Searching the world of hops and brewing to bring you the latest news and research ... so you don‘t have to!
Not only do we humans age in a very individual way
There is a method for determining the freshness of hops, namely the determination of the HSI (Hop Storage Index). This method was developed primarily decades ago to better monitor the degradation of bitter acids. Today, many brewers are interested in information about the stability of the hop aroma of a particular variety. However, this method is not suitable for that purpose. This research team conducted storage trials with the hop varieties Citra, Centennial and Cascade and made some interesting discoveries. The changes in the composition of hop aroma compounds over several years are very variety-specific. Citra proved to be surprisingly stable, even regarding the very reactive free thiols. The changes in terpenes and terpenoids, on the other hand, were very dynamic.
Chenot C, Shellhammer TH. Aging of Citra®, Cascade, and Centennial hops under commercial storage and the discrepancies between sensory quality and HSI classification. Food Chem. 2026 Feb 28;503:147870. doi: 10.1016/j.foodchem.2026.147870. Epub 2026 Jan 5. PMID: 41520373. https://doi.org/10.1016/j.foodchem.2026.147870.
It’s all about the mix
Biotransformation and the release of polyfunctional thiols (PFTs), such as 3-sulfanylhexan-1-ol (3SH), 4-methyl-4-sulfanylpentan-2-one (4MSP), and 3-sulfanyl-4-methylpentan-1-ol (3S4MP), contribute to tropical fruit aromas in beer. This study examined the effect of fermentation temperature (15–30 °C) on PFT production across five commercial yeast strains. Pilot beers were brewed with Cascade hops and analyzed for 29 aroma compounds. Results showed a pronounced, temperature-dependent increase in 3SH (33–72%), with lager yeast at the high temperature (30 °C) reaching the highest levels. However, sensory analysis revealed that elevated thiol concentrations alone did not enhance the tropical aroma. Rather, higher levels of β-ionone, β-damascenone, acetate esters, and terpenoids at elevated fermentation temperatures correlated with a more intense tropical character, especially in the ale yeasts. These findings highlight the complex interactions between thiols and other volatile compounds, demonstrating that higher thiol concentrations alone do not directly result in a stronger tropical aroma profile in beer.
Samia, R. S., Chenot, C., Shayevitz, A., Fischborn, T., & Shellhammer, T. H. (2026). Interactions Between Fermentation Temperature and Yeast Strain: Impacts on Polyfunctional Thiol Release and Beer Aroma. Journal of the American Society of Brewing Chemists, 84(1), 65–76. https://doi.org/10.1080/03610470.2025.2593042
When Are You Truly Mature?
Decisions regarding the right harvest time are extremely important for hop growers and brewers, as the degree of maturity significantly influences hop quality. In this study, the quality of Citra® hops was examined by harvesting weekly at seven different time points from three fields in Yakima Valley, Washington, across three consecutive years. Among other factors, total essential oil content, bitter acid concentration, Hop Storage Index (HSI), the profile of volatile aroma compounds, and the enzymatic activity relevant for Hop Creep (the breakdown of dextrins) were measured. Sensory analyses were also performed. The results show that the content of essential oils, alpha acid concentration, and volatile compounds such as myrcene and linalool initially increase and reach their peak or stabilize in the middle of the season, while the HSI remains relatively constant. Enzyme activity decreases as maturity increases. Early-harvested Citra® hops display grassy and green bell pepper aromas, whereas late-harvested hops develop onion and garlic notes. The preferred Citra samples were those picked in the middle of the harvest: they offer balanced citrus and resinous notes and already reduced enzymatic activity, making this the optimal harvest time.
Jobe CA, Rubottom LN, Shellhammer TH. Investigating the impact of on-bine maturity on the chemical, biochemical, and sensorial characteristics of Citra® hops. Food Chem. 2025 Nov 1;491:145213. doi: 10.1016/j.foodchem.2025.145213. Epub 2025 Jun 18. PMID: 40561770. https://www.sciencedirect.com/science/article/abs/pii/S0308814625024641?via%3Dihub
