Jeg har også tidligere anbefalt boken nevnt over.
Jeg håper jeg har forfatterens velsignelse til å gjengi forordet, da det er en meget god salgstekst fra StanH
The new IPA
A scientific guide to hop aroma and flavor
By Scott Janis
Foreword by Stan Hieronymus
Foreword
In 2010, scientists working for Japanese brewery Sapporo reported on their research into how geraniol metabolism might add to the citrus flavor of beer. They brewed two beers, using Citra hops in one and coriander seeds in the other because both are rich in the compounds geraniol and linalool. The finished Citra beer contained not only linalool and geraniol but also citronellol, which had been converted from geraniol during fermentation.
The same transformation from geraniol into citronellol occurred during fermentation of the beer made with coriander. Taste panels perceived the beers as relatively similar. The concentration of geraniol and citronellol in both increased depending on the initial concentration of geraniol. The results suggested the importance of citronellol and an excess of linalool in the hop-derived citrus flavor of beer, but because there was little citronellol in raw hops the generation of citronellol depended on geraniol metabolism by yeast.
In 2012, these researchers - whose work you'll find documented in this book - followed up that study by comparing the composition of monoterpene alcohols in various hops. They examined the behavior of geraniol and citronellol under different hopping conditions as well as hop blending conditions influencing the citrus flavor of hopped beer. In the process, they found many U.S. varieties contained relatively high amounts of geraniol, but that European hop varieties did not.
They concluded that a blend of geraniol-rich hops could enrich the levels of geraniol and citronellol in finished beer. They also suggested that citrus character in beer could be enhanced by blend-hopping of geraniol-rich hops; and composition of monoterpene alcohols and flavor character in beer could be controlled by blending two hops having different flavor characteristics. They also provided a chart that showed levels of various compounds in several hop varieties.
Adventurous brewers making hop-forward beers used varieties listed on that chart or information from other sources to find hops rich in geraniol and linalool that might be substituted for hard-to-find varieties. They reported brewing beers that had more citrus-like aromas and flavors, sometimes “tropical" if not as “juicy” as beers made with more expensive New World hops.
Those brewers found a method that worked, but it turns out linalool and geraniol were not totally responsible for the results.
The team from Sapporo, headed by Kiyoshi Takoi, continued to follow up, reporting in 2016 on their discoveries in an appropriately named paper titled, “Control of Hop Aroma Impression of Beer with Blend-Hopping using Geraniol-rich Hop and New Hypothesis of Synergy among Hop-derived Flavour Compounds.” The new hypothesis added thiols-sulfur compounds that, like linalool and geraniol, may be contained in the essential oil of hops - to the equation.
They examined the impact of a volatile thiol, in this case one known as 4MSP or 4MMP, in a model solution with a blend of linalool, geraniol and citronellol. The solution with 4MSP was perceived moderately tropical, while the LGC mix was not tropical but more citrus-like and fruitier. A solution containing both the LGC mix and 4MSP had distinctly tropical character.
Brewers who sought out hops with high levels of geraniol and also picked ones, such as Chinook, containing 4SMP are the ones who reported more tropical aroma and flavor. Those who chose hops with high levels of geraniol but a lower level of 4MSP, such as Bravo, did not.
Is this the final piece in the puzzle? Likely not. The ongoing quest to pack more intense, unique aromas and flavors into beer continues. Brewers keep experimenting, discovering new methods to produce bolder flavors. Scientists keep looking for answers to explain why, and in the process illuminate new pathways to innovation. They will be building on the research documented here.
I’ve read hundreds of papers like the ones that Scott Janish has leaned on to write this book. What they often lack is the perspective that only a brewer can provide. As well as digging through thousands of pages to collect the information within, Janish looks at what he has found through the eyes of a brewer, and he provides other brewers an opportunity to do the same.
He has gone down the rabbit hole, and he’s invited readers to follow.
Stan Hieronymus
Author
Brewing Local (2016), For the Love of Hops: The Practical Guide to Aroma, Bitterness and the Culture of Hops (2012), Brewing with Wheat (2010), and Brew like a Monk (2005)