Wine Storage Guide

In a nutshell: Wine should ideally be stored at 8 to 15°C, no warmer. If the wine gets warmer, the delicacy is lost very quickly, the wine loses its elegance, finesse and fruitiness and is simply no longer good. This process is permanent and cannot be reversed by chilling again.

But beware: the ideal storage temperature differs from the ideal drinking temperature. The following illustration provides an overview:

But back to wine storage: of all the criteria to consider when storing wine, temperature is the most important - but why is that?

The reason, and this is where a little physical biochemistry comes into play, is the temperature-dependent reaction kinetics of the many substances that naturally make up wine. And there are a lot of them - the biochemist counts well over 1,000. That many? Most of it is water, then come alcohol, methanol and glycerine as the most important by-products of fermentation, then the various acids (tartaric, malic and lactic acids in first place), the unfermented residual sugars fructose and glucose, the minerals, especially potassium, calcium and magnesium. Then it gets exciting: aromatic substances, higher alcohols, volatile acids, aldehydes, ketones, flavonoids, anthocyanins and a multitude of phenolic components (or tannins) of all kinds - in the milligram or even nanogram range, but it is often precisely these that are particularly important for sensory perception.

Compilation of the most important ingredients of wines:

These are all natural ingredients that either come from the berries or the juice (primary ingredients), are formed during fermentation and malolactic fermentation (secondary ingredients) or are only formed during ageing (tertiary ingredients). This complex mixture is instable - especially the sensitive, fine aroma components, the higher alcohols, the natural ketones, aldehydes and the numerous phenolic components react with each other and ensure that the wine is constantly changing in terms of its appearance, smell, taste and aftertaste.

When it gets warmer, the ingredients react more intensively with each other; when it gets colder, the reactions slow down. This fact is well researched and is described by the so-called Arrhenius equation or reaction rate-temperature (RGT) rule, also known as van 't Hoff's rule. It describes the dependence of a reaction rate constant on the temperature.

It goes something like this: Starting from 10 °C and a shelf life of 12 months, it can be simplified to say that the reaction rate of the ingredients with each other doubles to quadruples with every further increase of 10 °C - and thus halves the shelf life or reduces it to ¼. At 20 °C, the reaction rate is therefore twice as high as at 10 °C, the shelf life is only 6 months, at 30 °C it is at least four times as high, the shelf life is only 3 months, at 40 °C it is already ten times as high or higher, the shelf life is only less than 1 month. In addition, as the temperature rises, reactions take place that do not occur at lower temperatures. Therefore, at temperatures above 20 °C, the tasty aromatic substances in the wine are lost very quickly and, unfortunately, irretrievably.

Therefore: store your wines in a cool place, below 15°C, so that you can enjoy them for as long as possible. This can be in the fridge, in a wine climate-controlled cabinet or in a special wine storage unit with a controlled temperature.

As we have already mentioned, temperature is the most important factor in wine storage, but what we have not yet discussed are temperature fluctuations. While it is relatively insignificant whether the wine is stored at 10 or 16 °C, it is in contrast quite significant if a wine storage has, for example, 17 °C in summer and then 9 °C in winter over the course of a year. Temperature fluctuations greatly accelerate the maturation of wine and have a negative impact on wine quality.

Ideally, temperature fluctuations in a wine storage should remain below 6°C throughout the year!

This can be explained as follows: when it gets warmer, the wine in the bottle expands slightly: with 3 °C more, in a normal 0.75-litre bottle, this is 0.5 ml. An overpressure is created. The magnitude of the overpressure depends on the temperature difference. The following table provides an overview:

The table shows the pressure increase with rising temperature. Analogously, the pressure decreases with a drop in temperature. The pressure values are then identical, just negative, and indicate a slight to strong vacuum in the wine bottle.

If the pressure difference is less than 100 mbar, a negligible pressure increase can be assumed. Between 100 and 200 mbar of pressure increase, the influence is slight. If the pressure increase due to the temperature change is between 200 and 400 mbar, a significant influence can be assumed. If the pressure exceeds 400 mbar, it can be assumed that the cork moves. In the opposite case, i.e., with a vacuum in the bottle, it can be assumed that the vacuum is balanced by gas diffusion into the bottle - the cork will not move. It is precisely this process, in which the vacuum "sucks" air into the bottle, that introduces new oxygen into the wine, accelerating aging and enabling reactions of wine components that negatively affect wine quality.

The table clearly shows that the residual air volume in the wine bottle has a very large influence on the internal bottle pressure. Winemakers now strive to keep the residual volume in the bottle as low as possible - around 6 ml is the average. The following rule of thumb provides an indication of how to roughly estimate the residual air volume:

1 ml of residual air in the wine bottle corresponds to approximately 0.3 cm in the bottle neck.

Then to the pressure increase. The pressure increase can also be calculated by yourself, the formula is relatively simple. First, the volume increase due to the temperature difference of the wine is determined:

The volume increase of the residual air volume is then determined in the same way:

The pressure increase is then calculated from the two volume changes:

If the temperature in the wine storage rises, there are two possibilities: if there is still some residual air in the bottle (which is usually the case), the expanding wine compresses the remaining air more and thus compensates for the volume increase. If this is not or only very slightly the case, the pressure becomes so great that the expanding wine pushes the cork out of the bottle a bit - the overpressure is thus reduced. The reason is simple: air can be compressed relatively easily. Liquids, however, cannot.

The smaller the residual air volume, the sooner a temperature increase will result in the cork being pushed out. This can be only a few millimetres to a centimetre – depending on the magnitude of the temperature increase.

So far, so good. But if it gets colder again, the volume of the wine decreases again – creating a vacuum in the bottle. Since the cork has a certain air permeability, the pressure equalization in this case almost always occurs through air diffusing into the bottle through the cork. This is easier than moving the cork further into the bottle. The vacuum equalizes slowly. However, new air (and thus oxygen) enters the bottle through the cork in this process. The cooling bottle literally sucks in the surrounding air. This gives the wine additional oxidation potential, accelerating the reaction of wine components: particularly disadvantageous is the introduction of new oxygen into the wine, as this leads to reactions of wine components that negatively affect wine quality – and which would not occur without it. It is precisely these that have a very detrimental effect on wine quality. The result: the wine ages faster than it would without temperature fluctuations, and its quality deteriorates. The temperature fluctuation thus acts like the bottle breathing, and each temperature fluctuation acts not only like an accelerator for the aging speed of the wine but also deteriorates the wine quality. Therefore, maintaining a very constant storage temperature is so important.

And what to do if it has happened? It is best to enjoy it immediately, as long as the aging and deterioration processes have not yet begun.

The ideal humidity for wine storage is between 45% and a maximum of 65% relative humidity. This is important even though humidity is completely irrelevant to the wine it-self. If it becomes too dry, it can cause a problem with the cork, which loses its elasticity due to dryness. A dried-out cork allows more air exchange, causing the affected wine to age faster. However, the problem of corks drying out is rather rare, as most corked bottles have a capsule that additionally protects the cork from drying out. For wines with a screw cap or synthetic cork, excessively dry storage is not an issue.

High humidity is more often a problem in wine storage

From 70% relative humidity, the growth conditions for mould fungi become increa-singly favourable, and from 80%, they are ideal! Mould fungi infest all organic materials, including wood and labels. If a wine cellar is too humid, the labels are covered with black spots or become unreadable within a few weeks. Wine bottles with such labels are disfi-gured, or it is impossible to tell which wine it is.

And what if the cork has mould?

This can happen - but it is not a problem. The fungus grows on the cork but stops as soon as it encounters alcohol that has diffused from the wine side of the cork into its depths. This stops the mould from growing further. As seen clearly in the image below, no metabolic products of the mould are found on the cork in the wine. Therefore, before opening a bottle with a mouldy cork, wash and scrub it with hot water, dry it, and then pull the cork. By the way, if the cork is old and brittle, it is best to use a two-prong cork-screw.

What does "relative humidity" actually mean?

First of all, humidity is the weight proportion of water vapour in the air. The matter of humidity is a bit complicated because the warmer the air is, the more water it can absorb. At 0°C, it's about 5 g in 1 m³ or 1,000 litres of air; at 10°C, it's about 10 g in 1 m³; at 20°C, about 17 g in 1 m³ - and so on. To have a temperature-independent measure of humidity, the relative humidity (abbreviation r.H.) was created. It expresses the percentage of air saturation with water, making it a better indicator than the absolute water content of the air. 70% relative humidity means that the air has absorbed 70% of the possible amount of water. The following table and chart illustrate the relationship.

Some wine storage rooms naturally have high relative humidity - typically these are cellars whose surrounding soil is moist and transmits this moisture to the room. To protect such rooms permanently from high humidity and associated mould infestation, either structural renovation or continuous air treatment with a dehumidifier is recom-mended.

Cool wine storage areas (whether cooled or naturally cool) into which warm air constantly penetrates (e.g., when entering) or which adjoin warm rooms, can also cause a mould problem. This is a known issue with wine storage in restaurants. What happens here? Two factors come together: as the warm air, which can hold more water, cools, the relative humidity rises, suddenly making water available for mould spores (from 70% r.H.), and mould growth begins.

The problem of condensation

During this process - warm air with high water content entering cold rooms - the dew point is undershot by the cooling (the dew point is the temperature at which the air is 100% saturated with water). The water condenses and becomes visible as water droplets. Everyone has experienced that a cold wine bottle, taken dry from the refrigerator and placed on the table, becomes wet after a few minutes. Water condenses wherever the temperature-related water saturation of the air is exceeded. This phenomenon occurs wherever the dew point is undershot. The fogged-up wine bottle is just one example; ty-pical spots are all areas where the transition from warm to cold is significant, such as the wine rack itself and the wall. These spots are usually hidden in rooms, less visible, and of-ten real breeding grounds for mould. This makes a room very unhygienic and un-healthy!

Condensation can also occur over large areas, such as on glass wine racks. Such fog-ging can ruin the beauty of a glass wine rack used as a display area.

For this reason, we offer our air-conditioned glass cabinet VITRUS and glazed design wine climate rooms. These products ensure that your wine collection is optimally stored without condensation affecting aesthetics or promoting mould growth.

Humidity, mould, and health

Mould not only destroys wine bottle labels and infests all organic materials, including the wood of wine racks, but it also poses a health problem. The following table provides an overview, sorted by the colour of the mould.

High humidity in the wine cellar (as in all rooms) should therefore also be avoided for health reasons.

Possible controls and remedies

Controlling humidity is simple; the measuring devices are inexpensive. To reliably avoid these humidity-related problems in wine storage, a well-designed air conditioning system combined with guided air circulation is the solution of choice. Why? Because air conditioners in air-conditioned rooms always produce drier air than would naturally oc-cur. This is because, as the air passes by the evaporator of the air conditioner, it cools be-low the set room temperature, reaching the dew point, and water is expelled. Thus, an air conditioner always acts as a dehumidifier (or water trap) and ensures a relative humidity of between 40 and 60% in air-conditioned rooms, the ideal range for wine storage. If the air from the air conditioner is then specifically directed to the critical condensation points in the room and warmed, the air can absorb water again, and such a wine storage room remains mould-free and the glass does not fog up or clears up after just a few minu-tes.

If the humidity problem in the wine cellar is not so severe, simple means like cat litter can help, as cat litter absorbs water from the surrounding air and stores it so that it is no longer available to microorganisms. From time to time, the water must be removed from the cat litter material: the best way to do this is on a hot summer day outdoors.

The worst thing that can happen is the exposure of a sparkling wine in a white glass bottle to direct sunlight for an extended period. After just a few days, the sparkling wine acquires a very unpleasant smell, reminiscent of cheese, sulphur compounds, cabbage or rubber – this is known as "goût de lumière". This defect, known as lightstruck flavour, was first discovered in champagne and called "Goût de Lumière". A sure protection against this lightstruck flavour is absolute darkness, i.e., the absence of light and a dark brown or even black bottle.

What is light?

Light is electromagnetic radiation and is energy-rich. Many of us have already felt it in the form of sunburn on our skin. Light is characterised by its visibility and its different wavelengths. Normal daylight, as we perceive it, is always composed of light of different wavelengths, which is why we perceive the light as white. Light with a short wavelength has a high wave frequency and is therefore more energetic than light with a long wavelength and low frequency. The following figure shows that visible light is only a small part of the electromagnetic radiation that we perceive as light.

Depending on the wavelength composition of the light we see, the light takes on a colour. Light with a higher proportion of short-wavelength light appears bluish, while light with a higher proportion of long-wavelength light appears yellowish or reddish. Adjacent to the spectrum of visible light, there are in the short-wave range UV rays and X-rays, and in the long-wave range, infrared radiation and microwaves:

What does light do to wine?

Riboflavin or Vitamin B2

Under the influence of light, in particular vitamin B2 or riboflavin is stimulated, which is responsible, among other things, for the yellow colour in white wine and sparkling wine. Wine contains 0 to 20 μg of riboflavin per litre as a natural ingredient. For information: riboflavin is one of the essential vitamins, which the human body cannot produce and must be supplied externally. The recommended daily dose for riboflavin intake, according to the DGE, is between 1.0 and 1.3 mg. In human metabolism, vitamin B2 plays a significant role. It provides the precursor for the enzymes of the respiratory chain and is thus involved in the conversion of nutrients into energy.

Riboflavin, involved among other things in the yellow colouring of wine, acts as a catalyst for reactions with various wine components. It is crucial that short-wave light in particular catalyses reactions with riboflavin that do not occur in the dark. The result of the reaction is compounds that make white wine or sparkling wine smell very unpleasant. Lightstruck flavour as a defect also exists in many foods, especially known in beer and milk. Especially in beer, lightstruck flavour has been well studied, the main component responsible for lightstruck flavour in beer is 3-methyl-2-buten-1-thiol (MBT). In beer, besides riboflavin, it is mainly hops that enhance the lightstruck flavour. Beers without hops do not develop lightstruck flavour.

Lightstruck flavour: wavelength is crucial

The most harmful components of light are the short-wave ones: UV radiation, violet and blue light – all below a wavelength of 500 nm. Higher wavelength light (yellow, orange, red) causes little damage.

Not only sunlight, but also light sources are harmful to wine:

Important: not only sunlight, but also conventional lighting such as neon or halogen lamps emit short-wave light, which is harmful to wine. Therefore, protection from sunlight is not enough to avoid lightstruck flavour in wine.

The figure shows the emission spectrum of a neon tube:

The following figure shows that halogen lamps also emit UV and short-wave light – although less than fluorescent lamps, but still significantly. Additionally, halogen lamps emit heat and have a very high power consumption.

LED lighting: the solution

LED lighting (Light-Emitting Diodes) has a very broad spectrum and the great advantage of being adaptable to specific lighting requirements. This is clearly visible in the lighting profile – furthermore, LED lighting is advantageous due to its low power consumption and low heat generation:

The following figure shows how versatile and specific LED lighting can be. The great advantage of LEDs is precisely this adaptability to specific lighting needs.

The following figure shows the emission spectrum of two different LED lights used in industry: it is clearly visible that the two LED lights emit very differently in the short and long-wave range.

The colour of the bottles: important protection against light

Coloured bottles absorb short-wave light differently depending on the colour. White glass lets through all the light and therefore has the greatest potential to negatively influence the wine, while dark brown glass absorbs most of the light and offers the best protection. The following figure shows this clearly: the green line represents green glass, the brown line represents brown glass, which lets through very little harmful short-wave light for the wine. Brown bottles reflect the light in the relevant range better!

The reflection of harmful light is an important reason why wine is marketed in coloured bottles, mainly green or brown.

Red wine is less susceptible to light damage than white wine and sparkling wine, as it mainly contains tannins and phenolic substances that protect the red wine from the negative influence of light.

Wine cellar and wine salesroom lighting today:

For wine storage and especially for wine salesrooms, there are now special LED lights that emit little or no short-wave light. This special lighting ensures that the lighting has no harmful influence on the wine. Naturally, it is ideal to store wine in the dark to maintain its quality in the long term. However, in salesrooms, appropriate lighting is essential. Our specialised LED lights offer a safe and efficient solution that protects the wine from harmful light. Additionally, we ensure that the wines are only exposed to light for a limited time in the salesroom to best preserve their quality. With these measures, we guarantee that every wine retains its characteristic aromas and quality while being attractively presented.

The longer we want to store a wine, the higher the requirements for the place where the wine is kept. The ideal location for storing the wine we have purchased depends primarily on whether we plan to enjoy it in the coming days or if we have bought it to keep in reserve or even for ageing. The storage duration thus largely determines the requirements for the place where the wine should be stored. If it’s just a matter of a few hours or days, it’s important that it is stored in a cool and dark place. If it’s for several weeks, it’s also necessary that the humidity level remains below 70%. If the wine is to be stored for several months or even years, the absence of odours and a calm storage environment are also important. The following table provides an overview:

Another aspect to consider is the potential storage locations, which can be characterised by their suitability for wine storage.

• Living spaces like the kitchen, storeroom, refrigerator, utility room, etc., are only suitable for short-term storage of a few days to a few weeks due to high temperatures and temperature fluctuations.
• Garages and hobby rooms are not suitable for wine storage as they can be subject to negative influences such as odours and vibrations. Wines should only be kept here for a few hours.
• Wine fridges are ideal for storing wine at the desired drinking temperature. This can be done without problems for weeks or months.
• Cellars or specially designed wine storage rooms are ideal for storing wines for several months or even years - provided they meet the requirements for temperature, relative humidity, odour neutrality, and freedom from vibrations.

The smell of the storage location can lead to wine spoilage.

Although it may not seem plausible at first glance: certain environmental odours can be absorbed by the wine in the bottle over time. Depending on the odour, it takes 2 to 3 weeks for it to diffuse through the cork into the wine, and for some odours like solvents, this can happen more quickly. This is because a cork is never completely airtight, but there is an exchange of substances through it. The illustration below shows this – the cork is permeable to gas molecules through its cell structure.

Corks have very different qualities and thus a very different gas permeability. This depends on the number of permeable cells in the cork, known as lenticels. The illustration shows different cork qualities – Extra is very good, suitable for wines that can be stored for a long time, while 2nd class is a cork with increased gas exchange, used for wines that are meant to be consumed young without storage.

The illustration below then shows the overall relationships that play a role in the cork and gas exchange.

Other types of closures, such as glass corks or screw caps, also allow gas exchange and thus odours to enter the wine. This is because odour molecules are detectable by humans at very low concentrations, which leads to continuous gas exchange through any closure – by the way, much more through corks than through a screw cap.

A very typical negative example: wine stored in a garage next to petrol and in contact with car exhaust fumes or in a hobby room alongside paints and solvents like turpentine will absorb this smell over time.

Wine ageing over years requires calm – vibrations make wines age faster.

Frequent shaking in the form of vibrations – for example, caused by a washing machine or a nearby railway line – accelerates the wine’s oxygen uptake from the remaining air volume in the bottle, thus speeding up the ageing of stored wines. The pleasant aromas of the wine decrease, especially in the case of frequent vibrations in the wine storage area. A frequently mentioned problem with vibrations or periodic shaking in red wines is the stirring up of the red wine sediment. The sediment, which can sometimes be a cohesive mass, breaks into smaller pieces. However, this sediment destruction has far less negative impact on the wine quality than the accelerated ageing due to biochemical reactions of the components.

Recent research has shown that the acceleration of wine ageing through targeted micro-vibrations can also have positive effects on wine quality. Source: Effects of Microvibrations and Their Damping on the Evolution of Pinot Noir Wine during Bottle Storage, Simone Poggesi, Vakarė Merkytė, Edoardo Longo, and Emanuele Boselli in Foods, 2022 Sep; 11(18): 2761.

When we want to buy a wine rack, there are almost infinite possibilities - and the choice of material plays a crucial role: we can choose between four materials: wood, metal, stone, and plastic.

First of all, wood:

Wood is simply the perfect raw material for anyone who wants to combine sustainability with a natural, stylish touch in their wine cellar. Wood is a renewable resource that helps protect our environment and allows us to lead a more sustainable life. For many, wood is the most natural and best choice for their wine rack or wine storage. No wonder wood is the most popular material for wine racks! Wine and wood – a combination that gladdens the heart! Pure nature, so to speak. And at the same time, incredibly attractive. Two natural materials that harmonise perfectly and seem made for each other!

Wooden wine racks are a wonderful way to store your wines in a particularly gentle and dark environment. Wood has the fantastic property of regulating air humidity while also acting as a natural insulator. Moreover, different types of wood vary in colour, grain, hardness, and weather resistance. Here you can find out more about the characteristics of different types of wood:

Which wood is best suited?

For wine racks, woods such as pine, walnut, oak, ash, and beech are often used. As long as the wine rack is placed in a location where the humidity is below 60%, the choice of wood is almost irrelevant. Oak is a particularly suitable wood, as it has properties that are especially advantageous for wine storage:

• Oak is very robust and hard.
• Oak can tolerate high humidity over the long term.
• Oak, due to its high tannin content, is practically immune to mould.
• Oak hardly warps and remains stable in shape for many years.

The only disadvantage of oak is that it is relatively expensive compared to fir or other types of wood.

Treatment for colouration

The natural appearance of wood can be very attractively altered by staining it with a natural pigment stain, allowing it to be adapted to personal preferences. Another natural and very gentle method is treatment with linseed oil, tung oil, or walnut oil. These treatments can alter both the colour and the surface of the wood. Both methods, staining and oil treatment, provide additional protection for the wood. It is important that the products used for treating wine racks are natural and solvent-free, as solvents can evaporate and penetrate the wine through the cork, which nobody wants, of course.

Laminate wood

The use of laminate wood can make particularly expensive woods like oak more affordable without having to forgo this especially beautiful and suitable type of wood. However, the bonding must be done with a wood glue of class D3 or D4 to prevent the bonding from dissolving when humidity increases.

D1 and D2 glues are not suitable for wine racks as they can only tolerate a maximum of 18% humidity, whereas wine storage rooms should have a humidity level between 45% and 65%.

In our second part on material selection for wine racks, we turn our attention to the materials metal, stone, and plastic.

Metal or Steel:

Steel is an incredibly versatile material that is very well-suited for use in wine racks. It stands out due to two key features: its very high strength and extreme durability. Another highlight is its almost unlimited malleability. Unlike wood, very little material is needed to hold the wine bottles securely. This allows for wine racks where the structure discreetly stays in the background, making the stored bottles much more visible. Metal racks impress with their simple, minimalist, and slender style. This quality is used to elegantly showcase a small number of wine bottles, allowing them to stand out in a striking manner. Especially individual bottles can be presented using a metal structure in such a way that the metal construction becomes almost invisible. The bottle appears to float – a particularly elegant eye-catcher for magnum and double magnum bottles.

Metal wine racks are protected from corrosion by a finely textured powder coating, the colour of which you can freely choose to suit your preferences. This also opens up great design possibilities, allowing for unique and special presentations.

A particularly charming combination is that of metal and wood.

Wine Racks and Wine Storage Made from Stone or Clay

Stone is a robust material, usually found in the form of fired clay, but also as limestone or tuff stone, used for wine racks or even larger wine storage areas. Stone as a material is porous, meaning it absorbs and releases humidity, which has a cooling effect in higher temperatures and a warming effect in lower temperatures. Thus, stone has a regulating influence on the room climate. Wine racks or wine storage made from stone are ideally built with mortar, so they provide long-lasting enjoyment. Wine racks made from fired clay or limestone have their own unique, particularly robust and rustic charm.

Wine Racks and Wine Storage Made from Plastic and Acrylic:

Plastic is impressive due to its lightness and the ability to be formed and coloured in virtually any way. This makes plastic an incredibly versatile material for wine storage. You can design your wine racks exactly as you wish – from practical, stackable, and very affordable wine storage boxes, to robust clay imitations made from polystyrene, to spectacular, futuristic acrylic constructions – anything is possible.