Pale Ale & IPA
From Burton Bitter to West Coast IPA to Hazy NEIPA — the complete family of pale, hop-forward ales and their chemistry.
Pale Ale is a category of ale brewed primarily with pale malts and characterised by noticeable hop bitterness, flavour, and/or aroma. The term encompasses a broad range from low-to-moderate bitterness English Bitter (also called Ordinary Bitter or Best Bitter) and English Pale Ale, through to American Pale Ale (moderate hop character, clean malt base) and India Pale Ale (IPA) — a subcategory defined by elevated hop bitterness and/or aroma, historically developed for export from Britain to India (the higher hopping provided antimicrobial stabilisation during long sea voyages). Modern IPA has evolved into numerous substyles: English IPA, American IPA, Double/Imperial IPA (DIPA), West Coast IPA (dry, resinous, high bitterness), New England/Hazy IPA (NEIPA — low bitterness, very high late hop aroma, hazy/turbid appearance). All are ales (top-fermenting Saccharomyces cerevisiae). Primary source classification: BJCP 2021 Styles 12A (British Golden Ale), 11B (Best Bitter), 12C (English IPA), 21A (American IPA), 22A (Double IPA), 21C (Hazy IPA).
Why pale ale exists — the malting revolution
Before the 18th century, almost all beer was made from malt dried over wood or straw fires — which produced brown, heavily roasted malt with flavours of smoke, chocolate, and coffee. In the early 1700s, coke-fired (coal-derived fuel) kilning was developed in England, producing the first pale malt — lightly kilned, very light in colour, with more fermentable sugar than dark malts (as roasting destroys fermentable sugars). Pale malt produced beer that was simultaneously clearer, lighter, more carbonated (due to corks becoming common in glass bottles), and more hop-forward — because with pale malt, hops could contribute bitterness and aroma without competing with roasted flavours.
Pale ale became fashionable by the mid-1700s, particularly from Burton upon Trent — where the sulfate-rich local water chemistry (high calcium sulfate, gypsum) enhanced hop bitterness perception and produced a drier, more angular Pale Ale character than could be achieved with London's softer water. This "Burtonisation" (the deliberate addition of gypsum to brewing water) remains a practice today.
What IPA actually is — the history documented
IPA (India Pale Ale) is documented as having been developed in Britain in the late 18th–early 19th century for export to India and other British territories. Pale ales brewed with higher hop rates and higher alcohol (hops and alcohol are both preservatives) survived the 4–6 month sea voyage to India better than less-hopped ales. The Hodgson brewery (Bow, East London) is historically associated with the early export trade to India, and Allsopp (Burton) became the dominant supplier from the 1820s onwards after receiving information about Hodgson's recipes through the East India Company.
The IPA category declined in the late 19th century as refrigeration and lager brewing spread globally. It was revived and radically transformed by American craft brewers from the 1980s onwards — particularly West Coast brewers (Sierra Nevada, Anchor, Stone) who used American hop varieties (Cascade, Centennial, Chinook) producing very different aromatic compounds (citrus, pine, resin) from English hops (earthy, floral, herbal). The New England IPA (NEIPA) revolution of the 2010s further transformed the style — using massive quantities of late/dry hops at below-bittering-threshold temperatures, producing low-IBU, hazy, extremely aromatic beers dominated by thiol and ester compounds.
BJCP pale ale and IPA styles — documented specifications
| Style | IBU | SRM | ABV | Character |
|---|---|---|---|---|
| Ordinary Bitter (11A) | 25–35 | 8–14 | 3.2–3.8% | Low strength, high drinkability. Earthy English hops. Caramel malt. Cask/real ale tradition. |
| Best/Premium Bitter (11B) | 25–40 | 8–16 | 3.8–4.6% | The classic English pub ale. More hop flavour than Ordinary, still caramel malt base. |
| English IPA (12C) | 40–60 | 6–14 | 5.0–7.5% | More bitter than Bitter, but with English hop character. Lower ABV than American IPA. |
| American Pale Ale (18B) | 30–50 | 5–10 | 4.5–6.2% | American hops (citrus, pine). Clean malt base. The gateway Pale Ale of the US craft movement. |
| American IPA (21A) | 40–70 | 6–14 | 5.5–7.5% | High bitterness, hop-forward. Citrus, pine, resin from American varieties (Cascade, Centennial, Simcoe, Citra). Dry finish. |
| Double IPA (22A) | 60–120 | 6–14 | 7.5–10% | Very high ABV and bitterness. Large malt body to balance. Extended hop additions. |
| Hazy/NEIPA (21C) | 25–60 | 3–7 | 6.0–9.0% | Low-bitterness, very high late-hop aroma. Thiol and ester compounds dominate. Hazy appearance from dry-hopping proteins. Tropical, juicy, soft mouthfeel. |
Hop chemistry — why American hops smell different from English hops
Hop aroma in beer comes from a complex mixture of terpene hydrocarbons, terpene alcohols, esters, and thiols present in hop lupulin glands. English hop varieties (Fuggles, East Kent Goldings) are characterised by high myrcene, linalool, and geraniol concentrations — producing earthy, floral, herbal aroma. American varieties (Cascade, Centennial, Citra, Mosaic, Simcoe) have distinctly different aromatic profiles: Cascade is characterised by high geraniol and linalool but with a distinctive citrus/grapefruit note from specific ester compounds; Citra contains high concentrations of 4-mercapto-4-methylpentan-2-one (4MMP) — the same blackcurrant/tropical thiol compound documented in Sauvignon Blanc. Hazy NEIPA's extreme tropical aroma is partially attributed to these polyfunctional thiols released from hop precursors during dry-hopping, particularly when free thiols in the hop interact with yeast biotransformation during active fermentation. Source: Praet et al. (2016), MBAA Technical Quarterly; Lafontaine and Shellhammer (2018), JAFC.