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Intro
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Maybe you just found a dusty bottle of whiskey in the back of your closet. It looks about the same as the new bottle of the same bourbon you just bought, but is it? This post will discuss how whiskey changes over time, both in an opened bottle and a sealed one, and how you can maximize the shelf life of your favorite brown juice.
Does Whiskey go bad?
No, at least not in the traditional sense.
Microorganisms, primarily bacteria, fungi (molds and yeasts), and some protists, are to blame for the vast majority of what we think of as food spoilage. They latch onto sources of the nutrients they need to grow and reproduce, along the way spinning off a deluge of enzymes and waste products which can produce off odors or just plain make you sick. Molds and other fungi not only cause spoilage but can also produce mycotoxins, secondary byproducts which can have severe and acute impacts on your body and organs.
Whiskey's high alcohol content is our savior from the trials and tribulations of these microbes. It does this through two ways:
1. Disrupting Cell Membranes: Alcohol is a fantastic solvent and as such its molecules disrupt the phospholipid bilayer structure of many microorganisms cell membranes. This fatty layer normally acts as a barrier, keeping vital cell components inside and harmful substances out. When alcohol disrupts this barrier, it leaks the cell's contents, leading to cell death and therefore preventing microbial growth.
2. Dehydration: Microbes need water for their metabolic processes just like humans. At high enough concentrations (e.g. 40-60% ABV commonly found in whiskey), alcohol draws water out of microbial cells, dehydrating and killing them.
Even if some super-microbe managed to survive in the bottle, Whiskey has a very low sugar content since most of the sugars from the original grain mash are converted to alcohol during the fermentation process. Without sugar as a primary food source, microbes have a very difficult time growing and reproducing.
Bottom line, old whiskey is unlikely to make you any more sick than newly bottled whiskey.
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Why does my whiskey taste different after I open the bottle?
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While whiskey, bourbon, and scotch do not "go bad", they can degrade in flavor due to changes in their chemical compositions due to light, temperature, and oxidation.
Oxidation
The term "oxidation" can be described as a process by which any atom gains additional oxygen atom such as when carbon monoxide (CO) becomes carbon dioxide (CO2). This is typically associated with some other atom losing a bond with the oxygen atom. You may hear this referred to as an oxidation-reduction or "redox" reaction for that reason. This can happen for many organic molecules within the whiskey bottle, but is most noticeable when sulfur is oxidized into SO2 over time. I myself have noticed a sulfur note in bottles that have been open for a while, but the actual oxidative contribution to flavor change is likely quite small.
Sorry Oxidation - It's actually more of a matter of concentration
What DOES impact the flavor profile in a big way is the increase in the ratio of air to whiskey in the bottle. A very slow chemical gradient causes some of the flavoring molecules to move from the liquid into lower concentrations in the gas. This happens because the short-chain alcohols in the whiskey are both lighter and more volatile than the water in which they reside. These alcohols largely serve to concentrate other flavoring molecules such as esters due to their polarity. Esters, also often of the short-chain variety) are known for contributing fruity or floral flavors and their loss over time results in a more dull, flat, or bland whiskey. This exchange of chemicals also happens in reverse, with the relatively long chained and weighty ethanol pulling water out of the headspace of the bottle. Alcohols of the phenol group vanillin and oak lactones actually increase in flavor over time as they convert from trans to cis isomers.
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The more nuanced, expensive, and age-stated the bottle, the quicker you should probably drink it! If you opened your bottle of Pappy and realized you should have saved it, adding a little bit of argon gas (heavier than air) to the bottle can create a protective layer to stave off the chemical exchange process.
Temperature
Temperature is defined as the average kinetic energy of the molecules in a system. The more energy in the molecules; the more they move around. The more they move around; the faster this exchange of chemicals between the whiskey and the headspace occurs.
Experts recommend keeping your bottles somewhere between cellar temperature (45-65F, 7-18C) and room temperature (70F, 21C). We also note that these are the best temperatures for tasting because of human sensory reasons..jpeg "the temperature for storing your whiskey is important.")
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Light
Ultraviolet light (one of the components of sunlight) degrades the tannins, esters, and aldehydes that whiskey absorbs while spending time in oak through a process called photolysis (literally "light splitting"). UV light exists on the high-energy end of the electromagnetic spectrum. When a UV photon collides with a molecule, it transfers its energy. Since organic molecules are held together by covalent bonds (sharing of electrons between atoms), the addition of this energy may be enough to disrupt those bonds, resulting in fragmentation and rearrangement. In the context of whiskey, this disrupts the complex organic molecules responsible for its flavor profile and can create free radicals which are highly reactive due to the presence of an unpaired electron and contribute to an accelerated breakdown process.
The Wavelength/Energy Level Matters - Not all UV light is equally damaging. Higher-energy UV light (UVC with wavelengths around 200-280 nm) is the most potent for bond breaking. Thankfully, most of the UVC light from the sun is filtered out by the Earth's atmosphere, though UVB light (280-315 nm) reaches the surface and can contribute to degradation (higher wavelength = lower energy = less bond breaking).
Your indoor LED Lights are fine, they don't have anywhere near enough energy to tamper with your whiskey.
Bottom line, keep your bottle out of sunlight and away from windows. I keep mine in a happy little cabinet.
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How can I store my whiskey for optimal flavor?
Ultimately, maximizing the life of your whiskey's flavor consists of a few easy rules to minimize the impacts of those things described above:
- Don't open it until you plan on drinking it - A factory sealed bottle will likely stay good almost forever.
- Store it Out of Direct Sunlight - That mancave display is a terrible idea if it's right next to a window. Basement lair or happy dark cabinet. Sturdy shelves away from light are the best place.
- Store it Upright - While wine bottles can be stored on their sides to keep the cork wet, Whiskey has too much alcohol and will dissolve a natural cork, letting in more air and increasing the rate of flavor loss.
- Store it at Cellar or Room Temperature - Again, 65-70F is best for a variety of reasons. Keep away from heat sources like ovens, heaters, for furnaces, and don't store bottles in a hot car. The change in temperature will cause the cork to degrade more rapidly.
- Move it to a Smaller Bottle - If you do have some juice you want to preserve, put it in a smaller container. For very expensive bottles that you plan on enjoying slowly, it may even be worth putting them in single serving containers similar to those people take to whiskey swaps. This minimizes headspace and will make the flavor last longer.
General Guidance - How Fast should I consume a bottle?
Based on a review of other sites as well as my personal preferences, I would recommend:
- Unopened bottle : Less than Five years - Why do you have it if you're not going to drink it?
- Freshly opened bottle: 2 years
- Half-full bottle: 1 year
- Quarter-full bottle : 3 months
Jim Beam only guarantees their products for one year within opening for unflavored products and one MONTH for flavored options, which is right around the average for what we describe above.
A note on Vintage Bottles & Restaurants:
Jason Brauner, owner of Bourbon Bistro in Louisville, KY, notes that you should be very careful opening any bottles more than 40 years old as the cork has likely started to crumble. He also mentions that he does not like to serve whiskey from any bottles that have been open for more than six months, typically discounting or giving away those bottles as they approach the half year mark.