Disintegration of Hop Pellets during Dry Hopping

Abstract

Dry hopped (craft-)beers with pronounced hop aroma profiles reported increasing sales figures. For dry hopping, hops are commonly added during fermentation or maturation as whole hops or powder, but mostly as pellets. Since dry hopping is a mass transfer of aroma compounds, the process of pellet disintegration is of significant importance. Fast swelling hop pellets that show a small particle size distribution and therefore a large surface area are regarded as ideal for dry hopping. This work presents data regarding the disintegration process of hop pellets including swelling velocity, swelling volume, surface roughness during swelling, sedimentation velocity, and particle size distribution. Swelling velocities are found to be highly temperature dependent whereas swelling volumes are depending on alpha acid level of the hop variety. Particle size distributions show no significance regarding hop variety but mean particle sizes are considerable smaller for pellets in comparison to hop powder. Obtained results enable the suggestion of dry hopping strategies that can lead to a higher yield and therefore beer with lower solids concentration at a more distinct hoppy aroma.