Searching the world of hops and brewing to bring you the latest news and research ... so you don‘t have to!
The art of aroma release in beer foam
Everybody trained in beer sensory knows that assessing beer aroma or hop aroma in beer is also challenging due to the foam development when pouring beer into a glass. These Japanese Researchers used a headspace-proton-transfer-reaction time-of-flight mass spectrometer (PTR-TOF/MS) system that combines PTR-TOF/MS with a dynamic and reactive flavour-release monitoring system to measure the orthonasal aroma components in beer before and after foaming. They found that the concentration ratio of each aroma component in beer before and after foaming and the partition coefficient showed a significant correlation, indicating that the concentration ratio of aroma components after and before foaming increased with the hydrophobicity of the aroma components. On the basis of these results, it appears that aroma components with high partition coefficients, such as ethyl hexanoate and ethyl octanoate, might be associated with isohumulones and some proteins and may move to the foam during foaming, where they might be more volatilized by bursting bubbles than those with low partition coefficients. So watch the foam while you smell your beer.
Kaneda, H., Aikawa, T., Matsushita, K., Noba, S., & Kobayashi, M. (2024)2. Beer foam is a carrier of aroma. Journal of the American Society of Brewing Chemists, 82(2), 160-169. https://doi.org/10.1080/03610470.2023.2215686
Thiols in malt
Thiols have been investigated heavily the last ten years. A lot of the research has focussed on hops, where Polyfunctional thiols (PFTs) play an important role for tropical flavours in hop forward beers. PFTs are known to be released by specific yeasts, during fermentation, from bound forms originally found in the raw material. Huge amounts of S-conjugates have been evidenced in several hop varieties. These Belgium Researchers now investigated malts more closely, being the major raw material of beer, and found that malt can also be a significant contributor of PFTs to beer. Forty-two barley malts and five other malted cereals were screened to characterize their thiol precursor profile. They were able to confirme that G-3Shol (Glutathion bound 3-sulfanylhexanol/3-mercaptohexanol 3-MH) was ubiquitous reaching up to 320µg/kg in some samples, whereas Cys-3SHol (Cystein bound 3-sulfanylhexanol/3-mercaptohexanol 3-MH) remained at a trace level of up to 13µg/ kg. No precursors were found in roasted malt. So tropical citrus flavours in beer ultimately may also be malt derived.
Chenot, C., Collin, S., Suc, L., & Roland, A. (2024). Unusual Profile of Thiol Precursors in Special Malts: First Evidence of Chemical Glutathione-/γGluCys- and CysGly-/Cys- Conversions1. Journal of the American Society of Brewing Chemists, 82(1), 15-22. https://doi.org/10.1080/03610470.2023.2187990
Is Direct Analysis in Real Time Mass Spectrometry (DART-MS) the tool of the future for hops?
Evaluation of hops is typically performed by sensory evaluation, requiring a trained human panel, and often yielding subjective results with limited throughput. These US researchers present the use of ambient mass spectrometry (AMS) as an alternative approach to enable objective and rapid chemical fingerprinting of hops for quality screening reflective of sensory. Twelve hop samples were sourced from three different suppliers across four different farms located in Washington and Oregon over two growing seasons Taken together, the results demonstrate that data generated by DART-MS can be used to train a predictive model to accurately classify hops samples based on cultivar and that these cultivar differences may be linked to quality (e.g., sensory). The data generated by DART-MS also show strong potential for classification of hops based on growing location, but more research with a larger number of hop samples is necessary to validate this capability. DART-MS instrumentation is relatively low-cost (of course the instrumentation itself is quite expensive) but once running it requires few consumables, is easy to use, requires minimal to no sample preparation, and offers high-throughput with real time data acquisition. This technology could be utilized for future applications as a tool for hop breeders and growers.
Nasiatka, K. J., Bettenhausen, H. M., Chaparro, J. M., Heuberger, A. L., & Prenni, J. E. (2024)1. Rapid Characterization of Hops (Humulus lupulus) Using DART-MS and Chemometrics2. Journal of the American Society of Brewing Chemists, 82(2), 134-140. https://doi.org/10.1080/03610470.2023.2213238
