Bulk properties of densified hop cones related to storage and throughput measurements

•Densification experiments with wet and dry hop cones of different varieties.•Differences in densification parameters among the tested varieties were observed.•Densification process of wet hops increased pressure-density slope about 3.5×.•Pressures for double value of the initial density were different for most of tested varieties.•Found differences could influence hop harvesting and post-harvesting technologies.

Hop is one of the most important materials for beer production. Nevertheless the material density of hop is little known even though this information is needed for the harvesting, processing and storage of the hop cones. To fill this gap in knowledge, densification experiments were carried out during 2013 harvesting season with wet and dry hop cones of different varieties. It was shown that for hop cones of all varieties in dry state that pressure increased with increasing material density. In a wet state, Sladek and Vital varieties showed different behaviour. Higher initial densities meant greater hardness of those two varieties. The densification process caused significant increase in the densification curve slope at the initial and final points. The initial slope was very high for the Sladek and Vital varieties in a wet state. Resulting pressure values were statistically different for most of the tested varieties. The differences in densification parameters were in all cases transferred from the wet to dry states. Differences found between varieties can significantly influence hop material throughput during harvesting as well as the behaviour of hop cones during post-harvest processing and storage.