Wine Storage Guide

7 Golden Rules of Wine Storage

7 Golden Rules of Wine Storage

Temperature

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.

Cold is not a problem as long as it doesn't get so cold that ice forms. This is the case at around -7 °C, or from -10 °C for wines with a higher alcohol content. If ice forms it needs about 9% more volume than the wine - with the result that the ice pushes the cork or screw cap away and the bottle is no longer airtight. If the ice thaws again, the bottle is open and can no longer be stored. Once wine has frozen, it is best to drink it immediately after thawing, it will still be good, but will not improve.

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.



Temperature Part 2: Temperature Fluctuations

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.