article written in collaboration with Alexandra Berry.
Understanding the transformation of hops during brewing
Certain hop associations and combinations come more readily to mind than others; the Citra, Mosaic and Simcoe blend, for example, is often found on beer cans or bottles. Similarly, the famous "Four Cs" (Cascade, ChinookCentennial and Columbus) are considered good bases for highlighting hops Aromatic. Why is this?
Source : https://beerandbrewing.com/hops-blending-and-pairing/
How do you choose which hops to use in your brews?
Of course, the selection process starts with Bittering , which is added at the beginning of the boil to obtain the beer's bitterness. For this, the Aromatic profile will be less important, since the oils will evaporate during boiling (although we shall see that this does not apply to all varieties).
To choose aromatic hops, it's important to know their composition and isomerization capacity, in order to predict the aromas present in the finished beer. Knowing the main characteristics of the components of different varieties will enable you to better control the Aromatic potential of your brews, and why not test interesting and original pairings to find particular aromatic nuances.
Chemical components of hops
The molecules present in hop oils will react differently during the brewing process - particularly during cooking and fermentation. For some, heat will develop alpha acids and reduce the potential Aromatic, for others, isomerization will release particular nuances or give rise to Organic transformations and synergies with other varieties, enabling them to be exploited in other ways.
We previously wrote an article dedicated to hop oils, which you can find here.
Terpenes and hydrocarbons
Terpenes are hydrocarbons that are transformed during hop boiling. The best known are Myrcene, Farnesene, α-Humulene, β-Pinene and β-Caryophyllene. These are terpenes with woody and herbaceous aromas, most often found in noble varieties. These varieties are subtle, often with a high bitterness potential, which can be set to hot for isomerization and increased IBU, or cold to preserve the terpenes. Myrcene in particular is quite volatile and not very soluble: it reduces by 50% after 10 minutes of boiling and disappears completely after an hour.
As a result, hops with a high hydrocarbon content are preferred for cold hopping, particularly post-fermentation.
"If it ends in "ene", it doesn't make the scene".
Some hops to recommend: TettnangAdmiral, FuggleWillamette, East Kent Golding, Saaz, Perle...
Monoterpene Alcohols
Monoterpene alcohols are oxygenated compounds. For brewers seeking fruity aromas in their beer, monoterpene compounds are vital. Although present in minimal portions, they are highly resistant to brewing processes.
With their high solubility, they contribute greatly to the aromas found in beer. On the other hand, it's important to note that they retain a certain volatility, and are therefore best used in whirlpools or at the end of the boil to recover these aromas.
The best-known are Linalool and Geraniol. Geraniol will produce very floral aromas with hints of citrus. Although Geraniol can survive the entire fermentation process, it has been shown to convert to β-citronellol during fermentation, which accentuates its lime notes.
Linalool is one of the first oils discovered in hops. It brings notes of exotic fruit and pineapple.
Hops with high monoterpene alcohol content: Bravo, HerkulesBrewers Gold, CentennialColumbus, ChinookEkuanot, PerleMosaic & Simcoe.
Source: https://patspints.com/2021/11/09/understanding-wet-hop-ales-part-1-essential-oils/
Esters derived from hops
Hop-derived esters are also good aroma enhancers, surviving the brewing process. Isobutyric esters are the most common and are often found in very hoppy raw beers. These esters contribute to the beer's final taste.
The 3 main esters are Isobutyl Isobutyrate, Isoamyl Isobutyrate, and 2-methylbutyl Isobutyrate (2MIB).
2-methylbutyl Isobutyrate generally survives the brewing process well, offering aromas of yellow fruit, notably apricot. Isoamyl Isobutyrate and IsoButyl Isobutyrate will have notes of tropical fruit and pineapple.
The hops with the highest ester content after raw hopping are Southern Cross, CascadePacific Jade Mandarina BavariaVic Secret, Nelson Sauvin, l'Amarillo,...
Fatty acids
Hop-derived fatty acids are produced during the aging and oxygenation of hops. It has also been pointed out that hops with a high level of Alpha Acid will have more fatty acids. These can be biotransformed into esters (Ethyl Isobutyrate, Ethyl Isovalerate, and Ethyl 2-Methybutyrate) and can be marked in the taste of the finished beer. They also serve to underline the perception and intensity Aromatic of monoterpene alcohols.
Hops that produce more fatty acids: Apollo, Bravo, Hull MelonEkuanot and Polaris.
It would therefore be interesting to combine them with hops containing high levels of monoterpene alcohols, to further express the fruity, tropical notes of a beer. Some even recommend using Apollo or Bravo hops lightly oxidized in the whirlpool to enhance the transformation of these fatty acids.
Polyfunctional Thiols
Polyfunctional Thiols are the sulfuric compounds desired in the brew for their fruity Aromatic potential. The best-known in beer (and wine, for that matter) are 3-mercaptohexanol(3MH) with grapefruit and rhubarb nuances, 4-mercapto-4-methylpentan-2-one(4MMP) with blackcurrant and ammonia notes in high quantities, and 3-mercaptohexyl acetate(3MHA), which converts to 3MH producing passion fruit aromas.
While 4MMP decreases sharply during boiling, 3MH increases during boiling at 100°C, highlighting aromas when used early in the brewing process!
It's also interesting to look at the synergy of thiols with other chemical compounds: 4MMP has an additive impact on monoterpene alcohols, and notably underlines the tropical aromas of Linalool, Geraniol and β-citronellol.
The varieties to choose for a high concentration of thiols are Citra, Centennial, CascadeMosaic, Nelson Sauvin, Motueka and Sorachi Ace.
Source : https://www.californiacraftbeer.com/wp-content/uploads/2019/09/Hop-and-Yeast-Interactions.pdf
A recap of what we've learned...
- Hops with high levels of monoterpene alcohols (Linalool, Geraniol) can enhance aromas when added in whirlpools. They have very fruity, tropical notes.
- Hop-derived esters impact the taste of the finished beer when used hot. Beware: the yeast strains used have a major impact on aroma.
- Hop-derived fatty acids, often found in lightly aged and oxygenated hops, are interesting from a synergistic point of view: they can underline and amplify the aromatic perceptions of monoterpenes.
- Thiols can be used hot or cold, depending on the levels found, and can also increase the Aromatic tropical potential of certain monoterpenes.
You can find details of the chemical composition of the varieties used to predict theAromatic of your beers.
Source : https://tools.yakimachief.com/docs/Survivable-Compounds-Poster.pdf
These tools will also enable you to know when to prioritize the addition of your hops to your brews, depending on the reaction you want to produce.
Processing hops during brewing
Oils that resist boiling are called "survivables". When selecting hops for your brew and configuring your recipe, it's important to look at the "survivables" content of the chosen varieties to determine when to add them to the brew. Hops with a high concentration of "Survivables" can be added hot, as their composition allows them to survive, transform or even be sublimated by the brewing process.
- Centennial is an excellent hop for whirlpool use, as it has higher concentrations of soluble compounds. These can survive heat and fermentation activity.
Conversely, hops with low concentrations of "survivables" are likely to find greater success and a more positive impact in beer when used later in the process, such as post-fermentation raw hopping.
- Amarillo is likely to have a greater impact in the finished beer if used later in the brewing process.
How to combine hops
Concentrate on balancing high concentrations of "survivables" when creating mixes.
For example, since Loral® is rich in Linalool and Talus™ is rich in Geraniol, these two products are likely to create a beautiful harmony. Loral® and Crystal are both rich in linalool and are therefore likely to create a less dynamic, more one-sided blend.
Source:
Try to concentrate the wort with "survivables" early in the brewing process.
Indeed, high concentrations of "survivables" in the whirlpool and raw hopping during active fermentation can create the conditions for beneficial biotransformation. This releases certain thiols and promotes aromatics. For example Saaz, Perle, Motueka or Hallertauer Mittelfrüh contain precursor thiols (otherwise known as "bound" thiols) that are released during enzymatic transformation.
- The addition of Cascade in the mashing followed by raw hopping during active fermentation of Sabro ® and Simcoe ® is likely to have a huge impact on flavor, as it loads the wort with a diverse set of "raw materials" needed to promote biotransformation.
Source : https://www.badweathertour.com/blog-resources/thiolsmashhopping
So don't hesitate to play around with these hops, combining them to highlight the aromas you want to find in your beers. In a second section, we'll be taking a closer look at the hop combinations you should use to bring out specific flavors in your brews.
Sources:
http://scottjanish.com/survivables-unpacking-hot-side-hop-flavor/
https://patspints.com/2022/06/29/hop-combinations-that-emulate-fruit-flavors/
https://brewhq.com.au/blogs/beer-resources/hop-flavour-guide
https://beerandbrewing.com/hops-blending-and-pairing/
https://www.hopculture.com/top-hops-for-thiols/
https://www.badweathertour.com/blog-resources/thiolsmashhopping
https://patspints.com/2021/11/09/understanding-wet-hop-ales-part-1-essential-oils/
https://brauwelt.com/en/topics/raw-materials/628253-on-the-fate-of-hop-derived-branched-chain-esters