Open Bottle Storage: Headspace

Open Bottle Storage: Headspace

From Left to Right: 4 oz bottle filled with 4 oz of whisky. 4 oz bottle filled with 3 oz of whisky. 4 oz bottle filled with 2 oz of whisky. 4 oz bottle filled with 1 oz of whisky.

 

We wanted to see how different levels of headspace would affect whisky over time. We took 4 oz amber glass boston round bottles and then filled them with four different amounts of whisky: 4 oz, 3 oz, 2 oz, 1 oz. After that we vacuum sealed the bottles and kept them in a dark temperature controlled environment to eliminate other variables.

Another test we wanted to run was how a half filled regular 750 ml bottle of whisky would change over the course of a year. This was to test the idea that you do not need to do anything to preserve a bottle of whisky until you finish half the bottle because whisky is pretty stable but will oxidize given enough headspace and time. We took a 750 ml bottle filled with 325 ml of whisky and kept it in a dark temperature controlled environment to eliminate other variables.


A Year Later

NOTE: When we speak about the differences in taste or score, it is the difference between a specimen and the control, and another specimen and the control. Not the direct difference between the two specimens.

There was a clear relationship between headspace and the change in taste of a whisky. In 3 of the 4 specimens it shows a clear decrease in change that correlates with a decrease in headspace. Because there were no other variables in play we conclude that this correlation is in fact causation. There were identical amounts of surface area exposed to the headspace in ¾ of the specimens. They were stored identically and there are no other possible factors in play that were not eliminated or identical. There was a slight abnormality however in the 4 oz bottle with a 2 oz fill. We do not know definitively why this happened, but we believe there was indeed a greater change in taste but it was not reported. Our guess is that the larger change made the whisky taste better so it was not reported accurately. Another possibility is that vacuum sealing had done something to change that bottling more than the other bottles.

The average scores of each set of specimens. (Lower is better.)
Specimen Description Total Average Nose Average Palate Average Finish Average
4 oz bottle, 4 oz fill, cool dark place, vacuum seal 1.56 0.94 2 1.75
4 oz bottle, 3 oz fill, cool dark place, vacuum seal 2.08 1.5 2.25 2.5
4 oz bottle, 2 oz fill, cool dark place, vacuum seal 1.75 1.13 2.13 2
4 oz bottle, 1 oz fill, cool dark place, vacuum seal 4.54 3.75 5.75 4.13

 

Even if we were to throw out these results entirely other results throughout this study show similar results. For example, a 750 ml bottle filled with 325 ml of whisky scored an average of 1.13 points compared to a 750 ml bottle filled with 150 ml of whisky scored an average of 1.96 points. That is -0.83 points worse for the bottle that had more headspace which supports our theory.

Another example of less headspace creating less change in a bottle of whisky. The average scores of each set of specimens. (Lower is better.)
Specimen Description Total Average Nose Average Palate Average Finish Average
750ml bottle, 325ml fill, cool dark place 1.13 1.25 1.25 0.88
750ml bottle, 150ml fill, cool dark place 1.96 2 2.13 1.75

The myth that you do not need to do anything to whisky until the bottle is half empty has been proven mostly wrong, but sort of correct. A half empty bottle of whisky will maintain its taste incredibly well has been proven correct as long as it was kept upright, in a dark temperature controlled environment and with a good cork. However, that whisky has degraded each time the bottle was opened to take a pour in order to get to the half empty point. In this case the myth held true since it was a 750 ml bottle of whisky that was opened and then immediately had half of it emptied and the rest was stored in a dark temperature controlled environment with a cork in excellent condition. However, that is not how most bottles of whisky are consumed so we cannot say the myth is true. Most bottles of whisky are opened many times over the course of several months which more closely resembles a 750 ml bottle that has 1 oz poured out every month over the course of a year. The difference is not huge, but is it higher. This leaves us with a significant modification to the myth to create a truth: If you plan to finish a bottle of whisky in under a month you do not need to do anything beyond storing the bottle of whisky upright in a dark temperature controlled environment with a cork that is in excellent condition.

The average scores of each set of specimens. (Lower is better.)
Specimen Description Total Average Nose Average Palate Average Finish Average
750ml bottle, 325ml fill, cool dark place 1.13 1.25 1.25 0.88
750ml bottle, 1 oz pours/month, cool dark place 1.92 1 2.25 2.5