Free Hops Thiols with Fermentis SafAle™ K-97

Well-known for its subtle fermentation character, Fermentis’ SafAle™ K-97 is often used in brewing lighter beers such as Kölsch’s. However, recent research by the global yeast manufacturer has revealed that this strain can also help accentuate hoppy characters in beer, making it a versatile option for brewers looking to bring out the hops characters in their brews.

We caught up with Nguyen Duc Huy, Fermentis’ Sales Manager for India & SE Asia, and asked him a little more about this yeast strain that’s finding a new lease of life in new age hoppy beers.

ABN: Hi Huy, thank you very much for taking the time to talk with us today.

Huy: You’re welcome. I’m very happy to be here to share more information about SafAle™ K-97 and share some tips on how best to use the strain.

ABN: Great, let’s jump straight to it then. Traditionally this particular yeast strain has been used by brewers for lighter charactered beers, but Fermentis’ latest research has found that it also helps accentuate hoppy characters, can you elaborate on this?

Huy: We have found SafAle™ K-97 to be a very versatile yeast – it’s well known for producing subtle, balanced floral and fruity characters in lighter beers such as Kölsch’s . However, our recent research yeast and hop interaction has shown that it can indeed help emphasize hoppy characters in beer.

During fermentation this strain is able to release hop compounds that may have been previously unperceivable, these being thiols and terpenes. Both compounds can have very powerful aromas; terpenes are responsible for floral aromatic notes such as rose and pine, whereas thiols produce more juicy characters such as passionfruit, citrus and peach. We have found it’s one of the best yeast strains for releasing thiols, making it a great option for heavily hopped beers like hazy IPAs and hop-forward session beers.

ABN: Can you explain more on the process that helps release the hop flavours when using SafAle™ K-97?

Huy: As we know, some hop compounds cannot be perceived in beer at their initial state because they are linked to other molecules, hiding their aromatic and flavourful properties. These are referred to as “thiol precursors”. During fermentation, the yeast breaks the molecular bond and releases those compounds into free thiol form, which makes them readily detectable in the beer.

In addition this strain can interact with and change some of these compounds into acetate forms, producing highly flavourful tropical fruit characters, making it ideal for imparting more hoppy and tropical fruit aromas into your brews.

ABN: According to the SafAle™ K-97 flavour profile chart (above), the strain helps to produce more haziness in beers it is used in. Does that mean it would be a good option for more hop-forward hazy beers?

Huy: Yes, being a good option for more hop-forward hazy beers this is one of the strains we recommend for use in New England IPAs (NEIPAs). Its high flocculation and slow sedimentation helps to maintain the hazy character that is characteristic of this style and as we have seen it performs very well in heavily hopped beers giving more overall hop odour intensity, fruity, hop tropical and citrus aromas. It’s a great yeast to use for balanced fruity & floral character.

ABN: What would be the ideal fermentation temperature for SafAle K-97?

Huy: We recommend the optimal fermentation temperature for this yeast to be between 20°C and 24°C, with a pitching rate of about 50/hl – 80g/hl. The ADF (apparent degree of fermentation) will be about 80-84%.

In the context of producing a NEIPA, our Make Your Choice study on this strain has shown that:

  • Lower pitch rate such as 50g/hl will promote fruity volatiles production.
  • Higher original gravity promotes fruity aromas along with floral character body & alcohol perception.
  • Lower range of temperature such as 20°C may increase fruity volatile concentration along with fruity perception.

ABN: How long do you recommend it would it take, on average, to turn around a complete fermentation and dry hopping with SafAle  K-97?

Huy: This would depend on several factors, such as pitching rate, fermentation temperature, and wort density. However, it would typically take about 6 days to complete fermentation. In our recent Fermentis thiol release study we also found that maturation is mandatory to release free thiols into the beer with optimum results obtained after 3 days at 4°C.

ABN: What advice would you give to brewers wanting to produce hop-forward beers with SafAle™ K-97?

Huy: Brewers should consider the style they are wanting to produce, and also those which are popular with their customers. A NEIPA would be a great option for using this yeast, but other hop-forward styles such as American IPA or Double IPA could also benefit from the SafAle™ K-97’s ability to accentuate hoppy characters.

Consider also the role this yeast will play in the body of the beer you are producing as its turbidity or sugar consumption profile can contribute to the mouthfeel of the beer, especially in styles with “juicy” characteristics.

Above all, I would encourage brewers to experiment and have fun! As with any brewing process, experimentation and creativity can lead to great results. Don’t be afraid to try new things and see how this strain can enhance your favourite hop-forward styles.

ABN: Thank you for that quick insight into SafAle™ K-97 Huy.

Huy: Thanks very much, it’s my pleasure to share these findings. If anyone needs more information please feel free to contact me or your local Fermentis distributor.