I found the answers - and much more - in: "IPA Evolution" by Amelia Khatri, which is a very good introduction into this subject. According to the publisher the book was written with the assistance of AI.
Here is what I learned: In the past water was often unsafe to drink, making beer, with its boiled and fermented nature, a much safer alternative. Before the 18th century people distinguished Ale from Beer. While Ale was typically unhopped or very lightly hopped, Beer included hops as bittering and a preserving agent.
IPAs are based on the traditional "Pale Ale", that is -beginning in the 18th century in England - barley malt fermented with the help of yeast. Ale is different from Lager: Ale ferments at warmer temperatures, which results in a faster fermentation and yield fruitier, more complex flavors, Lagers are brewed at colder temperatures, resulting in a cleaner, crisper, and often lighter-bodied beer.
In the 19th century English brewers started to produce a new version, called "India Pale Ale", specially for the market in India. Before the Suez Canal was opened, the beer had to travel more than 3 months in challenging conditions, especially high heat. Unfortunately beer doesn`t age well. In order to make the beer more resistant the brewers chose a higher alcohol content and added more hops, to preserve it better for bacteria. "The higher alcohol content inhibited the growth of spoilage bacteria, while the hops provided antimicrobial properties and contributed to the beer´s characteristic bitterness." The aging process during the long ship traffic to India "essentially transformed the beer into a distinctly different product than what was originally brewed in England".
Scent Of A Forest
The addition of hops did not just to make the Ale more resistant against heat & unfriendly bacteria, it also made it more bitter and spicy. Today hops are also chosen for their contributions to flavor, aroma and bitterness. These contributions stem from from two main categories of compounds: essential oils, responsible for aroma, and alpha acids, precursors to bitterness.
Hundreds of different compounds can be found in hop essential oils, but a select few play a dominant role in shaping the aroma profile. Terpenes are the most abundant class of aroma compounds in hops. Some of the most important terpenes in hops include: Myrcene, which contribute earthly, herbal and slightly resinious aromas. High levels of myrcene can lend a "dank" or "cannabis-like" character in beers. Humulene, which is responsible for woody, spicy, and earthy notes. It is also believed to contribute to hop`s anti-inflammatory properties. Caryophyllene, which boasts a spicy, peppery, and woody aroma. Limonene, which provides bright citrusy aromas. Pinene, which deliver piney and resinous aromas, evoking the scent of a forest.
Besides the terpenes there are other oil components that contribute to the overall sensory experience: Esters, that are often formed during fermentation, create fruity and floral notes. And Thiols contribute surprisingly potent aromas, ranging from tropical fruit (passionfruit, guava) to savory (garlic, onion).
There is a chapter describing different varieties of hops and their tastes. Often the hops are named on beer cans, and many pubs also name the hops in the beers they have on tap. Cascade hops is considered the grandfather of American aroma hops. This variety offers distinct grapefruit and floral notes, especially popular in West Coast IPAs. The taste is caused by a combination of limone, myrcene and other terpenes.
Centennial is known for its pronounced citrus character, particular lemons. Citra delivers intense grapefruit, lime and passionfruit aromas. Simcoe offers a more complex aroma profil, with a note of pine, grapefruit, and passionfruit. Amarillo contributes orange and grapefruit notes, along with a touch of floral aroma.
Another chapter focuses on New England IPAs (NEIPAs) which own a hazy appearance and juice flavor profile. One of the most crucial elements of this kind is the selection of yeast. Unlike traditional yeasts Ale yeasts that ferment cleanly and produce little in the way of flavor compounds, NEIPA brewers favor strains renowned for their ability to produce fruity esters (a chemical compound formed when an alcohol reacts with an acid) - the aromatic compounds responsible for notes of peach, mango, and pineapple. Yeast strains like Conan, London Ale III, and Verdant IPA are popular choices.
NEIPAs rely on heavily and late-addition hopping, meaning that the majority of hops are added towards the end of the boil or even after fermentation has begun (known as dry hopping). This minimizes the extraction of bitter alpha acids, allowing the more delicate aroma compounds to shine through.
Science & Art
Today IPAs are the product of science & art, especially American IPAs. The scientist in the brewer tries to understand the different varieties of hops that come with different oils that are extracted through the brewing process.
The beer scientists also varie different kind of yeast, which not only supports the fermentation process, it also added flavors. Last but not least the brewers perform water chemistry. They often adjust the mineral content of their water to enhance the hop aroma and soften the beer`s overall profile. Higher chloride levels, for example, can accentuate the perceived sweetness and juiciness of the hops.
For the production of Hazy IPAs the brewers use protein-rich grains like oats and wheat, specific yeast strains that remain suspended in the beer, and the interaction of hop oils and proteins.
Modern craft brewers are also artists who combine the ingredients to find a balance between the sweetness of the malt and the spiciness and other flavors of hops & yeasts. Today they use technologies like senors & software to measure and fine-tune temperature and status of fermentation process.
Brewers often use a technique called "hop bursting", adding massive quantities of these hops in the final minutes of the boil or during the whirlpool (a process that separates the worst from the spent grain) to maximize aroma intensity.
Agent Of Transformation
I found much more information, for instance:
Mashing is the crucial process that transforms malted grains into a sugary liquid called wort. It involves mixing crushed malt with hot water and holding it at specific temperature to activate enzymes that convert starches into fermentable sugars. Different enzymes are active at different temperatures. Mashing at lower temperature (around 148-156 F or 64-69 C) favors the production of fermentable sugars, resulting in a drier, lighter-bodier beer. Mashing at higher temperature (around 158-168 F or 70-76 C) favors the production of less fermentable sugars (dextrins), resulting in a sweeter, fuller bodied beer.
There are two primary mashing techniques: infusion mashing and decoction mashing. Infusion mashing involves adding hot water to the malt to reach the desired temperature. Decoction mashing involves removing a portion of the mash, boiling it, and then returning it to the main mash to raise the temperature. Decoction mashing can contribute a richer, more complex flavor to the beer.
Yeast is a powerful agent of transformation, shaping the beer´s flavor, aroma, and overall character. During fermentation yeasts produce specific flavor compounds, like esters and phenols. They also produce alcohols, aldehydes and diecetyl. Diacetyl, a dioketone, can impart a buttery or butterscotch-like flavor.
Prohibition in the US (1920-1933) decimated the brewing industry. When brewing resumed, only the largest and most financially stable breweries could afford to re-establish themselves, further accelerating the consolidation trend. As larger breweries prioritized Lagers, Ales like IPA were often seen as too niche, too expensive to produce, or too difficult to market. The beer landscape became increasingly dominated by bland, mass-produced Lagers.
The bitterness of beer is measure in International Bitterness Units (IBUs).
The term "session beer" originated in Britain, referring to beers that could be consumed of an extended drinking session without causing undue intoxication
The popular image of a witch stirring a cauldron is thought by some to be misrepresentation of alewives brewing beer! Their pointed hats may have been worn to stand out in the marketplace, and the "cauldron" was simply the brewing kettle".
The book has much more information about beers and the complexities of the different brewing processes. There are some repetitions, but the book is elegantly written and partly humorous; it seems that there were human contributions. Unfortunately the publication disappeared from Amazon`s website, but I still could find it on Google. Maybe some AI hating luddites are suing against the publication.
A cheers on AI!
