LILLE 2024

Hop aroma in beer is playing an increasingly role in the modern beer world. The craft brewing movement has heralded the renaissance of hop aromas. As a result, brewers worldwide are trying to find their own interpretation of “hop aroma”, either derived by a late hop application in the brewhouse or formulated by the so-called dry hopping technology. These solutions sometimes involving large quantities of hops e. g. in the form of hop pellets, followed by heavy wort or beer losses and technological problems. Hence, a hop aroma product in a concentrated- liquid form was developed. Made from CO2-Extract and just solved in H2O, this invention is showing much higher concentrations of total hop oil compared to pellets. Additionally, due to the water-like flowability major hop aroma components find a fast and nearly complete way into the beer matrix. Advantages in terms of lower volume and material input are evident. The complete absence of hop solids simplifies the application. Further advantages in direct comparison with hop pellets regarding flavour stability in beer can be observed. As a result, the described liquid aroma product was born to achieve an even wider significance.

Along with its important contribution to pleasant aromas in hop-forward beers, there is evidence that dry hopping also imparts amylolytic enzymes able to hydrolyse non-fermentable dextrins into fermentable sugars, resulting in an over-attenuation of the beer in the presence of yeast[1]. Recently, it was shown that this phenomenon known as ‘hop creep’ could refer to a wider range of undesirable enzymatic activities, including esterase[2] and lipoxygenase. In order to improve the stability of dry-hopped beers over time, these residual enzymes were here investigated in different hop varieties and conditionings, according to temperature, ethanol content and beer type. Similar analyses were also applied on different spices often used in craft beers. Among other key-results we evidenced for the first time a strong lipoxygenase activity in some hop conditionings, able to potentially increase the stale flavours.

[1] K. R. Kirkpatrick & T. H. Shellhammer, J. Agric. Food Chem., (2018), 66, 34, 9121–9126 [2] C. Silva Ferreira & S. Collin, J. ASBC, 79, (2021), 259-271

The quality of hops begins to decrease immediately after harvesting; therefore, maintaining the highest possible quality is important A good indicator of hop freshness is the hop storage index (HSI).
The impact of aged hops on the quality and intensity of beer aroma and bitterness in kettle hopped and in dry hopped beers was evaluated. Increasing the boiling time can decrease the difference between samples hopped with hops of different HSI values, suggesting that extending the boiling time causes a loss of some desirable compounds while also hiding some irregularities in hoppy beer aroma. If boiling is conducted for a long enough time, then aged hops are not so problematic from the view of bitterness, since the negative aftertaste caused by oxidation products could be masked by iso-alpha-acids.
Beer samples dry hopped with higher-HSI hops have decreased levels of hop oil components; therefore, the intensity of the hop aroma is lower. With the increase in oxidation products, the quality of the aroma also begins to decline. The quality of bitterness was also reduced and high HSI also led to undesirable gushing.

Hop drying is energy and resource intensive and hop growers must balance the demand for high quality hops with the cost and throughput restrictions created by the kilning process. In the U.S., hop growers typically use deep-bed kilns (60 – 80 cm) and a moderately broad range of temperatures (52 – 62°C). This presentation presents the results from a multiyear, commercial scale hop drying study demonstrating that hop chemistry and sensory properties of American hops are not significantly affected by drying temperature provided there is adequate airflow. In contrast, the biochemical properties are significantly affected by temperature. Higher temperatures do not affect hop aromatic quality but result in lower residual enzyme activity in hops while at the same time decreasing the drying time and improving the overall capacity of the farm. For some varieties, a net reduction in energy demand is achieved at higher drying temperatures. However, this is varietal dependent, since the morphology of some varieties makes them more difficult to dry rapidly. The results presented here offer insight into drying conditions optimization that considers hop quality as well as energy use.