Thiol Libre - Sources of Thiol Precursors
Where can I find thiol precursors for use with Thiol Libre?
Hops - some hops such as Cascade, Perle, Saaz, and Calypso have high amounts of bound thiols in them which can be released by Thiol Libre.
If you are planning on mash hopping, we suggest starting at 5 g/L and experimenting with dialling it up to 8g/L. Your bitterness utilization will likely be around 30% (Omega Yeast/Scott Janish). Note that this is a fairly high dosing rate and that hops with stable "spicy" characteristics like Saaz will persist through your brew. Hops like Cascade or Calypso may therefore be more suited to mash hopping although you may need to reduce the dosing rate to avoid high IBU/bitterness.
Grapes - grape products such as Phantasm can be added to the wort to supplement high levels of thiol precursors that can be released by Thiol Libre.
Other sources - There are thiol precursors in several different places. In addition to hops and grapes, malt also has thiol precursors (especially cys-3MH) but it varies from malt to malt. We've seen some big differences and are running a trial now to see which malt produces the most thiol aroma (even without hops). So far it's looking like some local floor malts are contenders. In general, we suspect that lower kiln temperatures and lower mashout temperature might help preserve thiol precursors from malt.
Different fruits also have thiol precursors, grapefruit and guava are likely a good place to start. They both have free thiols but also some locked up.
Want to learn more?
Check out our FAQ and our Blog Post as well as the Guide to Yeast Flavour and Biotransformation.