Tag Archives: hop

723-727 P. Heřmánek, A. Rybka and I. Honzík
Determination of moisture ratio in parts of the hop cone during the drying process in belt dryer
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Determination of moisture ratio in parts of the hop cone during the drying process in belt dryer

P. Heřmánek*, A. Rybka and I. Honzík

Czech University of Life Sciences Prague, Faculty of Engineering, Department of Agricultural Machines, Kamýcká 129, CZ165 00 Praha 6 - Suchdol, Czech Republic
*Correspondence: hermanek@tf.czu.cz

Abstract:

The paper deals with monitoring the moisture content of hop cones and their parts (strigs and bracts) in PCHB 750 hop belt dryer. When drying hop cones, the critical point is the sufficient drying of the strig. These are therefore dried to a moisture content of 6 to 8%. This exact moisture provides a sufficient guarantee ensuring that the strig is dried up. On the other hand, bracts are dried up to such a level which makes pressing the hops impossible. Therefore, after drying, the bracts are remoistened. This is called hops conditioning. After conditioning the moisture content of hops is optimal, ranging between 8 and 11%. There is no doubt that drying or any further moistening does not benefit the hop cone.
During the experiment, the moisture content was determined regarding the whole hop cones as well as the bracts and strigs separately, the samples of which had been taken from the hops prior to entering the dryer, from different parts of belts in the dryer and subsequently before and after the conditioning. The moisture content was determined by means of Mettler HE53 moisture analyzer. After the bracts and strigs had been dried, we calculated their weight ratio which was approx. 90% of bracts and 10% of strigs. Based on this ratio the weighted average was calculated which corresponds to the moisture content of the whole hop cone.
The measured values indicate that the average moisture content of hops below 10% was already at the beginning of the third belt of the dryer. The hops had been unnecessarily overdried along the whole third belt. Another output refers to the moisture ratio of hop cones, bracts and strigs in different parts of the dryer. The obtained values will serve as a basis for the follow-up design of a device for monitoring the dryer parameters and its visualisation.

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859–865 A. Rybka, P. Heřmánek and I. Honzík
Theoretical analysis of the technological process of hop drying
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Theoretical analysis of the technological process of hop drying

A. Rybka*, P. Heřmánek and I. Honzík

Czech University of Life Sciences Prague, Faculty of Engineering, Department of Agricultural Machines, Kamýcká 129, CZ165 00 Praha 6 – Suchdol, Czech Republic
*Correspondence: rybka@tf.czu.cz

Abstract:

This article is aimed at the current questions concerning hop drying, a process which represents a significant part of energy consumption for hop producers. The water content drops during hop cone drying from the original approx. 80% of moisture to 8 or 10%. The drying medium is heated air, and the maximum drying temperatures range between 55 °C and 60 °C, remaining practically stable for the entire duration of drying. Hops are exposed to these temperatures for 6 to 8 hours. The current old and ageing belt dryers record large losses. Their modernisation and particularly new drying technologies need to derive from perfect knowledge of thermal characteristics of materials and drying devices. The drying process and the actual implementation necessarily depend on the knowledge of the entire process calculation that is why the paper introduction outlines simplified issues concerning a ‘theoretical dryer’ following the hx chart. An experimental measurement was carried out in an operating belt dryer. It included measurements of the drying medium thermal and moisture parameters and of the drying hop qualitative parameters. These drying parameters were monitored by means of continuously recording data loggers and of a laboratory analysis of the samples (hop moisture content, alpha bitter acids, Hop Storage Index). The drying process revealed that hops are practically dry (10 ± 2.0% of moisture content) already at the end of the second belt or possibly at the beginning of the third belt. It was also proven that hops are excessively dried (moisture content of 4 to 8%), adjusted to their final moisture of 8–10% through conditioning. Excessive drying results in considerate hop-cone shatter which makes the hop manipulation difficult during further processing, leading to larger losses of lupulin.

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713–719 P. Heřmánek, A. Rybka and I. Honzík
Experimental chamber dryer for drying hops at low temperatures
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Experimental chamber dryer for drying hops at low temperatures

P. Heřmánek*, A. Rybka and I. Honzík

Czech University of Life Sciences Prague, Faculty of Engineering, Department of Agricultural Machines, Kamýcká 129, CZ165 00 Praha 6 – Suchdol, Czech Republic
*Correspondence: hermanek@tf.czu.cz

Abstract:

Hop drying takes a significant part in growers’ costs of the final product processing. The current drying technology is based on drying at the drying air temperature of 55–60 °C for 6–9 hours to the final moisture content of about 10%. However, the process results in irreversible transformations and losses of, inter alia, heat labile substances contained in hops.
The experimental chamber dryer was tested at harvest in 2016. Assays hop drying were carried out at a temperature of the drying medium 40 °C. The research results in the form of an experimental new experimental chamber dryer will be used for testing of drying technologies at lower temperatures of the drying medium.
This is what will enable to preserve the quality of aroma as well as other characteristics of the components contained in hops.

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