Hop Science - July 2025

Well, where are they hiding, the polyphenols?

We know hops is a very valuable source for polyphenols but where do we find which polyphenols exactly in the plant? The phenolic compounds (PCs) of hops are of interest for the food and pharmaceutical industries but require qualitative and quantitative analysis. The aim of this study was to investigate the extent to which phenolic compounds profiles depend on cultivar, plant organ, and plant level. The researchers found that it is not only the plant organ that is important for PC content, but also the level from which it is obtained. Metabolites were investigated in cones, leaves, and stalks at three levels of the plant in Polish hop cultivars (Marynka, Lubelski, and Magnum). The PC content showed a differentiation due to the cultivar of hops, their anatomical part, and position in the plant (level), which reflects the degree of organ maturity. The total PC was the highest in leaves (up to 922 mg/100 g), while lower contents were found in cones (up to 421 mg/100 g) and stalks (up to 105 mg/100 g). The main PCs of leaves were kaempferol-3-glucoside (up to 328 mg/100 g) and rutin (up to 293 mg/100 g), while rutin dominated in cones (up to 209 mg/100 g). These results will help to utilize hop by-products (such as leaves and stalks), which constitute a significant biomass (up to 80%) during the production of cones for the brewing industry. Such an approach contributes to aligning production with the zero waste principle and increasing profitability. In this context, a promising source of PCs are middle and upper hops leaves. On the other hand, knowledge of the quantitative and qualitative PC contents is important for composting of hop by-products.  

Piekara J, Piasecka-Kwiatkowska D, Hołaj H, Jędryczka M, Daniel Daramola O, Dwiecki K. Hop (Humulus lupulus L.) Phenolic Compounds Profile Depends on Cultivar and Plant Organ Maturity. Molecules. 2025 May 29;30(11):2365. doi: 10.3390/molecules30112365. PMID: 40509252; PMCID: PMC12155585. 

More insights in hop creep

A US research team looked at enzymes related to hop creep, using a forced-attenuation assay, as well as microbes that may cause hop creep. Testing individual enzymes and different e​nzyme combinations for attenuation comparable to observed dry-hop additions they were able to get some very good insights. Also microbes from hops were grown under anaerobic conditions and tested for diastatic power. Results show and confirmed from other studies that β​-amylase alone most closely resembled dry-hop additions in the amount of attenuation and that a combination of limit dextrinase and β-amylase over attenuated the beer. Of the grown microbes, none were able to attenuate beer to the same degree as β-amylase or hops. Finally, a dilution series of dry-hopped beer of up to 1:10,000-fold dilutions showed that attenuation decreased with increasing dilution, but some samples retained high attenuation despite a high degree of dilution.  

Connor T. Murphy, Jaelyn Nye, and Gregg Johnson. An Investigation of Enzymes and Microbes in Hop Creep, MBAA TQ Vol 62 2025, pp6-10, TQ https://doi.org/10.1094/TQ-62-0115-01​ 

Nonthermal preservation of beer – the future?

Nonthermal preservation methods have gained traction in the brewing industry as sustainable alternatives to traditional thermal pasteurization techniques due to their ability to inactivate spoilage organisms and improve microbial safety while preserving the sensory qualities of beer. High-Pressure Processing (HPP) is a groundbreaking food-processing innovation using pressures of 200 to 600 MPA to inactivate microorganisms while preserving the natural characteristics of the relevant food/beverage. HHP pasteurization using up to 600 MPA effectively inactivates spoilage yeasts and bacteria in beer. Pulsed Electric Fields (PEF) inactivates microorganisms quickly and at low temperatures also preserving the product quality. It is able to permeabilizes cellular tissue in microseconds and effectively inactivates microorganisms by increasing the transmembrane potential in cell membranes leading to electroporation and cell death.  The method effectively inactivates and log reduces dormant yeasts, lacto bacteria and others. Another method, high-pressure CO2 treatment (DPCD) is known to effectively inactivate spoilage microorganisms and enzymes in food below 50 MPA while also preserving all quality parameters. It is used to pasteurize fruit juices and also beer. Understanding the strengths and weaknesses of these methods is crucial for determining their feasibility in large-scale brewing operations. And of course the hops help! 

Milani, E., et al: Nonthermal Preservatin of beer: sustainable alternative for thermal pasteurization, MBAA TQ, Vol 62, 2025, pp 11-15 ;