Most of the harvested hops is used in brewing. Hop typically contains a lot of bitter substances, resins and essential oils, which also have antioxidant and antimicrobial effects.
In addition to its traditional use in the brewing industry, it has recently become widely used in cooking. Early spring shoots are added to salads. Dried, ripe hop cones have typical therapeutic effects, which can be used in tea preparations or extracts for different purposes. Hop cleans the blood. This means that it accelerates the process of digestion and excretion. It increases the formation of urine and acts as a sedative. It reduces anxiety and tension. It lowers the heart rate and reduces the symptoms of depression. It acts on sex hormones and the menstrual cycle. It is a mild disinfectant. Hops stuffed pillows and baths are in use as sedatives and sleeping aids. There are various pharmaceutical preparations of hops (tablets, tinctures etc.) already available on the market. Its other known effects are relieving cramps and preventing the onset and development of osteoporosis. Data from various surveys also show its potential use for the treatment of cancer.
Because of its potent antimicrobial action, it could potentially be used in animal nutrition, in which its addition to feed could potentially substitute for standardly used antibiotic additives.
Polyphenols in hop plant parts and their antioxidative and antimicrobial properties
Within the Research Programme Biochemical and Biophysical-chemical characterization of natural substances which is led by prof. Nataša Poklar Ulrih, PhD from the Biotechnical Faculty of the Ljubljana University and is financed by The Slovenian Research Agency, one of the research topics is also identification of bioactive components in hop plant. In collaboration with Barbara Čeh, PhD from IHPS, they are working on identification of polyphenols amount and their identification in different hop plant parts, as well as their antioxidative and antimicrobial potential.
With the growing interest in natural alternatives to synthetic antioxidants, over 980 naturally occurring antioxidants have been identified, with phenolic compounds being dominant, namely. Antioxidants containing phenolic groups are also the most widely used ones. They have the potential to counter or slow down oxidative damage caused by free radicals. You can read about what the research group of this programme found out on this topic in hop cones and leaves in the paper: Relationships between Xanthohumol and Polyphenol Content in Hop Leaves and Hop Cones with Regard to Water Supply and Cultivar – PMC (nih.gov) and also in the paper: A comparison of antioxidant and antimicrobial activity between hop leaves and hop cones. The researchers suggest for hop growing practise to take leaves after the hop harvest when they are collected in a pile next to the harvest hall and up to now represent unexploited plant waste.
The work was done also on white hop shoots; the contents are summarized in a paper: White Hop Shoot Production in Slovenia: Total Phenolic, Microelement and Pesticide Residue Content in Five Commercial Cultivars. These sprouts can be manually harvested in early spring and consumed as a delicacy, akin to asparagus. They are considered to be the first hop plant by-product, as they are removed during regular pruning of the top of the hop root system and are considered as waste. This is why their detected value by our research group is of very interesting importance.
Post-harvest hop residues can be processed into biodegradable and compostable products
Beyond its traditional use in brewing, hop production generates a considerable amount of residual biomass. During harvest, almost the entire above-ground part of the hop plant is removed from the field, and after the cones are separated, large quantities of stems and leaves remain. This biomass is rich in organic matter and nutrients and therefore represents a valuable renewable resource. Its utilisation has traditionally been limited by polypropylene (PP) twine, which remains intertwined with the biomass after harvest and does not degrade during composting.
Within the EU-funded Project LIFE BioTHOP, coordinated by the Slovenian Institute of Hop Research and Brewing (IHPS), a circular approach to hop production was developed by replacing conventional PP twine with biodegradable and compostable polylactic acid (PLA) twine. This makes it possible to use the whole post-harvest hop biomass, including the remaining twine, because it is biodegradable and on-site compostable.
One of the main applications investigated by IHPS was on-farm composting of hop biomass. IHPS tested different composting procedures using approximately 100 tonnes of post-harvest biomass to develop technological guidelines for producing high-quality compost suitable for returning organic matter and nutrients to agricultural soils. In this way, nutrients removed from the hop field can be recycled within the farm, contributing to soil fertility and closing nutrient cycles in hop production.
At the same time, LIFE BioTHOP demonstrated that hop stems and leaves can serve as a raw material for new biodegradable products. Hop biomass was processed into fibres and fibre-reinforced biocomposites and subsequently used to develop products such as horticultural planting pots, cosmetic pots and simmilar. IHPS was directly involved in testing the newly developed biodegradable planting pots in hop plant production. The project also demonstrated the use of transformed hop fibres in biodegradable and compostable bottle packaging. For example, biodegradable, recyclable and compostable wine-bottle packaging containing 50% hop fibres was developed and tested. The project further explored transfer of the developed materials to other applications, including bio-films and products for the agricultural and consumer-goods sectors.
Through LIFE BioTHOP, IHPS and its European partners therefore demonstrated that post-harvest hop biomass can be transformed from an agricultural residue into a valuable resource for organic fertilisation, bio-based materials and biodegradable products. This approach supports circular economy principles by reducing agricultural and plastic waste, recycling nutrients and creating opportunities for new value chains based on hop biomass.
More information is available on the LIFE BioTHOP project website.