrels. A good analogy is to imagine a tea bag dipped into a cup of hot water. The first time the tea bag is used, it is powerful and imparts strong flavours. However, each time the tea bag is used, the strength of flavour diminishes
- The nature of the wood: generally two types of oak are used to build wine barrels: European and American oak. European oak tends to impart more savoury and toasty flavours (roasted wood, cigar box), while American oak gives more sweet aromas (vanilla, coconut, etc.)
- The level of toastiness in the barrel: the way barrels are made matters. To create a barrel, wood staves are heated over an open fire, bent and held together with iron rings. During this process, the wood can be “toasted” to different degrees. A barrel that is highly toasted will confer more mocha and butterscotch nuances.
The combination of the oxidation and wood processes described above affects the flavour of wine in recognisable way. A wine that is matured in oak assumes a complex array of flavours: toast, toffee, butterscotch, cloves, nutmeg, charred wood, chocolate, coffee, cinnamon, vanilla.
The use of oak in maturation depends on several factors: grape variety (some varietals don’t cope well with wood), intensity of flavours (more concentrated wines can withstand oak without losing their original character) and – above all – the winemaker’s vision. Most of the times, as everything is in wine, the winemaker is seeking balance.
Maturation is one of the stages where winemakers’ stylistic choices most clearly impact the wine’s character. There are some winemakers that avoid oak like a bad disease, claiming it covers the authentic flavours of wine. Others heavily use new oak and extensive maturation in bottle to accentuate secondary and tertiary flavours over fruity ones. This is particularly true for certain wine styles (for instance: Sherry, Madeira, Vin Jaune in Jura) where deliberate oxidation is the norm and an integral part of the wine’s style.
Packaging
Before being released on the market, it is crucial that the wine is packed into a suitable container. The vast majority of wine is stored in glass bottles because they are cheap to produce, sturdy, air-tight and most importantly don’t taint the wine. Because of this, to date glass represents the best material for long wine maturation. Of course, glass bottles do also have their disadvantages. In particular, they are heavy, rigid and add a significant amount to the cost of transportation.
Regardless of the above, glass is not the only choice for wine storage. Plastic bottles, bag-in-box packs and cans are also viable alternatives. Plastic bottles (typically made using polyethylene terephthalate, or PET) are lighter and easy to transport. In recent years, bag-in-box wines (a plastic bladder encased in a card-box) have become more popular. The advantages of “Bag-in-box” is that they are light and can collapse after usage. However, both plastic and bag-in-box containers are not airtight – allowing oxidation. Further, they can impart unpleasant flavours over time. As a result, they are ideal for early consumption, but unsuited for wines intended for long maturation.
Wines in aluminium cans have been rising in popularity. Wine cans are popping up everywhere, and they seem particularly appealing among millennials and unconventional wine drinkers. Personally I have never tried a wine in a can, and to be frank the thought does not enthuse me. But I can recognise the main advantage of this format: size and convenience. A 750ml bottle might be too much for your mid-week drink, but you can crack open a can – and this will be the equivalent of a glass.
Bottles need a form of closure to keep it sealed until the wine is ready to be consumed. Most wines, as I mentioned before, are meant for early consumption. In those cases the choice of closure is not a big deal. However, if a bottle is intended for extended maturation the closure becomes an important factor. It’s fair to say that the choice of the closure is an important winemaking decision.
In cases where wine is intended to have a long maturation period, the bottle closure should allow the wine to mature positively over time. Different types of closures vary the amount of air (oxygen) that can pass into the bottle and come in contact with the liquid. A small and controlled entry of oxygen allows the development of tertiary flavours. Other closures, on the other hand, are completely airtight. In those cases, no oxidation will occur. The goal of airtight closures is to preserve the fruit aromas of the wine.
There are different types of closures:
- Cork: the traditional closure for wines, is still the most widely used. Cork is a porous material which allows a small quantity of oxygen to come into contact with the wine contained in the bottle. It’s the closure of choice for winemakers who prefer a balance between the primary flavours of the wine and the tertiary flavours developed over time. However, cork closures can come in different quality levels. The main disadvantage of cork closures is that they may suffer from a wine fault called cork taint. This wine fault is caused by a chemical (called trichloroanisole, or TCA) that imparts mouldy and unpleasant cardboard-like flavours to the wine.
- Synthetic corks: these are generally made from some sort of plastic. Synthetic corks are not subject to cork taint. They are cheaper and don’t normally expand or contract with temperature fluctuations – but glass wine bottles do. This lack of expansion and contraction can result in synthetic corks not maintaining the tight seal needed for the bottle. Consequently, oxygen can seep into the wine, spoiling it. This risk is why synthetic corks are normally reserved for wines destined for early consumption. Recently a few premium synthetic corks have been produced, designed to behave like natural corks but their adoption is still limited.
- Screw caps: these were originally championed by some New World countries (notably Australia and New Zealand) as a reaction to corked bottles. Screw caps do not taint the wine and they are completely impermeable and airtight. This means that while a bottle remains sealed, no oxygen will enter the wine. The lack of oxygen means any maturation in the bottle is completely anaerobic. For this reason, screw caps are the preferred choice for winemakers wanting to preserve the primary fruity flavours of their wines. In recent years, a new generation of screw caps have become available, which allow a small flow of air to enter the bottle. Some countries (especially in the Old World) still see screw caps as a “mark” of cheap wine. This stigma has inhibited the proliferation of screw caps. In reality, there is no correlation between the quality of a wine and the nature of its closure.
- Vino-seal (also known as glass stoppers): a couple of glass manufacturers produce these closures, which are usually made from a combination of plastic and glass. Vino-seals claim to create a hermetic seal that prevents oxidation. Their use is not very widespread.
Release
After the wine is bottled and labelled, it is technically ready to be sold into the market. In practice, some producers may decide (either due to stylistic reasons or regulation constraints) to keep the bottles for a while (allowing them to mature) before actually releasing them to the public.
When wine is put on the market, we – the wine drinkers – can finally buy it. As mentioned before, the vast majority of wines are intended for early consumption. For the small minority of wine that can be aged, drinkers can decide how long to keep the wine before actually drinking it. There is no standard ideal maturation period for a wine. It really depends upon the grapes, wine style, producer and, above all, personal preference.
Conclusion
And so ends our journey into winemaking. In my two-part article I tried to condense a few millennia of wine history. Over time, winemaking has evolved considerably. However the ultimate aim is the same as it was thousands of years ago – to transform humble grapes into noble wine.
Knowing the steps that lead to the production of your favourite drink will help you understand why a wine is what it is. Every aspect of a wine – flavours, structure, style, price – is ascribable to a combination of environment and winemaking.
I hope this article has triggered your enthusiasm for wine knowledge. A keenness I aspire to foster with the upcoming contributions to the knowledge section of Wine and Other Stories! Eager to know more? If like Aerosmith, you “don’t want to miss a thing”… why don’t you subscribe to my newsletter?
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