Science is once again enhancing the complex flavor in brewing. Thiols have been the talk of the brewing world for some time, and these compounds can be found naturally in various agricultural products and foods. This family of sulfur-containing aroma compounds are also naturally found in hops, and there are two types — free aroma-active volatiles (free thiols) and non-aroma-active precursors (bound thiols). These thiols are so small they represent only 1% of the total hop oil composition, but they can give big results. Free thiols specifically can be responsible for contributing big tropical aromas that are popular in today’s juicy or hazy IPAs, while bound thiols are (sad trombone) odorless.
BUT, what if those bound thiols could be unbound? From White Labs website (experts in yeast and fermentation for food and beverage):
Free thiols, which are often responsible for contributing tropical aromas, are present in some of the most popular hops. However, many other hop varietals can contain higher amounts of odorless bound thiols. Yeast interactions from high B-lyase [enzyme] strains with these varieties of hops have been found to release these bound thiol compounds to free thiols resulting in new tropical aroma.
This process is called biotransformation: It’s where a specific type of yeast is used during fermentation — one that produces specific enzyme activity (like B-lyase) — to transform compounds in hops and perhaps other products like malt to create more desirable flavors and aromas. These yeast strains are being identified and genetically modified to activate those bound/precursor aroma-enhancing thiols during beer production, and they are being matched with hops that have high amounts of bound thiols (Cascade, Saaz, Calypso and Perle for instance) and techniques like mash hopping to get the best results.
An example of such a yeast from White Labs would be WLP077 Tropicale, which is a blend of non-GMO yeast strains that have been carefully selected to aid in the release of bound thiol compounds by targeting high enzymatic B-lyase activity.
White Labs is noting this yeast helps bring out those tropical flavors and aromas such as passionfruit, grapefruit and mango — perfect for a juicy or hazy IPA. To create these types of interactions, White Labs has created a yeast blend that not only causes high activity for biotransformation but also provides an all-natural blend that contributes to the balance of aroma and flavors. Go out and experiment with this new blend and see what new flavors and aromas can be unlocked in hops via yeast. There’s more info in the video above or surf right over here.
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