Dry Hopping to Create Fruity/Tropical Flavors in Beer

by Brad Smith on December 17, 2021 · 1 comment

This week I take a look at some of the recent research into dry hopping during active fermentation to create tropical and fruity flavors in beer.

Fruity IPAs and New England IPAs

There has been an explosion of recent research into hop utilization to maximize fruity and tropical flavors that are characteristic of popular fruity IPAs and New England IPAs.

Some of these IPAs were initially created using very high levels of select varieties of dry hops. However more recent research and techniques have focused instead on adding dry hops towards the tail end of active fermentation.

Biotransformations in Dry Hopping

Brewers and researchers have discovered that certain compounds in select varieties of hops may go through biotransformations in the presence of yeast which creates the desirable fruity flavor compounds. I was fortunate to get summaries of much of this research from Stan Hieronymus.

The key components in this biotransformation appear to be the presence of thiols (3MH/3SH) in the hops along with high levels of geraniol, linalool, and 4MMP/4MMSP, all of which are aromatic oils. Geraniol has a floral, rose or geranium aroma. Linalool has a floral, orange aroma and 4MMP/4MSP has a box tree/current/tropical aroma. Finally thiols, which have been known in wine making for a long time, also have a black currant or muscat aroma.

These various compounds in select hop varieties can be transformed into fruity/tropical aromas and flavor compounds by the yeast near the end of fermentation. For example geraniol is transformed into citronellol, and linalool is transformed into terpineol.

However these biotransformations only occur for hops with thiols present, which generally means they must be American (Pacific Northwest) or Pacific (Australia/New Zealand) hop varieties as most European and English varieties have low levels of the critical oils.

Here are some of the hop varieties that have the highest levels of thiols, geraniol, 4MMP/4MSP:

  • High Levels 4MMP/4MSP (box tree flavors): Citra, Simcoe, Eureka, Summit, Apollo, Topaz, Mosaic, Ekuanot, Galaxy and Nelson Saivin
  • High Thiols/3MH/3SH (grapefruit/passion fruit flavors): Nelson Sauvin, Amarillo, Mandarina Bavaria, Mosaic, Citra, Cascade, Calypso, Tomahawk
  • High Geraniol (fruits/flowery): Bravo, Cascade, Chinook, Citra, Mosaic, Motueka
  • Geraniol Precursor Dominant: Amarillo, Comet, Ekuanot, Hallertau Blanc, Polaris, Summit

To use these hops in a biotransformational way, most brewers are dry hopping near the end of active fermentation or very soon after primary fermentation winds down when there is plenty of yeast available. You don’t want to dry hop too early in the fermentation, however, as the CO2 bubbling up through the beer can strip away some of the aromatics.

I hope you enjoyed today’s article on dry hopping and fruity IPAs. Please subscribe for regular weekly delivery, and don’t hesitate to leave a comment or send this article to a friend.

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{ 1 comment… read it below or add one }

Gabriel Yospin December 19, 2021 at 6:29 pm

Thanks for the awesome summary! Can you provide citations – I’d like to go read these papers for myself… but I don’t want to work too hard to find them 🙂

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