Not all the bottles are created equal, brown bottles are much better than green, with clear being the worst at filtering out UV light. Bodnar says that all types of glass bottles can eventually let in enough light to create the dreaded "skunky" character in a beer, which happens when isohumulones, hop-derived molecules, are compromised and parts of these molecules bind with sulfur atoms (which is actually very similar to the chemical make-up of a skunk's natural defense mechanism). Cans, on the other hand, are completely impervious to light.

Another enemy of beer, oxygen, can also get into bottles from under the cap or cork and that can react with the beer, creating a stale, cardboard character.

“I often perceive this as a dull, old flavour, which is unfortunately common enough in some bottled imported beer that simply has travelled too long to get to our market,” says Bodnar.

There are exceptions. Some styles of beer benefit from the slow oxidation in the bottle and get better age. Very complex and high-alcohol beers, such as imperial stouts, barley wines and big Belgian Abbey ales, will actually taste amazing after a few years.

“The slight oxidation imparts a sherry-like character which adds complexity and is quite delicious. I actually have nearly 100 bottles of various styles suitable for aging in my cellar currently, some over five years old,” says Bodnar.