Effect of Densification Conditions on Specific Energy Requirements and Physical Properties of Compacts Made from Hop Cone

Niccolò Pampuro,Patrizia Busato,Eugenio Cavallo

doi:10.3390/en11092389

Abstract

Hop cones, due to their essential flavor, are one of the four main ingredients for beer production. The paper reports the results on an investigation of the densification process of hop cones. This experiment investigated (i) the effects of compression pressure in the range of 40 to 80 MPa and pressure application time in the range of 10 to 40 s on the final density and durability of the compacts made from hop cones and ii) the specific compression energy required for the process. The specific compression energy requirements to compact hop cones ranged from 14.20 to 24.48 kJ kg−1. The final compact density values ranged from 515.2 to 876.6 kg m−3, while the durability percentage calculated ranged from 71% to 91%. The obtained results highlighted that compression pressure—in the range of 40–80 MPa—significantly affects the specific compression energy requirements, the final density and the durability of the produced compacts. In this experiment, pressure application time plays a key role in determining compacts density, while did not affect durability and compression energy requirements. Considering the specific compression energy values calculated in this experiment, it can be stated that the pressure agglomeration method described to compact hop cones is more efficient than pelletizing process which is typically characterized by specific energy values ranging from 19 to 90 kJ kg−1.

Highlights

Hop (Humulus lupulus L.) is a spontaneous plant in central Europe, nowadays, widely cultivated in all temperate areas [1]
Considering the high energetic input to form hop cones pellet, this paper reports studies aimed at investigate alternative densification process of dry hop cones
The results obtained highlighted that compression pressure—in the range of

Summary

Introduction

Hop (Humulus lupulus L.) is a spontaneous plant in central Europe, nowadays, widely cultivated in all temperate areas [1]. The bitter hop-compounds (approximately 17–55 ppm of iso-a-acids), being toxic especially for Gram-positive bacteria, contribute with the ethanol to build an unfavourable medium for many microorganisms [4]. These properties have been used for many centuries but nowadays hops are included into to brewing recipe to give the beer its specific hallmarks with the flavours of the selected hops: traditional aroma varieties are responsible for spicy or herbal ‘noble hop aroma’ while flavour hops give tropical fruit, citrus, pine, or flowers aromas in beer [5].

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