For tiden svømmer de digitale medier over med reklamer for en ny og elegant vinkøler, hvor man nedsænker en kraftigt nedkølet stålcylinder fyldt med kølevæske direkte i vinflasken. Dette fryseelement på minus 18 grader formodes så at køle vinen, så man hurtigt kan skænke op i glasset via den medfølgende hældetud. Det lyder forjættende, og jeg lod mig da også lokke af de højtråbende reklamer til at prøve vidunderet. Her er så mine oplevelser – på godt og ondt – med at bruge denne alternative afkølingsmetode.
Jagten på den rette vintemperatur
En vins temperatur er en af de mest afgørende faktorer, når vinnydelsen skal optimeres. Samtidig er den rette temperatur forudsætningen for, at vin og vinmager ydes fuld retfærdighed ved en kvalitetsbedømmelse. Gennem tiderne har der været utallige lærde og heftige diskussioner om, hvad den rette temperatur er for en given vin, men ét står fast: Der er så godt som altid nødvendigt at afkøle vinen, før den præsenterer sig bedst muligt.
Men hvad er den nemmeste og den hurtigste og den sikreste måde at afkøle en vin på? Det vil denne artikel komme med et bud på.
De to situationer
Der er lige den krølle på kølebehovet, at det eksisterer i to vidt forskellige versioner: For det første kan der være brug for at køle en rigeligt varm vin ned til dens formodede optimale drikke-temperatur, før flasken serveres. Situation to opstår efterfølgende, når proppen er kommet af: Hvordan fastholdes den optimale temperatur under hele serveringen? Den varme stueluft bevirker – ikke mindst for hvidvin – at det sidste glas i flasken ofte bliver lunkent og kedeligt.
Derfor afprøvede jeg kølestaven i begge situationer og satte dens præstationer op mod tre af de vanlige metoder til nedkøling af vin. Nemlig: Et almindeligt køleskab og en vinkølebeholder fyldt med isvand og endelig blev der brugt en dybfryserkold kølemanchet, der omsluttede det meste af flasken.
Den hurtigste vej til målet
Udgangspunktet for dette forsøg var fire farvede Alsace-helflasker, der var påfyldt 6 deciliter vand ved stuetemperatur. Hvert 15. minut blev de fire flasker rystet for at udelukke de værste af flaskens indre temperaturforskelle, før målingen blev foretaget med brug af et infrarødt termometer.
Målet var her at få vinens temperatur ned på cirka 10 grader, hvad der ofte er en fornuftig temperatur for en hvidvin. Lufttemperaturen var ved start 23.5 grader. Resultaterne fremgår af skema 1.
Forsøg 2: En konstant vintemperatur
Fire farvede Alsace-helflasker blev påfyldt seks deciliter vand, der var afkølet til cirka 10 grader. Hvert 15. minut blev de fire flasker rystet for at forebygge de værste temperaturforskelle mellem top og bund. Målingerne blev også her foretaget med et infrarødt termometer.
Forsøget gik ud på at holde vinens starttemperatur over længst mulig tid og med en variation på mellem plus og minus to grader i den åbne flaske. Køleskabsvinen blev opbevaret i køleskab mellem hver enkelt måling, mens de øvrige flasker blot stod på bordet ved stuetemperaturen på 23.5 grader. Resultaterne fremgår af skema 2:
Plusser og minusser ved den hidtidige kølemetoder
Det gode gamle køleskab fungerer glimrende til afkøling, blot man har tid nok, da det let kan tage to timer eller mere at få en stuelunken hvidvin ned på et acceptabelt drikkeniveau. Et ægte vinkøleskab fungerer takken bedre, da man her kan indstille temperaturen, præcis som den ønskes. Men igen kræves der tålmodighed, hvis en varm flaske skal seriøst ned i temperatur. Det almindelige køleskab fungerer derimod fint, når den afkølede vins temperatur blot skal være stabil. Men i praksis er det besværligt, da flasken skal ind ud af køleskabet, når der skal skænkes op igen.
Vinkølespanden med en blanding af is og vand er klart den hurtigste og mest effektive metode til at køle en lunken vin ned, da det typisk tager 15-20 minutter. Den kraftige køleeffekt kan også være problematisk, hvis man blot skal vedligeholde temperaturen, da selv en hvidvin hurtigt kan blive alt for kold. Det kan man dog kompensere for ved at fjerne en del af isen, når den rette temperatur er nået.
Før vinkøleren fungerer optimalt, skal man sikre sig, at der ikke blot er is, men også vand i spanden, da varmeledningen har ringe arbejdsvilkår ved ren is og intet vand. Især på restauranter begås denne fejl ofte, så tøv ikke med at bede om vand i din isspand her.
Ønsker man en særlig hurtig afkøling, kan isvandet tilsættes en håndfuld almindeligt salt. Herved opnår man en frysepunktsænkning, så is-vand-blandingen bliver koldere end de nul grader, som væsken normalt holder, så længe der fortsat er is i vandet. Ved tilsætning af 10 vægtprocent salt, kan man komme ned under de seks minusgrader.
Den tredje og sidste metode er kølemanchetten, der dybest er et vanligt kølement, der er skræddersyet, så det kan omslutte det meste af en vinflaske – nærmest som en art handske. Forsøgstallene viser, at manchetten er dårligt egnet til at sænke temperaturen på en lunken vin mere end cirka 6 grader, men til gengæld sker det i løbet af cirka et kvarter. Er vinen derimod nedkølet ved serveringen, fungerer manchetten glimrende i mere end en time. Vær dog opmærksom på, at manchetten ofte vil være for kraftig en kuldemedicin for flere typer rødvin – eksempelvis ældre vine – der typisk skal serveres omkring de 18 grader.
Kølestaven er ingen tryllestav
Kølestaven har seriøse problemer med at leve op til annoncernes gyldne løfter. Staven formår kun at sænke en lunken vins temperatur med noget, der ligner tre grader i løbet af en halv time. Dens køleelement er ganske enkelt underdimensioneret så markant, at det rent fysisk ikke rummer den fornødne kulde-kapacitet til at håndtere en flaske lunken vin.
Eksempelvis kræves der rent fysisk cirka 33 Kilojoule at sænke temperaturen fra 23 grader til 10 grader i en flaske vin. Kølelementet vejer cirka 81 gram og har en anslået varmefylde på 2.8 Kilojoule pr Kilo pr °C, hvad der ved en nedkøling til minus 18 grader giver en total kølekapacitet på cirka 6 Kilojoule. Det betyder blandt andet, at vægten af kølelementer cirka skal femdobles, før frysestaven kan klare nedkølingsjobbet og nå de 10 grader. Se mere om fysikken bag nedkølingsprocessen i faktaboksen om køleelementets opbygning.
Derfor er stavkøleren reelt ude af stand til at køle selv en rødvin passende ned, hvis vinen har noget der ligner en vanlig stuetemperatur. Det ser dog marginalt bedre ud, når det gælder om at fastholde temperaturen på en i forvejen afkølet vin. Her kan staven holde de 10 grader i noget, der ligner 15 til 20 minutter. Herefter overmander fysikkens love annoncørernes anprisninger inden om, hvorfor der efterfølgende sker en markant temperaturstigning i den afkølede vin.
På plussiden skal det dog anføres, at apparat er smukt designet, og funktionaliteten ved opskænkningen er i top. Der findes tilsyneladende utallige forskellige versioner og brands af vidunderet i de danske netbutikker, men ved en visuel inspektion ligner de hinanden til forveksling. I hvert fald bruger de alle det samme køleprincip og har dermed de samme begrænsninger. Vær også opmærksom på solide prisforskelle, hvis du skulle have lyst til selv at testkøre vidunderet.
Ud fra disse målinger er det mit gæt, at udvikler-firmaets marketingafdelingen i farten har glemt at lade produktudviklerne foretage de mest basale termodynamiske beregninger på ”opfindelsen”. I stedet er man blot begyndt at sælge denne dysfunktionelle vinkøler og love guld og grønne skove og dermed lokke husarerne ind – inklusive undertegnede – i folden.
Der er med andre ord intet belæg for anprisningerne og løfterne i annoncerne. Og slet ikke for billederne, der viser et vindrikkende selskab, hvor alle rundt om bordet smiler frydefuldt, mens vinglassene dugger…
Et vintip til iværksættere
Den perfekte metode til at styre vinens temperatur – både ved afkøling og ved længerevarende servering – findes altså ikke – endnu. En skønne dag kommer der forhåbentligt et veldesignet nyt elektronisk apparat, hvor man kan sætte en given temperaturgrænse på vinkøleren, så en termostatordning kunne sørge for både køling og opvarmning.
Denne opgave er jo ikke ligefrem rocket-science, og opfindelsen vil ramme et ganske stort internationalt og hidtil udækket marked – inklusive undertegnede. Blot skal prisen være nogenlunde rimelig, og designet skal være smagfuldt, og funktionaliteten skal nødvendigvis være i top – ikke mindst når det gælder kapacitet og hurtighed.
Idéen er hermed givet videre til kreative igangsættere blandt læserne. Der findes i dag termostatstyrede kaffekrus, der holder kaffen varm, så længe det skal være. Desværre er de dog ganske kostbare på trods af den enkle konstruktion.
Fakta om Kølestaven
Kølestaven består af et plastik-mellemstykke med en hældetud og et påskruet cylinderformet metal-køleelement
Køle-cylinderen er 19 centimeter langt og har den diameter på 1.6 cm
Cylinderen er udført i stål og forsynet med en kerne af et flydende kølemiddel
Sandsynligvis er kølemidlet glycerol, som i vanlige fryseelementer
Kølecylinderens massefylde er 2.1 gram pr kubikcentimeter
Kølecylinderens anslåede varmefylde er 2.8 Kilojoule pr Kilo pr °C
Kølecylinderen vejer 81 gram og har et volumen på 38 kubikcentimeter
Derfor skal man fjerne cirka en halv deciliter vin, inden kølelementet sættes ned i flasken
I modsat fald flyder vinen ud over kanten af flasken
Chablis – Termodynamisk trylleri i vinmarken
I Chablis-området har man ofte problemer med nattefrost om foråret, hvor vinstokkens nyudsprungne løv er særligt sårbart. En udbredt praksis er at sprøjte forstøvet vand ud over marken, så løvet efterfølgende dækkes af et tyndt lag is på grund af luftens og himlens frostgrader.
Dette kan umiddelbart synes at være en rigtig dårlig idé, da bladenes isdække burde skade det spæde løv. Men takket været en termodynamisk spidsfindighed, så har denne metode gennem tiderne sikret os adskillige flasker Chablis, som vi ellers ville være gået glip af.
Forklaringen ligger gemt i det fysiske begreb ”Faseskifte”. Termen faseskifte dækker over, at når en væske fryser til is – og dermed går over i en fast fase – så frigives der energi. Der sker med andre ord en form for opvarmning. Det modsatte er også tilfældet: Når eksempelvis en isterning tør op og bliver til flydende vand, så bindes der energi. Her sker der så en afkøling. Dette er en af flere årsager til, at en vinkøler fyldt med is og vand er så effektivt et værktøj til afkøling af vin.
I Chablis bliver det forstøvede vand til is, når nattefrosten er særlig kraftig. Det frigiver så meget varme, at bladene overlever, selv om de dækkes af et tyndt lag is, da løvet normalt tåler et sted mellem en og to minusgrader. Oven i købet så isolerer is-laget mod frosten i natteluften og modvirker udstråling mod den meget kolde nattehimmel.
Naturlove og vinkølere
Når man vil afkøle en vin – og dermed flytte energi fra ét sted til et andet – er der ganske mange naturlove i spil. Her er så nogle få af de vigtigste.
Varmeledning:
Her flyttes der energi fra ét punkt til et andet ved fysisk kontakt. Eksempel: Når den ene ende af en metalstang bliver varm, begynder molekylerne at vibrere mere. De aktiverede molekyler skubber så til nabomolekylerne, som derfor også begynder at vibrere hurtigere, så de opvarmes. Og sådan fortsætter det, indtil varmen har spredt sig jævnt gennem hele stangen. Og modsat: Når et køleelement er i kontakt med en vin, så mindsker det molekylebevægelserne i vinen, så vinens temperatur falder – og køleelementets temperatur stiger tilsvarende. Energi forgår aldrig.
Varmefylde:
Varmefylden er et mål for, hvor meget varmeenergi der skal til for at opvarme 1 kilogram af et stof med 1 grad. Eksempelvis har vand en høj varmefylde, så det tager lang tid at bringe en gryde vand i kog. Metal har derimod en lav varmefylde, så en metalgryde bliver hurtigt varm. Vands – og dermed vins – varmefylde – er på cirka 4.2 Kilojoule pr Kilo pr °C.
Konvektion:
Konvektion overfører varme i væsker eller luftarter, når disse er i bevægelse. Bevægelsen bevirker, at der transporteres energi fra ét punkt til et andet. Princippet bruges blandt andet i konvektionsovne, hvor et temperaturvalg med konvektion på måske 200 grader, svarer til cirka 180 grader uden brug af konvektion.
Faseskifte:
Når et stof skifter fra at være en væske og går over til at være på fast form – eller modsat går fra fast til at være flydende – så ændres stoffets indre energi. Et faseskifte kan både opvarme og afkøle – afhængig af faseskiftets retning. Det er dette energitrylleri ved faseskifte-processen, der muliggør, at et køleskab kan fungere. I køleskabet eksporterer et kompressordrevet faseskifte energi til omgivelserne, så køleskabets inderside bliver koldere – og omgivelserne opvarmes tilsvarende. Se mere om faseskifte i faktaboksen om Chablis.
Here follow the article in English
Cool It – the art of chilling a bottle of wine
By NIELS EHLER
At the moment, digital media is awash with adverts for a new and elegant wine cooler, where you immerse a heavily chilled steel cylinder filled with coolant directly into the wine bottle. This cooling element, set to minus 18 degrees, is supposed to chill the wine so that you can quickly pour it into a glass via the included spout. It sounds promising, and I was certainly tempted by the high-profile adverts to try out this marvel. So here are my experiences – for better or worse – of using this alternative cooling method.
The quest for the right wine temperature
A wine’s temperature is one of the most crucial factors when it comes to optimising the wine-drinking experience. At the same time, the right temperature is essential for doing full justice to both the wine and the winemaker when assessing its quality. Throughout history, there have been countless scholarly and heated discussions about what the right temperature is for a given wine, but one thing is certain: it is almost always necessary to chill the wine before it can be enjoyed at its very best. But what is the easiest, quickest and safest way to chill a wine? This article will offer some suggestions.
The two scenarios
There is just one catch when it comes to the need for chilling: it comes in two very different forms. Firstly, it may be necessary to chill a wine that is considerably too warm down to its presumed optimal drinking temperature before the bottle is served. Situation two arises afterwards, once the cork has been removed: how do you maintain the optimal temperature throughout the serving? The warm air in the room means – particularly for white wine – that the last glass from the bottle often ends up lukewarm and dull.
I therefore tested the cooling stick in both situations and compared its performance with three of the usual methods for chilling wine. Namely: a standard fridge, a wine cooler filled with ice water, and, finally, a freezer-cold cooling sleeve that wrapped around most of the bottle.
The quickest way to the result
The starting point for this experiment was four coloured full-sized Alsace bottles, each filled with 6 decilitres of water at room temperature. Every 15 minutes, the four bottles were shaken to even out the most significant temperature variations within the bottles before measurements were taken using an infrared thermometer.
The aim here was to bring the wine’s temperature down to around 10 degrees, which is often a sensible temperature for a white wine. The ambient temperature at the start was 23.5 degrees. The results are shown in Table 1.
Experiment 2: A constant wine temperature
Four coloured full-sized bottles of Alsace wine were filled with six decilitres of water, which had been cooled to approximately 10 degrees. Every 15 minutes, the four bottles were shaken to prevent significant temperature differences between the top and bottom. Here too, the measurements were taken using an infrared thermometer.
The aim of the experiment was to maintain the wine’s initial temperature for as long as possible, with a variation of between plus and minus two degrees in the open bottle. The fridge wine was stored in the fridge between each measurement, whilst the other bottles were simply left on the table at room temperature (23.5 degrees). The results are shown in Table 2:
Pros and cons of the cooling methods used to date
The good old fridge works brilliantly for cooling, provided you have enough time, as it can easily take two hours or more to bring room-temperature white wine down to an acceptable drinking temperature. A proper wine fridge works much better, as you can set the temperature exactly as you wish. But again, patience is required if a warm bottle needs to be cooled down significantly. A standard fridge, on the other hand, works fine when the temperature of the chilled wine simply needs to remain stable. In practice, however, this is inconvenient, as the bottle has to be taken in and out of the fridge every time you want to pour another glass.
A wine-cooling bucket filled with a mixture of ice and water is clearly the quickest and most effective method for cooling down a lukewarm wine, as it typically takes 15–20 minutes. The powerful cooling effect can also be problematic if you simply need to maintain the temperature, as even a white wine can quickly become far too cold. However, you can compensate for this by removing some of the ice once the correct temperature has been reached.
Before the wine cooler works optimally, you must ensure that there is not only ice but also water in the bucket, as heat transfer is poor with pure ice and no water. This mistake is often made, particularly in restaurants, so do not hesitate to ask for water in your ice bucket there.
If you want the wine to chill particularly quickly, you can add a handful of ordinary salt to the ice water. This lowers the freezing point, so the ice-water mixture becomes colder than the zero degrees that the liquid normally maintains, as long as there is still ice in the water. By adding 10 per cent by weight of salt, you can get the temperature down below minus six degrees.
The third and final method is the cooling sleeve, which is essentially a standard cooling sleeve that has been tailored to fit snugly around most of a wine bottle – much like a glove. Test results show that the sleeve is poorly suited to lowering the temperature of a lukewarm wine by more than approximately 6 degrees, but this does happen within about a quarter of an hour. If, on the other hand, the wine is already chilled when served, the sleeve works brilliantly for more than an hour. Bear in mind, however, that the sleeve will often be too powerful a cooling agent for several types of red wine – such as older wines – which are typically served at around 18 degrees.
The cooling stick is no magic wand
The wine cooler has serious problems living up to the golden promises made in the adverts. It only manages to lower the temperature of a lukewarm bottle of wine by something like three degrees in half an hour. Its cooling element is quite simply so significantly undersized that it physically lacks the necessary cooling capacity to handle a bottle of lukewarm wine.
For example, it takes approximately 33 kilojoules to lower the temperature from 23 degrees to 10 degrees in a bottle of wine. The cooling element weighs approximately 81 grams and has an estimated specific heat capacity of 2.8 kilojoules per kilogram per °C, which, when cooled to minus 18 degrees, gives a total cooling capacity of approximately 6 kilojoules. This means, amongst other things, that the weight of the cooling elements would need to be increased approximately fivefold before the cooling stick could handle the cooling task and reach 10 degrees. Find out more about the physics behind the cooling process in the fact box on the structure of the cooling element.
Consequently, the wine chiller is effectively incapable of cooling even a red wine to a suitable temperature if the wine is at anything resembling normal room temperature. However, it performs marginally better when it comes to maintaining the temperature of wine that has already been chilled. In this case, the chiller can maintain 10 degrees for around 15 to 20 minutes. After that, the laws of physics get the better of the advertisers’ claims, which is why there is subsequently a marked rise in the temperature of the chilled wine.
On the plus side, however, it should be noted that the device is beautifully designed, and its functionality when serving wine is top-notch. There appear to be countless different versions and brands of this marvel in Danish online shops, but on visual inspection they look almost identical. In any case, they all use the same cooling principle and therefore have the same limitations. You should also be aware of significant price differences if you fancy giving this marvel a go yourself.
Based on these measurements, my guess is that the developer company’s marketing department, in the rush, forgot to let the product developers carry out the most basic thermodynamic calculations on the ‘invention’. Instead, they’ve simply started selling this dysfunctional wine cooler, promising the moon and the stars, and thereby luring the gullible – including yours truly – into the fold.
In other words, there is no basis whatsoever for the claims and promises made in the adverts. And certainly not for the pictures showing a group of people drinking wine, with everyone around the table smiling joyfully whilst their wine glasses are covered in condensation…
A wine tip for entrepreneurs
The perfect method for controlling the temperature of wine – both when chilling it and during prolonged serving – does not, therefore, exist – yet. One fine day, hopefully, a well-designed new electronic device will come along, allowing you to set a specific temperature limit on the wine cooler, so that a thermostat system can handle both cooling and heating.
This task is, after all, not exactly rocket science, and the invention would tap into a fairly large international and as yet untapped market – including yours truly. The price simply needs to be reasonably affordable, the design tasteful, and the functionality must be top-notch – not least when it comes to capacity and speed.
The idea is hereby passed on to creative entrepreneurs amongst our readers. Thermostat-controlled coffee mugs are already available today that keep coffee hot for as long as required. Unfortunately, however, they are quite expensive despite their simple design.
Facts about the Cooling Rod
The Cooling Rod consists of a plastic connector with a spout and a screw-on cylindrical metal cooling element
The cooling cylinder is 19 centimetres long and has a diameter of 1.6 cm
The cylinder is made of steel and contains a core of liquid coolant
The coolant is likely to be glycerol, as in standard ice packs
The density of the cooling cylinder is 2.1 grams per cubic centimetre
Estimated specific heat capacity of the cooling cylinder is 2.8 kilojoules per kilogram per °C
The cooling cylinder weighs 81 grams and has a volume of 38 cubic centimetres
Therefore, you must remove approximately half a decilitre of wine before placing the cooling element into the bottle
Otherwise, the wine will spill over the rim of the bottle
Chablis – Thermodynamic magic in the vineyard
In the Chablis region, night-time frosts are a frequent problem in spring, when the vines’ newly sprouted foliage is particularly vulnerable. A common practice is to spray atomised water over the vineyard, so that the foliage is subsequently covered by a thin layer of ice due to the freezing temperatures in the air and the sky.
At first glance, this might seem like a very bad idea, as the layer of ice on the leaves should damage the tender foliage. But thanks to a thermodynamic quirk, this method has, over the years, ensured that we have been able to enjoy numerous bottles of Chablis that we would otherwise have missed out on.
The explanation lies in the physical concept of ‘phase change’. The term ‘phase change’ refers to the fact that when a liquid freezes into ice – and thus changes to a solid state – energy is released. In other words, a form of heating takes place. The opposite is also true: when, for example, an ice cube melts and turns into liquid water, energy is absorbed. This results in cooling. This is one of several reasons why a wine cooler filled with ice and water is such an effective tool for chilling wine.
In Chablis, the atomised water turns to ice when the night frost is particularly severe. This releases so much heat that the leaves survive, even though they are covered by a thin layer of ice, as leaves can normally withstand temperatures of between minus one and minus two degrees. What’s more, the layer of ice insulates against the frost in the night air and prevents heat from escaping into the very cold night sky.
The laws of nature and wine coolers
When you want to chill a bottle of wine – and thereby transfer energy from one place to another – there are quite a few laws of nature at play. Here are a few of the most important ones.
Thermal conduction:
Here, energy is transferred from one point to another through physical contact. Example: When one end of a metal rod becomes hot, the molecules begin to vibrate more rapidly. The activated molecules then push the neighbouring molecules, which consequently also begin to vibrate faster, causing them to heat up. And so it continues until the heat has spread evenly throughout the entire rod. Conversely, when a cooling element is in contact with wine, it reduces the molecular motion in the wine, causing the wine’s temperature to fall – whilst the cooling element’s temperature rises accordingly. Energy is never lost.
Specific heat capacity:
Specific heat capacity is a measure of how much heat energy is required to raise the temperature of 1 kilogram of a substance by 1 degree. For example, water has a high specific heat capacity, so it takes a long time to bring a pan of water to the boil. Metal, on the other hand, has a low specific heat capacity, so a metal pan heats up quickly. The specific heat capacity of water – and therefore of wine – is approximately 4.2 kilojoules per kilogram per °C.
Convection:
Convection transfers heat in liquids or gases when they are in motion. The movement causes energy to be transported from one point to another. This principle is used, for example, in convection ovens, where a convection setting of, say, 200 degrees corresponds to approximately 180 degrees without the use of convection.
Phase change:
When a substance changes from a liquid to a solid – or, conversely, from a solid to a liquid – its internal energy changes. A phase change can cause both heating and cooling, depending on the direction of the phase change. It is this energy transformation during the phase change process that enables a fridge to function. Inside the fridge, a compressor-driven phase change transfers energy to the surroundings, so that the inside of the fridge becomes colder – and the surroundings are heated accordingly. Find out more about phase change in the fact box on Chablis.