What's with Hops and Aging?

This is a topic that causes a lot of confusion, and understandably so.

The question usually comes from people who are just getting into craft beer, enough that they have tried various styles, and have done some reading about the history of beer, brewing, and various ingredients.

"If hops are a preservative, why do people say it's best to drink IPAs and other hoppy beers fresh?"

Well, here's where it's important to separate the way hops got into beer from the reason that we use them today.

Hops were originally used as a preservative in beer.  This was before pasteurization and refrigeration, and especially refrigerated transportation and storage, were a thing.  Hops kept harmful bacteria out of our ancestors' beer, which is the origin of their use in beer.

The safety of beer, however, no longer depends on hops.  We now have pasteurization, effective packaging, and refrigeration from the brewery right through the consumer. So while it is true that beer was originally hopped for preservation, this is no longer the case.  Yes, it's even true that some popular styles of beer we drink today have their origins (in a loose, rough, kind of way) in beers that were intended to have an incredibly long shelf life while traveling through various climates.

That being said, many beers, and in particular those styles originally intended for long life and travel (IPAs), are now hopped more for flavor and aroma than anything else.  In fact, there are hops bred and engineered to emphasize particular flavors.  Individual flavors from hops, like any other flower, don't hold up particularly well with age.  They don't go bad, per se, they just don't fade.

So the reality of it is, if you were to open two beers, the same in every way, but one hoppier than another, and leave them out for a week, the hoppier beer might be "better," "safer" or "fresher" than the unhopped beer in a scientific way.  It is less likely to be affected by harmful bacteria, or to make you sick.  On the other hand, while it hasn't necessarily gone bad, it is unlikely to have the same citrus, pine, resin (think marijuana), or grassy notes that it had when it was fresh.

The same principal goes for aging beers still in their containers.  Hoppy beers don't go "bad," and in fact, are probably less likely to do so than some of the beers we age (in barrels or in bottles) more frequently, but they also aren't as great.  In fact, since many of the beers we age are more malt (sugar) focused, brewers generally have to make sure they have a significant alcohol content, and are also constantly testing barrel aged beers for the presence of harmful bacteria.  You probably wouldn't have to be as vigilant if barrel aging an imperial IPA.  On the other hand, the very fresh, floral, piney, grassy, skunky, or other flavors that make people go nuts for IPAs would be lost

So, the answer is that hops are, in fact, a preservative.  They are, however, used in "hoppy" beers more for flavor and aroma, which fades over time.  You would be perfectly safe drinking an IPA that has been in your fridge for a few months.  It's just not going to have the clean, bright flavors it would have if drank while fresh.