Why Are IPAs So Bitter?

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The average human has 10,000 taste buds, each packed with 150 receptors to process flavors from food, drink, and other things we put in our mouths. Of the five broad sensations we can detect — salty, sour, sweet, bitter, and umami — bitterness is the flavor we’re not born to love.

Many naturally occurring toxins taste bitter to us, so our instinctive aversion to the flavor may have saved the lives of our foraging ancestors. Which, given the state of craft beer world, might cause you to question the sanity of the average palate. While plenty of drinks have natural bitterness, even the earthiest Bordeaux or bitters-heavy Manhattan don’t compare to today’s average Imperial IPA. But why?

The origins of bitterness in beer started in 822, A.D., with the first recorded use of hops. But it wasn’t until a full millennium later — 1822 — when today’s infatuation with alpha acids from the Lupulin gland of the hop got its biggest boost. The East India Company, tasked with supplying British troops and colonists in the Indian subcontinent with the comforts of home, was getting complaints that porters arriving in Calcutta were not drinkable. The company decided to ship Bow Brewery’s October Stock Ale to India. This higher gravity, generously hopped pale ale normally took two years to mature. But thanks to six months in the steamy hold of a ship on the high seas — the very conditions that had destroyed porters — the beer was ready for drinking when it arrived in India. It did not hurt that hops have anti-bacteria properties and act as a natural preservative. Even with the extra level of bitterness, IPA became a hit because it was a much needed thirst quencher for Englishmen not accustomed to triple digit temperatures. Troops returning to the British Isles after their tours of duty started demanding IPA.

The American craft beer revolution that started in the 1980s then cranked up the International Bittering Units (IBUs) that brewers use to measure bitterness. “The ratio between original gravity and IBUs has gotten a lot higher in the last 20 years with American IPAs,” says Ray Daniels, founder of the Cicerone Certification Program (think beer sommelier). Not long ago a big IPA was 40–50 IBU, and now beer fans long for 70 IBU IPAs. 

It’s a rare brewpub that doesn’t have at least one IPA on draft, and many have several. IPA is the most popular category for brewers to enter at the Great American Beer Festival and World Beer Cup. Winning a medal in the IPA category is a marketing coup that puts a brewery on the map. There’s even an annual competition — the Alpha King Challenge — celebrating IPA bitterness. Last year’s winner, Uberbrew Double Tap Tactical IPA from Billings, Montana, has hops added no less than seven times during the brewing process.

“American-style IPA is way more hop-forward than British IPA. It’s not just bitterness, it’s about hop flavors and aroma,” says Blaze Ruud, with Yakima Chief-Hopunion, a global supplier of hops. There are around 100 hop varieties actively being used by commercial brewers today. And just like different grape varietals impact wine characteristics, each hop style imparts different floral, citrus, spice, and earthy notes as part of its bitterness profile.

Ruud, who was an award-winning brewer at Old Schoolhouse Brewery in Winthrop, Washington, before joining Yakima Chief-Hopunion, says even now our appreciation of bitterness is evolving and brewers are adjusting techniques. Instead of adding the bulk of hops in the initial boil, brewers are “hop-bursting” ales by adding hops after the wort has cooled and placed in the fermenter. The result is more concentrated aromas and flavors, with a lower total IBU. In other words, brewers are continuing to push the limits of our taste for bitterness. 

Getting to Know Bitter: A Home IPA Experiment

If you're new to IPAs, pick up these American classics, each with plenty of IBUs but different flavor profiles, and sample them side-by-side.

Bell’s Two Hearted Ale (Michigan): Brewed exclusively with Centennial hops, this 7.0% abv beer has pine and grapefruit flavor notes. Dry hopping adds complexity to this 55 IBU ale.

Dogfish Head 60 Minute IPA (Delaware): Continuously hopped for 60 minutes using a blend of Northwest hops, this is a 60 IBU, 6.0% abv IPA displays citrus and grassy flavors.

Stone Ruination Double IPA 2.0 (California): This double IPA packs a 8.5% abv punch and weighs in at more than 100 IBU, thanks to huge amounts of Magnum, Nugget, Centennial, Simcoe, Citra, and Azacca hops. Expect intense citrus aroma and a palate-blasting piney flavor.