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Whiskey (and other spirits) Degradation and Oxidation

Hi. Does anyone have a resource or point of reference for what happens to barrel aged spirits after they are opened? I know that nothing BAD is actually going to happen to it, but I also know that there will be an evaporation of esters and alcohol alike. Most of the time, this doesn't matter much, but that bottle of Yamazaki 35, Maccallan M, or Hennessy Richard may not sell very quickly, and it damn well better taste like it was meant to when the consumer pays that kind of money. What is the time limit on this? If the bottle has been sitting on the shelf for three years because the owner is a rabid collector of status symbols, how much has the whiskey or brandy changed? 

  • Key is to look at how the spirituous product appears. Specifically, is it cloudy/milky? If so, do not serve.

    As alcohol evaporates, the product becomes more susceptible to bacterial contamination. I have seen photos of a bottle with funky islands floating in it. Avoid, obviously. And there are plenty of gradations prior to that - the milky/cloudy aspects.

    Storing at a constant temperature is important. Temperature changes act like a pump, pulling alcohol out of the bottle.

    I do not have a precise answer for the exact amount of time. Someone just yesterday asked me about an old bottle of Crown Royal, two inches left and not opened in 20 years. Cloudy. He followed my advice of discarding. Yet I have seen open bottles of Louis XIII and the like be fine for 5 years, but that was kept in a constant temperature environment.
  • Thanks. Really looking for something a little more scientific than "is it cloudy." I want to know what is happening and how to build a timeline from that.
  • Alcohol evaporates, the remaining liquid can be infected with spores/bacteria in the air. So it really depends on the environment. I image Vietnam would have a different aging window than Flagstaff.
  • Barcadi did some research on degradation leading into Tales in 2015. Honestly, what we do to care for wine is what we should do for spirits. Keep away from direct sunlight and try to avoid temperature fluctuations.

    "By exposing various glass-bottle-stored alcohols to UV radiation intended to simulate the effects of sunlight, the researchers found that over a period of 10-day exposure, bourbon lost 10 percent of its color and scotch lost 40 percent."

    Now, obviously bottles can go through oxidation based on how the bottle is stored after opening. Corks, natural and synthetic, can let in oxygen that can affect a bottle.

    There's an interesting article about oxidation that can be read here: Bottle maturation (OBE)

  • I've drank whiskey from the 1920s with crumbling corks and it was delicious. Whatever degradation happens is on the scale of decades.
  • Second that.

    Had a Johnny Red from 1937, was delicious.
    Was closed with a crown cap, so I wonder how tight the seal was.
  • I gas spirits that I rarely open.j

  • How low was the fill line? I've tasted plenty of wine with a brittle cork that was sealed just fine until the cork was disturbed and crumbled.
  • Vlada and Jacob, it's true old spirits are delicious, and JW Red was made differently decades ago and tastes different than modern versions.

    Jeremy's OP was about bottles already opened, however. not old bottles opened for the first time after decades of storing.
  • In my experience when running a high end spirits program I tend to focus on training (in order to move product) and less on wondering about the chemistry of how spirits evolve. If you're not already familiar with the science of fluid dynamics in relation to ethyl evaporation & temperature displacement then don't worry about it. If a product is on your back bar for more than 12 months then you need to review your training program. Dead Stock can kill you in the long run if you don't have the storage space; and if your staff isn't capable of making the sale then it will never move which profits you nothing. But if you want to get technical to keep up with the Hipsters (that don't know anything anyways) then here is what to look for.
    There is always a certain pressure exerted by the ethanol on the solution in the bottle (dependent on the type of enclosure used to seal the system) , called vapor pressure, which is dependent on a dynamically changing temperature environment. You can monitor the effect by adding a condenser to remove the ethanol vapor, thus creating a much more complex, dynamic system (do you really want to do this for every single bottle behind your bar?). The simplest way to determine the rate of evaporation would be to measure the amount of ethanol extracted at various time & Temperature intervals and plot these against a timetable. The rate would be the slope of the plotted line (which probably will not be constant, since as the amount of ethanol decreases from the original solution, it will slow the rate of collection.)...
    For me it all comes down to how you manage your program and understanding your guests, we've all had the owners that want grand products on a list just for the sake of having them. The best advice I can give is to treat your high end spirits, beer & Nihonshu just like wine. Minimize their exposure to light, temperature & oxygen. And train your staff to give them the tools needed to successfully sell. To make it fun go to Tales of the Cocktail, there you can find a myriad of resources & drinking buddies. Cheers!