Un­der­stand­ing Bit­ter­ness

Sev­eral years ago, brew­ers at The Bos­ton Beer Com­pany ran tri­als to de­ter­mine how com­mon spices changed per­ceived bit­ter­ness in var­i­ous Sa­muel Adams beers. What they found serves as a re­minder that there’s more to bit­ter­ness in beer than iso­mer­ized al­pha

Craft Beer & Brewing Magazine - - Contents - By Stan Hierony­mus

Sev­eral years ago, brew­ers at The Bos­ton Beer Com­pany ran tri­als to de­ter­mine how com­mon spices changed per­ceived bit­ter­ness in var­i­ous Sa­muel Adams beers. What they found serves as a re­minder that there’s more to bit­ter­ness in beer than iso­mer­ized al­pha acids and that there’s more to mea­sur­ing in­ter­na­tional bit­ter­ness units than those iso­mer­ized com­pounds.

FRUS­TRAT­ING AS BREW­ERS FIND it, any ef­fort to mea­sure bit­ter­ness an­a­lyt­i­cally com­pli­cates it. Per­ceived bit­ter­ness? Qual­ity of bit­ter­ness? Th­ese are the do­main of sen­sory pan­els. With the cur­rent tech­nol­ogy, says hops sci­en­tist Val Peacock, ma­chines are not ready to re­place tast­ing pan­els. “I hope to be proven wrong in the next ten years,” he says. “My goal in life is to prove my­self wrong.”

Brew­ers who are adding in­creas­ingly large quan­ti­ties of hops late in the brew­ing process, par­tic­u­larly post boil, have made the math more com­pli­cated. In­tent on max­i­miz­ing the im­pact of aroma, they are chang­ing the ma­trix of bit­ter­ing com­pounds in ways sci­en­tists had lit­tle rea­son to in­ves­ti­gate un­til now.

IBU, Hops, and Bit­ter­ness Aren’t Syn­onyms

The ele­phant in the bit­ter­ness room is the IBU, orig­i­nally an acro­nym for in­ter­na­tional bit­ter­ness unit, but now often a syn­onym for “brewer used a lot of hops.” It is de­ter­mined by acid­i­fy­ing and ex­tract­ing a sam­ple of beer, then tak­ing an ab­sorbance read­ing at a spe­cific wave­length with ul­tra­vi­o­let light.

The pro­ce­dure must be per­formed in a lab, and the re­sult is an ab­so­lute, a sin­gle num­ber that is gen­er­ally mis­un­der­stood.

To es­ti­mate IBUS, a for­mula emerged more than fifty years ago as a com­pro­mise among brew­ing sci­en­tists on both sides of the At­lantic. (Many small brew­eries, as well as home­brew­ers, use for­mu­lae or soft­ware to cal­cu­late IBUS. The great­est weak­ness of such tools is that uti­liza­tion is a key com­po­nent, is often brew­ing-sys­tem spe­cific, and is sel­dom well cal­i­brated.)

When the for­mula was de­vel­oped, most brew­eries used baled hops, and the hops were not nearly as fresh as pel­lets—the form most brew­eries use—are to­day. Al­though most of the hops bit­ter­ness came from al­pha acids iso­mer­ized by boil­ing, a cer­tain per­cent­age re­sulted from ox­i­da­tion prod­ucts. The method ad­justs the sum of iso-al­pha acids and non-iso hops ma­te­rial by a fac­tor of five-sev­enths, based on the as­sump­tion that five-sev­enths of the bit­ter­ness of an av­er­age beer in the 1960s re­sulted from iso-al­pha acids and the rest from non-iso hops ma­te­rial.

“IBU will mea­sure what­ever is ab­sorbed at that [spec­i­fied] length,” says Peacock, formerly of An­heuser-busch and now an in­de­pen­dent con­sul­tant. “The more com­pli­cated the hopping method, the more de­vi­a­tion from mea­sur­ing pure [iso-al­pha acids].”

Bos­ton Beer’s tri­als il­lus­trate how even non-hops mat­ter can al­ter the re­sults. Brew­ers made a base beer with hops cal­cu­lated to con­trib­ute 20 IBUS be­fore it was dry spiced for seven days with one pound per bar­rel (3.8 grams per liter) of co­rian­der, co­coa nibs, dried le­mon peel, cof­fee beans, or cin­na­mon. The IBUS in the con­trol sam­ple then mea­sured 26, the one spiced with co­rian­der 27, the one with co­coa nibs 24, and the one with cin­na­mon 80 (yes, eighty).

Nine of the twelve trained pan­elists rated the cin­na­mon beer as more bit­ter than the con­trol, and none found it less bit­ter. Seven called the co­rian­der beer more bit­ter, com­pared to three who called it less; and seven rated the cof­fee beer (29 IBUS)

The ele­phant in the bit­ter­ness room is the IBU, orig­i­nally an acro­nym for in­ter­na­tional bit­ter­ness unit, but now often a syn­onym for “brewer used a lot of hops.”

more bit­ter, four less. The one with co­coa nibs was the most po­lar­iz­ing. Six found it more bit­ter, six less.

Those are just a few of the many non­hops in­gre­di­ents that may change beer bit­ter­ness or the per­cep­tion of bit­ter­ness. In ad­di­tion, ge­net­ics play a ma­jor role in de­ter­min­ing why one beer drinker may per­ceive bit­ter­ness dif­fer­ently than the next. “Just like some peo­ple are color blind, some peo­ple are taste blind and sim­ply can’t taste bit­ter things that oth­ers can,” says John Hayes from Penn State’s Col­lege of Agri­cul­tural Sciences. “It turns out that dif­fer­ent bit­ter foods act through dif­fer­ent re­cep­tors, and peo­ple can be high or low re­spon­ders for one but not an­other.” A per­son highly sen­si­tive to one bit­ter com­pound may be in­sen­si­tive to an­other.

The “Other” Al­pha Acid

Many brew­ers are just learn­ing about hu­muli­nones, a mi­nor hops acid that can have a ma­jor im­pact on bit­ter­ness in heav­ily dry-hopped beers. Hu­muli­nones are formed by the ox­i­da­tion of al­pha acids. Pel­lets con­tain a higher con­cen­tra­tion of hu­muli­nones than baled hops. Dried hops with a higher Hop Stor­age In­dex (HSI) have a higher con­cen­tra­tion of hu­muli­nones. This is va­ri­ety de­pen­dent.

Hu­muli­nones are about two-thirds as bit­ter as iso­mer­ized al­pha acids, but they are more sol­u­ble and will dis­solve into beer dur­ing dry hopping to in­crease bit­ter­ness. How­ever, that doesn’t nec­es­sar­ily mean heav­ily dry-hopped beers will taste more bit­ter or even that they will con­tain more IBUS. Re­searchers at Hop­steiner have found that dry hopping re­duces the amount of isoal­pha acids that end up in fin­ished beer.

Com­par­ing a low-ibu beer to a high-ibu beer in or­der to un­der­stand the sol­u­bil­ity char­ac­ter­is­tics of hu­muli­nones pro­duced this sur­pris­ing re­sult. In­creas­ing the dry hopping dose from 0 to 0.5, 1.0, and 2.0 pounds per bar­rel re­sulted in pro­gres­sively lower iso-al­pha acid con­cen­tra­tions, from 48 to 39, 35, and 30 parts per mil­lion, re­spec­tively. “This sig­nif­i­cant loss in bit­ter­ness was off­set, how­ever, by the large in­crease in hu­muli­nones that dis­solved in the beer,”

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