Finishing and Packaging Flashcards
What happens in the 4 months when getting your wine ready for bottling day?
4 months to 8 weeks ahead
Assemble final blend
Full chemical analysis – alcohol, residual sugar, free SO2, etc.
8 weeks ahead
Final adjustments: alcohol, acidity, tannins if desired
6 weeks ahead
Protein stability trial and if necessary fine with bentonite
4–6 weeks ahead
Test for tartrate stability and, if necessary, treat
4 weeks ahead
Check protein stability and tartrate stability again, treat as necessary
1–2 weeks ahead
Add sweetening agents e.g. grape concentrate, if using (for mouth feel and finish)
72-48 hour ahead
Test filterability of wine
24 hours ahead
Adjust free SO2
Bottling day
Adjust dissolved oxygen and CO2
During bottling
Check dissolved oxygen (to ensure no pickup) and SO2 levels regularly and keep sample of bottle wines for quality assurance purposes
Explain Sedimentation?
If wine is stored in cool cellar conditions, it will begin the process of clarification naturally, with suspended matter precipitating over time. The wine is allowed to stand and the particles with higher density than wine will form a sediment at the bottom of the container. The wine can then be racked off, leaving the sediment behind.
The number of rackings required depends on the size of the containers being used and the available labour. The larger the storage vessel, the greater the number of rackings required to avoid a thick layer of sediment.
Some premium wines are clarified only in this way. Some winemakers believe that clarification by sedimentation avoids the potential loss of texture and flavour that may occur if the wine is fined or filtered.
As sedimentation takes time, this has a cost as the wine cannot be sold until it is ready to be released. This means that sedimentation is usually only suitable for premium or super-premium priced wines. However, if a wine is to be barrel-aged, then sedimentation will happen as part of the barrel ageing process.
In many cases, the winemaker will accelerate the process of clarification. In high volume production where the speed of processing wine is financially important, the wine will be clarified by a combination of the following options.
Explain centrifugation?
This is a rapid process that spins the wine at high rotational speed to clarify it. It can replace depth filtration and allow early bottling. It is very effective with wines with a lot of matter in suspension. It is only practised in high-volume wineries to spread the considerable cost of buying the machine.
Explain fining and the different fining agents?
Fining is a procedure in which a fining agent is added to speed up the process of the precipitation of suspended material in the wine. Fining agents can be of protein or mineral origin. Fining removes a small proportion of unstable colloids (microscopic particles too small to be removed by filtering) from the wine. It helps to clarify the wine and to stabilise it against the formation of hazes later in the bottle.
Winemakers conduct laboratory trials before using fining agents to ensure that the minimum effective amount is used. They then compare the fined sample with the original wine before proceeding. Many fining agents can remove positive compounds from wine or make the wine unstable when too much is added (over-fining) and therefore it is important to only add the minimum effective amount.
In addition to clarifying the wine, each fining agent has particular properties that can offer solutions to problems such as the removal of harsh tannins in red wines or browning in white wines. The fining agent must have the opposite charge from the wine colloid to be removed. The fining agent and the colloid attract each other and form a solid large enough to be removed by racking or by filtration.
There are three categories of common fining agents:
- those that remove unstable proteins
- those that remove phenolics that
- contribute undesirable colour and bitterness those that remove colour and off-odours.
Fining agent that removes unstable proteins
Must and wine contain grape-derived proteins. It is not necessary to remove these in red wines as they bind with tannins, precipitate naturally and are removed when the wine is racked. However, the proteins in white and rosé wines can agglomerate into a visible haze if warmed up (e.g. in transit). This would be seen as a fault. As a result, these wines are often fined with bentonite.
Bentonite
– A form of clay which adsorbs (holds molecules of a gas, liquid or solute as a thin film on the outside surface or on internal surfaces within the material) unstable proteins and unstable colloidal colouring matter. It has a minimal effect on the flavour and texture of wine. It does lead to some colour loss in red wines and produces large amounts of sediment, and so wine is lost when it is racked off.
Fining agents that remove phenolics that contribute undesirable colour and bitterness
The fining agents listed in this section may be used in conjunction with bentonite for their own properties and to avoid risk of over-fining (which in itself could make the wine unstable).
Egg white
– Due to its protein content, egg white is often used in fresh or powdered form. It
tends to be used for high-quality red wines because of its ability to remove harsh tannins and clarify wine. It is gentle to the wine. As it is an allergen, it must be declared on the label if the wine is sold in the EU, and other territories if present above a specified limit.
Gelatin
– A protein collagen extracted from pork that aids clarification, removes bitterness and astringency in red wine and browning in white wine pressings. It must be added in the smallest effective amount as it is easy to over-fine with gelatin, stripping flavour and character, and creating the risk of a protein haze forming later. It is not suitable for vegetarian wine as it is derived from animals.
Casein
– A milk-derived protein that removes browning from white wines and clarifies wines to some extent. It must be declared as an allergen on the label in some territories.
Isinglass
– A protein collagen that very effectively clarifies white wines, giving them a bright appearance. The smallest effective amount must be added to avoid potential for the formation of a protein haze later and the creation of a fishy smell. It is not suitable for vegetarians as it is derived from fish bladders.
Vegetable protein products
– These are derived from potato or legumes and are suitable for vegan-friendly wines.
PVPP
– Polyvinylpolypyrrolidone is an insoluble plastic in powder form that removes browning and astringency from oxidised white wine. It is a gentler fining agent than charcoal. It is rarely used on red wines, but can reduce astringency and brighten the colour.
Fining agent that removes colour and off-odours
Charcoal
– This removes brown colours (e.g. to create Pale Cream Sherry) and some off- odours. Care has to be taken as charcoal over-fines easily removing desirable aromas and flavours. One option is to treat only one batch of the affected wine and then blend it with the rest of the wine to reduce this effect.
Explain the different ways of filtration?
Filtration is a physical separation technique used to eliminate solids from a suspension by passing it through a filter medium consisting of porous layers that trap solid particles, thus making the liquid clear. Filtration is the most common way of clarifying wine.
There are two main types, depth filtration and surface filtration.
DEPTH FILTRATION
This method of filtration traps particles in the depth of the material that forms the filter. It can cope with fluid with many particles in it; for example, wine that has just been pressed or lees. Small particles are trapped within the many irregular channels through the filter. This type of filter does not block easily; however, it is not absolutely reliable because, if too much pressure is applied or if the filter is used for too long, some particles will make their way through the filter. In other words, it is not an absolute filter.
Diatomaceous earth – The most common form of depth filtration is by using diatomaceous earth (‘DE’, also known as Kieselguhr), which, once it has been processed, is pure silica and inert:
- Rotary vacuum filters use this method to filter very thick and cloudy wine (e.g. wine mixed with lees). It is an oxidative process as the drum is exposed to air.
- Enclosed DE filters do the same job, but can be flushed with an inert gas (e.g. nitrogen) to avoid oxidation taking place.
- DE comes in a range of particle sizes and thus can remove large or very small (e.g. yeast) particles.
Used DE must be disposed of responsibly, which adds an additional cost.
Sheet filters – These are also known as ‘plate and frame’ or ‘pad’ filters. The wine is passed through a sheet of the filtering material. The more sheets there are in the filter, the quicker the wine can be filtered because any portion of wine only passes through one sheet.
Very fine graded sheets can be used to remove any remaining yeasts at bottling.
Sheet filter systems require investment initially (the frame must be very robust to withstand the pressures involved), although the cost of filter sheets is low. Trained personnel must operate them to work properly.
SURFACE FILTRATION
A surface filter stops particles that are bigger than the pore size of the filter from going through. They are often termed absolute filters. There are two types of surface filter:
Membrane filters
– These filters, sometimes also called cartridge filters, catch particles that will not go through the pore size of the filter. They are slower than using a depth filter as the pores are smaller, often less than 1 micron. For the same reason, wine must be pre-filtered first (e.g. by depth filtration) as, otherwise, membrane filters can easily get blocked. They are usually used as a final precaution immediately before the wine is bottled to ensure that the wine is completely clear and microbiologically stable. This is sometimes called sterile filtering, but this is not entirely accurate; the point is that yeasts and bacteria have been removed and therefore the wine is microbiologically stable. In contrast to depth filters, the initial investment is small, but the cartridges are expensive. This is a very common form of filtration during the bottling/packaging process.
Cross-flow filters
– These are also known as tangential filters. They allow wine to pass through the filter while uniquely cleaning the surface of the filter as it works. Solid particles cannot pass through the filter. Cross-flow filters can filter wine with a high load of particles or lees very quickly. There are no replacement sheets, cartridges or earth to buy or dispose of. However, the machines are expensive, making them more suitable for large and or well-funded wineries
Explain the various types of stabilisation?
The term ‘stabilisation’ is used to refer to several winemaking interventions which, if not carried out, could lead to undesired effects in the finished wine. This includes tackling the potential for unwanted hazes, deposits in the bottle and rapid changes in the wine (browning). Tartrate stability, fining and filtering all contribute both to clarification and stabilisation.
PROTEIN STABILITY
Fining with bentonite is the key procedure to ensure protein stability.
TARTRATE STABILITY
Tartrates are harmless deposits of crystals that can form in the finished wine, principally potassium bitartrate and, less frequently, calcium tartrate. As many customers will regard these crystals as a fault, all high-volume winemaking and many smaller scale operations will seek to prevent this from happening. There are several options for the winemaker:
Cold stabilisation
– Traditionally, this problem was dealt with to some extent by the wine being kept in a cold cellar for months through the winter. More reliably wine can be held at -4°C (25°F) for around eight days so that the crystals form before bottling (because tartrates are less soluble at cold temperatures) and can then be filtered out. Cold stabilisation requires the equipment and the cost of energy to refrigerate the wine. Colloids must be removed by fining before this process as they could prevent the crystals from forming at this stage. This process only removes the more common potassium bitartrate, not calcium tartrate.
Contact process
– This is a quicker, continuous, more reliable and cheaper form of cold stabilisation. Potassium bitartrate is added to the wine and speeds up the start of the crystallisation process. Wine is usually cooled to around 0°C (32°F) and after one or two hours the resulting crystals filtered out.
Electrodialysis
– This process uses a charged membrane to remove selected ions. After high initial investment, the total costs are lower than cold stabilisation and the process uses less energy and is faster. It removes both potassium and calcium ions and, to a smaller extent, tartrate ions. It is allowed in the EU and other territories for tartrate stabilisation.
Ion exchange
– This process does not remove tartrates, but, instead, it replaces potassium and calcium ions with hydrogen or sodium ions, which will not drop out of solution. This process is not allowed in some territories as it replaces the potassium with sodium, which is not conducive to health. However, the resulting levels in wine are well below the legal limit.
Carboxymethylcellulose (CMC)
– This cellulose is extracted from wood and prevents tartrates from developing to a visible size. CMC is widely used on inexpensive white and rosé wines, but is not suitable for red wines as it reacts with tannins (rendering it ineffective) and causes haze. It is much cheaper than chilling. CMC keeps wines stable for a few years.
Metatartaric acid
– Adding this compound prevents the growth of potassium bitartrate and calcium tartrate crystals, reducing the need for cold stabilisation. However, the compound is unstable, and its positive effect is lost over time, especially when wine is stored at high temperatures (25–30°C / 77–86°F). It is a quick and easy process that tends to be used more for red wines as for white and rosé wines CMC is more effective and long-lasting.
MICROBIOLOGICAL STABILITY
Wines with residual sugar are potentially liable to start to re-ferment in the bottle. This can be dealt with by removing yeast through sterile filtration. The alternative is to add sorbic acid and SO2, which inhibits yeast from growing. A drawback is that some people can smell the effects of sorbic acid at very low levels. (This has become less prevalent as a method since the widespread availability of sterile filtering.)
Very few microbes can live in wine with its low pH and high alcohol levels. Exceptions include lactic acid bacteria and Brettanomyces (a spoilage yeast). Wines with lactic acid bacteria where malolactic conversion has not been carried out or completed are liable to malolactic conversion starting up again in the bottle. (This would result in cloudiness in the bottle.) The solutions here are to ensure that malolactic conversion has been completed or filtering the wine to remove the bacteria. If Brettanomyces is a problem, wine can be treated with DMDC (dimethyl dicarbonate, commercial name: Velcorin) before bottling, which inactivates Brettanomyces.
Explain finishing options?
Before final finishing options are carried out, the winemaker will make a full chemical analysis; this will measure, at least, alcohol, residual sugar and free SO2. In the light of this analysis, final adjustments will be made. Within the last few hours before bottling levels of dissolved oxygen and CO2 will also be checked.
ADJUSTING THE LEVEL OF SULFUR DIOXIDE
Winemakers routinely check the level of SO2 and adjust it before bottling. They must ensure that the level of SO2 is within legal limits. Both the total SO2 and the free SO2 are measured, the latter being the part that contains molecular SO2, which is the effective part. Further, the amount of molecular SO2 depends on the pH of the wine – the lower the pH, the more molecular SO2 is present and the more effective it is. Wines with lower pH therefore require lower amounts of SO2.
Many factors will affect the levels of SO2 in wines at the point of filling, including winemaking approach, wine style (white, red, sweet), pH and intended drinking period (early consumption vs cellar ageing). However, in general, the amounts of free SO2 are:
- white wine: 25–45 mg/l (lower than for red wines due to lower pH)
- red wine: 30–55 mg/l
- sweet wine: 30–60 mg/l
REDUCING DISSOLVED OXYGEN
Oxygen dissolved in wine can accelerate the speed of ageing of the wine and thus reduce its shelf life. If the levels of oxygen are found to be too high, it can be removed by flushing the wine with an inert gas to remove it, a process called sparging.
ADDING CARBON DIOXIDE
A small amount of CO2 may remain in wine after finishing and packaging. However, especially for inexpensive fresh white and rosé wines, some winemakers will prefer a tiny bit of spritz from CO2 in the bottled wine for added freshness. If desired, CO2 is added just before bottling.
Explain wine faults?
Most present-day wine is technically fault-free because of the care taken at every stage of the production process – sorting to exclude damaged or mouldy fruit, exclusion of oxygen at key points in the process, temperature control, scrupulous hygiene in wineries, stabilisation, final adjustment of SO2, fining and filtering and care over bottling. Nonetheless, some wine faults continue to be seen.
CLOUDINESS AND HAZES
Wines can be less than perfectly clear for several reasons. This can be due to the growth of yeast or bacteria in wine coupled with failure to filter adequately. The remedy is better hygiene in the winery, pre-bottling chemical analysis and, as necessary, filtering wine to remove yeast or bacteria before bottling. Alternatively, cloudiness may be due to poor filtering of wine (e.g. pumping wine at too high a pressure through a depth filter so that some unwanted molecules go through the filter).
Cloudiness can also be due to a protein haze where fining is not effective, where the wrong type of fining agent has been used or the wine has been over-fined (see Fining in Post-Fermentation Clarification). This results in unstable proteins remaining in the wine, causing it to go hazy after the wine has left the winery or is with the final consumer. The remedy is to fine correctly and conduct analysis after fining.
TARTRATES
Tartrates are colourless or white crystals in the bottom of bottle that can be mistaken for fragments of glass. This can be seen as a fault by consumers, while knowledgeable drinkers may know that this is a natural process triggered by low temperatures and is completely harmless to health and wine quality. Most inexpensive and mid-priced wines are stabilised before release from the winery, but occasionally this is not entirely successful.
RE-FERMENTATION IN BOTTLE
Consumers may regard visible bubbles or spritz in wine as a fault. If it is accompanied by cloudiness, it would indicate unwanted re-fermentation in the bottle, which points to a failure to stabilise and clarify/filter the wine adequately. Some wine styles purposely include a low level of spritz (e.g. Muscadet sur lie or Vinho Verde). Some inexpensive and mid-priced white wines will have a small amount of CO2 added before bottling to preserve and enhance freshness.
CORK TAINT
This is associated with a very unattractive, mouldy, wet cardboard smell, which additionally reduces the fruit character and shortens the finish of wines. For approaches to reducing or eliminating cork taint.
OXIDATION
This is the result of excessive exposure to oxygen either in the winemaking process or once in bottle or other container. The latter can be due to faulty bottling, poor quality corks or plastic closures, or simply keeping wine for too long if it is not of a quality to age. The effect is that the wine becomes prematurely brown in colour with a loss of primary fruit and then a vinegary smell.
VOLATILE ACIDITY
All wines have volatile acidity, but excessive amounts give a pungent smell of nail varnish and/or vinegar. This is due to activity of acetic acid bacteria, inadequate levels of SO2 and excess exposure to oxygen. The threat can be reduced by sorting fruit to exclude damaged grapes, scrupulous hygiene in the winery, keeping vessels topped up, careful racking (to avoid excessive exposure to oxygen) and maintaining adequate SO2 levels.
REDUCTION
Reduction is associated with sulfur-like odours that range from onion to rotten eggs. The smells are caused by high levels of volatile, reductive sulfur compounds. Depending on the sulfur compounds present and concentration of these compounds some of their aromas (e.g. struck match and smoke) can give complexity to wines. However, at higher concentrations they produce undesirable aromas (e.g. rotten egg) that will always be regarded as a fault. These sulfur compounds can be produced by yeast under stress (due to low nitrogen levels) in the winemaking phase. Reduction also can be due to the near complete exclusion of oxygen during ageing in closed vessels, especially when lees ageing. Sometimes these odours evolve when wine is closed with the impermeable type of screw cap.
Reduction can be avoided by ensuring yeast has sufficient nutrients and oxygen, and that the must is at an adequate temperature. SO2 may need to be lowered, especially if the closure used allows very little oxygen ingress.
LIGHT STRIKE
Light strike is caused by UV radiation and certain wavelengths of visible light reacting with certain compounds in the wine to form volatile sulfur compounds, giving odours such as dirty drains. Wines that are left in direct sunlight are most at risk, but wines that are placed near fluorescent lighting e.g. in displays in retailers are also at risk. Choice of packaging can also be a factor. Wines packaged in clear glass are most likely to be affected, whereas dark glass (green, and particularly brown) provides more protection.
BRETTANOMYCES
The activity of Brettanomyces yeast produces a range of off-aromas from animal, spicy or farmyard smells. Some tasters think it can add complexity to red wines if at a low level. At higher levels it is clearly a fault in which the off-flavours dominate, fruity flavours are reduced and the acidity/tannins of wine becomes more prominent.
Once it has occurred in a winery, Brettanomyces is difficult to eradicate, especially as wood can host the organism and be very difficult to clean effectively. It can be present in old or new barrels.
The keys to avoid Brettanomyces are:
- excellent hygiene
- maintaining effective SO2 levels
- keeping pH levels low and keeping the period between the end of alcoholic fermentation and malolactic conversion as short as possible so that SO2 can be added as soon as possible.
What packaging options are there for wine?
Glass bottles finished with cork remains the most popular package and closure for wine. However, the winemaker must pay particular attention to oxygen management when packaging and choose the packaging and closure for the finished wine. Considerations include its place in the market (intended for early sale and consumption or as a wine that potentially may have a long life ahead of it) and the markets in which it will be sold.
OXYGEN MANAGEMENT WHEN PACKAGING
In addition to maintaining high standards of hygiene, the most important consideration when bottling or filling other containers is oxygen management. This is because the amount of oxygen in the final container will determine the shelf life and expected development of the wine. Too much oxygen will lead to premature browning and oxidised characters (loss of fruit, development of off-flavours including bruised apple). Too little oxygen may lead to reductive characters (e.g. onion, rotten eggs).
The total package oxygen of a wine is the combination of:
- the amount of dissolved oxygen in the wine
- the oxygen in the head space (below the cork or other closure) – usually the greatest contributor
- the amount of oxygen in the cork or other closure
- the oxygen transmission rate (OTR) of the cork or closure.
Because of all these factors, winemakers are paying increasing attention to limiting oxygen uptake in filling bottles or other containers (e.g. by flushing the head space with an inert gas before closing the bottle) and to the OTR rates of the closures chosen.
OPTIONS FOR PACKAGING
In most markets glass bottles are still the overwhelmingly preferred option for the packaging of wine. The two main exceptions would be:
- producer markets (e.g. France) where inexpensive plastic (PVC) containers are used to collect wine from a local winery for short term storage and early drinking
- the importance of bag-in-box in some markets (50 per cent and more), such as the Swedish market.
Glass
The advantages of glass are:
- It is an ideal container for wine as it is made of inert material that conveys no taint to the wine and is impermeable to oxygen.
- Bottles can be delivered to wineries in a near sterile condition, having been shrink- wrapped when still hot.
- It is inexpensive to manufacture and comes in a range of colours.
- In principle it is 100 per cent recyclable, but some colours are easy to recycle, others less so.
- Glass remains the best option for the ageing of wine as it is impermeable to oxygen.
However, there are significant disadvantages too:
- Glass has a high carbon footprint initially because of the heat needed to manufacture it.
- It is heavy to transport, again contributing to its carbon footprint, especially if it is transported thousands of miles to its final market.
- It is fairly fragile.
- Glass bottles are rigid; therefore, once a bottle of wine has been opened, it is subject to rapid oxidation.
- Wine packed in clear bottles can be spoiled by light strike from fluorescent (e.g. in supermarkets) and natural light, producing sulfur-related off-aromas. Green bottles give better protection and brown still better.
Plastic PET (polyethylene terephthalate) is a form of plastic that is light (about 1/8th the weight of glass), tough, inexpensive and, in principle, recyclable. It must be lined with a barrier to oxygen if it is to be impermeable and therefore give a reasonable shelf life. PET can be used for range of sizes, including standard bottle size or the single serve RTD (‘ready to drink’). It is well suited to wines with a limited shelf life and for quick consumption and in informal settings (outdoor eating, travel) or on planes where breakage is a hazard. Special filling equipment is required as the PET bottles are inflated at filling.
Bag-in-box
This consists of a cardboard box that houses a flexible bag inside. It is usually made of a very thin aluminium foil (which acts as a barrier to oxygen) covered on both sides by a suitable plastic. Another form of this bag is made from a plastic that gives some protection from oxygen and is resistant to cracking, unlike aluminium foil.
The advantages of this packaging include flexible pour size (one or more glasses), good protection from oxygen after wine has been poured (the bag collapses inside the box) and a range of sizes, 1.5–20 litres, suitable for home and commercial use. The boxes are easy to store and have low environmental impact (light to transport, can be recycled).
The wine must have a slightly higher SO2 level than in glass to counter oxidation, a low dissolved oxygen level, no head space and low carbon dioxide (the last to avoid the bag bulging).
Producers must use a high-quality tap as this is where most oxygen ingress occurs. Shelf life is in the range of 6–9 months depending on the quality of the manufacture, although the best may protect wine for up to a year. As noted, this is very successful in certain markets: Australia, where it was pioneered, and in Sweden.
‘Brick’
Often referred to as a Tetra Pak, after the leading manufacturer, this is made of paper card with plastic layers and an aluminium foil layer that excludes oxygen and light. The package can be entirely filled with wine, thereby excluding oxygen. It has been accepted by consumers at lower price points and does well in markets where price is a major driver (e.g. Germany). More attractive contemporary designs are appearing. The filling equipment is a big investment, and some producers outsource the filling of bricks.
Pouch
Pouches are similar to the bags inside bag-in-boxes. They are available in larger (e.g. 1.5 litre) and single serve sizes.
Can
The ring-pull can offers many advantages as a package for wine to be consumed early: it is light weight, robust, easy to open, impermeable to oxygen and recyclable. The aluminium has to be lined with a plastic to avoid being attacked by the acidity of the wine. Packaging companies continue to experiment with cans which may prove attractive in the RTD market. The filling equipment is a big investment, and producers will generally outsource the filling of cans.
What options for closure do exist?
All containers used for wine need a closure. The ideal closure would combine the following properties:
- protect the wine from rapid oxidation
- be inert so that it does not affect the quality of the wine adversely
- be easy to remove and to re-insert
- be cheap, recyclable and free from faults.
Cork continues to be the most popular closure (at around 60 per cent of wine bottles), but it now has several competitors. The most common closures for bottles are:
Natural cork
Cork is light, flexible (while requiring a specialised tool to remove it), inert (but can house harmful fungi) and comes from a renewable, natural resource. It mainly has a very positive image in the eyes of consumers and opening a bottle with a corkscrew is seen as part of the enjoyment of wine.
Cork comes in a range of length and quality, and a winemaker must decide what is appropriate to the wine and its intended price. Shorter, lower-grade corks are cheaper and may be used for inexpensive wines intended for short term consumption; better quality, longer corks are used for higher-priced wines that may be aged in bottle.
There have been two issues about natural cork. First, corks can taint wine through the creation of TCA (2,4,6-trichloroanisole) and other related compounds, resulting in an unpleasant smell of mould or wet cardboard that also suppresses the fruit character. The estimate is that this affects 3–5 per cent of bottles closed with cork.
Second, while cork is generally a good oxygen barrier, natural corks have variable rates of oxygen ingress. As a result, the same wine ages at different rates in the medium to long term.
The incidence of cork taint has led to two developments: the creation of alternative closures, and efforts by the cork industry to reduce or eliminate the incidence of cork taint. Approaches to the latter include:
- cleaning corks with stream extraction (championed by Amorim, the largest world producer of cork products)
- creating closures from recomposed cork particles that have been cleaned and reconstituted with a plastic; the result is a closure that looks and behaves like natural cork (championed by Diam) (This is a form of a technical cork.)
- much more rigorous quality control during cork production, including high-cost high-tech solutions (e.g. gas chromatography) to check for the presence of TCA
- an inexpensive solution by introducing a barrier between the cork and the wine; this is an impermeable membrane between the cork and the wine that gives a wrinkled appearance on the end of the cork and excludes any aromas reaching the wine.
Technical corks
These are made from cork that has been subjected to a manufacturing process. The cheapest option is the agglomerated cork in which cork granules are glued together. These are only suitable for inexpensive wines intended to be drunk quickly after purchase.
Synthetic closures
Popularly known as plastic corks, synthetic closures are made of food-grade plastic with a silicone coating. The cheapest are moulded closures; however, their relative rigidity makes them more difficult to re-insert in the bottle.
Moulded closures offer limited protection from oxygen ingress and therefore are only suitable for wines for consumption within months.
Extruded closures now come in a range of oxygen- ingress rates, with leading producer Nomacorc claiming that its top line is suitable for extended ageing in bottle.
A further issue with plastic closures is flavour scalping, the loss of some flavour intensity because plastic absorbs some flavour molecules. This process has been demonstrated in laboratory conditions, but it is not known if it occurs to an extent that would be perceived by a consumer.
Screwcap
The screwcap is an aluminium closure rolled onto the outside of a bottleneck that has been specially designed for this purpose. It therefore requires different closure equipment from in- bottle closures. The seal with the wine is a wad of either tin (impermeable to oxygen) or Saran (a form of plastic with low permeability to oxygen, better known for its use as cling film).
An issue with screwcaps, especially with near-impermeable tin linings, has been that wines can become reductive after bottling, with an unpleasant onion-like smell on first opening. To avoid this issue, winemakers intending to use screwcaps are adapting the final wine to have slightly lower SO2 levels.
Glass stoppers
Often referred to by the Vinolok brand name, glass stoppers are a closure made from glass, but where the actual seal is formed by a plastic ring. Wine can be stored for similar lengths of time as under other current closures (e.g. natural cork); however, special bottles must be used to ensure a perfect fit. The stoppers look attractive and are as expensive as top-quality cork, and therefore are only suitable for premium and super-premium wines.
Explain post-bottling maturation?
Many wines, usually those based on fresh, fruity flavours, are best consumed within a year of bottling as maturing them results in a loss of their primary fruit flavours. However, there are many wines that can develop positively in bottle for several years and are not at their best in the years immediately after bottling. Some notable examples include Vintage Port, premium German Rieslings and crus classés Bordeaux. Some PDOs (e.g. Chianti Classico Riserva DOCG) specify a minimum length of bottle maturation before the wine can be distributed and sold. Post-bottling maturation at the winery may increase costs, as the winery must have/build suitable storage conditions and pay insurance while the wine is in their ownership.
Glass bottles are the standard packaging used for wines that are intended for further ageing. Other types of packaging, such as plastic bottle or bag-in-box, are slightly permeable to air and therefore are suited to wines intended to be drunk young. Glass bottles are impermeable to air; however, it is possible for a small amount of air to ingress through the closure.
Similar to pre-bottling maturation, a small amount of oxygen can be positive, allowing the wine to develop slowly in bottle. Primary aromas become tertiary aromas, tannins soften, any aroma compounds from oak become better integrated and the colour moves towards brown and becomes paler in red wines and darker in white wines. However, rapid or excessive oxidation is perceived as a negative. By contrast, if the wine has been exposed to too little oxygen before bottling, this can lead to the formation of volatile, reductive sulfur compounds in the bottle. At low levels these compounds can give some aromas that may be perceived as positive, such as struck match and smoke. At high levels they give rotten egg and other unpleasant aromas.
It is widely agreed that any ageing time should be spent undisturbed in a cool dark place, with a constant temperature, ideally around 10–15°C / 50–59°F. There should also be constant humidity and, if sealed with cork, the bottles should be stored lying on their side, so that the corks remain moist and an optimum seal is maintained.
Explain quality control procedures in a winery?
HYGIENE IN THE WINERY
Virtually all modern wineries regard hygiene as a very high priority. High standards of hygiene give the winemaker the maximum chance of producing sound wine and of avoiding contamination from organisms that could spoil wine (e.g. spoilage yeasts).
New wineries are designed to facilitate cleaning. This includes the use of easy-to-clean stainless steel, hard non-porous floor surfaces that slope to aid drainage and equipment being located so that it can be reached to be cleaned. Particular attention must be paid to hard-to-reach areas: underneath equipment or dead-ends of pipes. Pores in oak continue to be a potential source of spoilage organisms.
There are three procedures for hygiene:
- cleaning – the removal of surface dirt
- sanitation – the reduction of unwanted organisms to acceptably low levels, typically with water and a detergent or other sanitising agent and/or steam; it is reckoned that for every litre of wine produced, 10 litres of water are used, most of this for hygiene purposes
- sterilisation – the elimination of unwanted organisms; for example, from high risk areas such as the filler heads of bottling lines – these can be sterilised with high strength alcohol or with steam.
Wineries have a detailed schedule setting out a programme of daily, weekly and monthly actions for cleaning, sanitation and, where applicable, sterilisation.
QUALITY CONTROL AND QUALITY ASSURANCE
‘Quality control’ in a winery is the set of practices by which the company ensures a consistently good quality product. ‘Quality assurance’ is a broader concept that includes quality control. It is the complete way a business organises itself to deliver a good product consistently and to protect itself from legal challenge. These include planning, management systems and the monitoring and recording of key standards from vineyard to bottling of wine. By having a comprehensive system in place, a producer can show that they have taken all reasonable precautions to produce a safe product for the consumer – and have the documentation to be able to demonstrate it.
HACCP HACCP (Hazard Analysis of Critical Control Points) is a common approach to quality assurance regarding significant threats to the safety of consumers and to the reputation of a wine company. It is a process in which the company identifies all the possible hazards that could affect final wine quality; in effect, everything that could go wrong. For each hazard, the HACCP document will state how serious it is, how it can be prevented and how it can be corrected.
To give an example, in a bottling line there is a possible hazard of glass breaking and ending up in a bottle of wine, a threat to the health of the consumer. In a highly mechanised winery, the preventive action plan would be to have a system in place to detect a broken bottle and to push out the next three neighbouring bottles automatically.
Certification to ISO standard
Wine companies seeking external verification of their quality standards can be audited against the standards by a recognised external body such as the ISO (International Organization for Standardization). The purpose of this to give assurance to all the parties down the supply chain: the wholesaler and the retailers who will sell the wine and, finally, the end consumer.
The ISO sets the standards (ISO 9000 and 9001) and separate certification bodies carry out the audits. External auditors from the certification body will review the company’s own quality management system, management structure, physical and human resources and how it measures, analyses and improves its performance. This is a rigorous process for which a professional fee must be paid.
In addition, many large retailers require a higher level of audit, which might also look at issues such as environmental policy or ethical trading. Multiple audits add further cost, both in terms of fees paid and in staff time.
Traceability
A formal system for traceability is necessary if a wine company is to:
- respond to and investigate complaints about wine; complaints can come from any point of the supply chain, including the final consumer
- improve its practice so that similar problems do not occur in the future.
Each consignment of wine will be given a lot number, which appears on the bottle. This is a requirement in the EU and many other markets. The lot number enables a company to trace back where the grapes came from, what additives have been used and what processes the wine went through. The winery must keep records of its activities at every point of its production, from the vineyard, through the winery and then in the transportation of the wine. Larger firms and those concerned about traceability will keep samples of every batch so that they can investigate what has gone wrong and compare returned bottles with their library of samples. Common problems include cork taint, tartrate crystals and faulty or missing labels.
Explain how transportation of wine works?
Historically, wine has been transported in animal skins, terracotta and, for centuries, in barrels. Bottling wine in the winery became an important means of quality control in Bordeaux, followed by other fine wine regions, starting in the 1920s. By this means, the producer could guarantee that the final wine was as the producer intended, rather than being at the mercy of possible blending or adulteration if shipped in barrel to the final market.
Today, the main options are transport in glass bottles or in larger containers, i.e. in bulk. Premium and super-premium wines continue to be bottled in the winery and transported in cases of individual bottles. However, for everyday wines there has been a rapid increase in transportation in bulk and bottling in or near the final market. This is particularly the case where very long journeys are involved.
Road and rail is used to move wine in containers of 24 000 litres from southern Europe to markets in northern Europe. Container ships carry wine from Australia, New Zealand, South Africa, Chile and Argentina to final markets in the northern hemisphere. This has given rise to very large scale and very high-quality bottling plants in or near final markets. The majority of exported wine is transported in bottle, however, wine transported in bulk makes a significant minority (currently 30-40% of volume). However, by value, bottled wine continues to dominate.
There are two types of container for the bulk shipping of wine: the more common flexitank, a single-use, recyclable polyethylene bag that fits into a standard container; and the ISO tank, a stainless steel vessel built to the ISO standard that can be reused many times and may have additional insulation. The flexitank bag is coated with a barrier to prevent taint from an external source and to reduce oxygen ingress. Insulated tanks with temperature control, known as reefers, are available, but at an additional cost.
The advantage of shipping wine in bottle is that the entire product – the wine, the bottling, the labelling and any external packaging – is controlled by the producer. The disadvantages are:
- the smaller amount of wine that can be shipped in one container and therefore a higher cost
- the financial and environmental cost of shipping the weight of glass as well as the wine
- potential damage to the wine due to high and fluctuating temperatures in transit, and potential spoilage of labels and packaging in transport
- the shorter shelf life of inexpensive wine because it is bottled earlier than if it were bottled in or close to the final market.
The advantages of shipping wine in bulk are:
- it is more environmentally friendly as one container can hold the equivalent of 24,000-26,000 bottles in liquid rather than 9000-10,000 filled bottles, reducing the carbon footprint of the wine
- it is cheaper, for the same reason
- the greater thermal inertia of a whole container filled with wine, which means there is less fluctuation of temperature; this reduces the effects of high temperatures in transport and therefore reduces the risk of loss of fruit and oxidation of wine in transit, which is particularly relevant for slow, long distance journeys that go through the tropics
- strict quality control: the key parameters of a wine (residual sugar, SO2, etc.) can be measured at the point of filling the container and again on emptying it
- the wine can be adjusted (e.g. level of SO2 can be adjusted) at the point of bottling close to the final consumer
- the shelf life of a wine can be extended as this is calculated from the time of bottling (e.g. shipping wine from Australia to northern Europe takes around eight weeks); this is particularly relevant for bag-in-box with its relatively short shelf life.
The main disadvantages of shipping wine in bulk are the loss of the direct relationship with the producer, and the transfer of business and employment opportunities from producer countries to the countries close to the final market. There have been protests, in particular from South Africa, complaining about the loss of business and of jobs. Shipping in bulk is only commercially viable for larger brands, for example those that will sell three or more containers per year.
