February 8th will be the second International Scotch Day and we've been looking into the Old Bottle Effect.

The Old Bottle Effect is the changing of a whisky's flavor over time. This is also true of wine and the primary cause is thought to be oxidization, or in other words the reaction of the liquid with oxygen. In wine and whisky, oxygen is slowly released through the cork over time. For wine this can actually be desired as it tends to change wines from fruity flavors to nuttier flavors but only with small amounts of oxygen released over time. For wines where a fruity flavor is desired, bottlers will seal instead of use a cork to ensure that flavor is not lost.

However, too much oxygen will spoil both whisky and wine, hence why both are corked in most instances. In wine bottling, nitrogen is used to displace oxygen to stop the product spoiling. Nitrogen is an inert gas so will not react and change the flavor of the wine. For this purpose, nitrogen will either be provided by a nitrogen gas generator or from nitrogen cylinders.

For whisky there are two major considerations to distinguish the true nature of the Old Bottle Effect, first is the alcohol content. Oxygen will affect whisky flavors less than that of wine due to the higher alcohol content. In whisky bottles, any oxygen will be used up by the alcohol vapors meaning less can react with the liquid. The other major consideration to determine the existence of Old Bottle Effect are the methods of distillation. Because distillation methods have modernized over the past few decades and different whiskies are distilled in different ways, there is a likelihood that these are having an impact on the flavors of whisky whilst in the bottle.

There is still little understanding of precisely what causes the Old Bottle Effect - and if there is one at all, particularly when it comes to whisky. To have any chance of protecting these products from oxidization, nitrogen, supplied by a nitrogen gas generator, is the best solution.

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Sources:

https://scotchwhisky.com/magazine/ask-the-professor/16942/does-whisky-change-in-an-unopened-bottle/

https://scotchwhisky.com/magazine/latest-news/17437/international-scotch-day-2018-announced/