On caravans, ships, temperatures and wine…

A winemaker once told me how he sold quite a lot of wine to a father whose daughter was to be married in a few months’ time. After the wedding the enraged father told the winemaker that the wines were not the same as when he bought it and tasted awful at the wedding. Turns out he left the wine over the summer holidays in his caravan in the sun before the wedding…

How one stores wines is of critical importance if it is not consumed in a short period of time. Of the external factors influencing how a wine mature temperature is the most important. One can buy the most expensive wine, but storing it on your ceiling will turn it into something akin to a liquid that should rather go into your car’s engine. The wine maker can control the wine’s temperature to some extend during the production process, but has little control over it once the wine left the cellar’s premises and stored in a bottle.

One period where wine is often exposed to too high temperatures is during the transport process, especially when it is send overseas with a ship. Temperature loggers have been placed with wine during the shipping process and interesting enough the highest temperatures were recorded when the wines were standing in shipping containers in the harbour. When summer temperatures are say around 35 °C in the sun in Cape Town, temperatures in the container can easily go up to 45-50 °C if no air conditioning is employed.

It is also believed that variable temperatures are also not good for a wine’s quality. This has however, not been scientifically tested and we thus set out to test this theory a few years ago. We took a delicate Chenin blanc wine that has been recently bottled with a screw cap as well as a one year old Sauvignon blanc wine (closed with a cork). Both these wines were then exposed to constant temperatures at 37, 15 and -4 °C as well as variable temperatures for a 46 day period (roughly the shipping time from SA to the UK). The latter treatment’s temperatures were very variable, almost like cabinet positions under our previous president. In this treatment the wine were left at 30°C for eight hours per day, then at 37°C for eight hours and finally at 20°C for eight hours per day for the first week, which was supposed to simulate morning, afternoon and night-time temperatures in the harbour in summer. It was then left at a constant temperature of 15°C for 30 days, simulating the temperature on the ship. It was then finally exposed to -4°C, 4°C and 8°C for eight hours per day for the last week of the trial, which was supposed to simulate night, morning and afternoon temperatures in winter time in the UK. The average temperature over the 46 day trial period was similar between those wines exposed to a constant 15°C and to variable temperatures (average of 15.3°C).

Ship 2

We then asked a trained sensory panel to taste the wines in a blind manner after this 46 day period. The wines left at a constant 37°C were much higher in negative over aged aromas, vegetative aromas and a burning sensation on the palate. The tropical aromas in this wine were also much lower than in the other wines. The wine left at a constant -4 °C were much higher in tropical aromas and lower in the above-mentioned negative aromas and tastes. Those left at a constant 15°C were slightly higher in the negative aromas and slightly lower in the positive tropical aromas compared to those left at the constant -4 °C. However, interesting enough the panel could basically not pick up any differences between the wines left at a constant 15 °C and those left at the variable temperatures. This is due to the fact that the average temperatures of these two treatments were the same.

This basically means that if you store a wine between say 4 and 14 °C (a 10°C difference) it will still mature slower than the same wine left between 20 and 22 °C for example (only a 2 °C difference). The average temperature you stored you wine at is thus more important than some temperature variations. However, in a caravan a wine probably needs to be consumed the same day, this will help to contribute to a long and happy marriage!

Reference:

WJ du Toit and C. Piquet. (2014). Research note: Effect of simulated shipping temperatures on the sensory composition of South African Chenin and Sauvignon blanc wines. South African Journal of Enology and Viticulture. 35, 278-282

 

 

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