Equilibrium moisture content of hops

Henderson, Sylvia

doi:10.1016/0021-8634(73)90032-2

Cited by 12 publications

(13 citation statements)

References 3 publications

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“…The resulting moisture content is expressed as a weight percentage. Dried hops generally contain 10 ± 2.0% of water (Henderson, Miller 1972;Henderson 1973).…”

Section: Methodsmentioning

confidence: 99%

Parameters of the drying medium and dried hops in belt dryer

Rybka¹,

Heřmánek²,

Honzík³

et al. 2017

Res. Agric. Eng.

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Rybka A., Heřmánek P., Honzík I., Krofta K. (2017): Parameters of the drying medium and dried hops in belt dryer. Res. Agr. Eng., 63 (Special Issue): S24-S32.An important factor in hop growing is the process of drying. For this purpose belt dryers with follow-up conditioning are the most widespread but they are not ideal. In this respect, an analysis of the drying process was carried out in the belt dryer of Agrospol Velká Bystřice Co., Ltd. for the 'Saaz' hop variety. Drying parameters were monitored by means of fixed sensors, continuously sensing data loggers and samples taken for laboratory analysis (hop moisture, alpha and beta bitter acids, Hop Storage Index (HIS). The process of drying showed that hops are practically dry (10 ± 2.0% of moisture) already at the end of the second belt or possibly at the beginning of the third belt. It was also proved that hops are over-dried (moisture of 4 to 8%) and then they are adjusted by conditioning to the final moisture content of 8-10%. Excessive drying leads to cone disintegration, which makes any manipulation with hops for purposes of further processing difficult and results in greater losses of lupulin. The current state in the field of technology of hop drying and conditioning is not ideal. This refers to both operating costs and qualitative features of the final product. In belt dryers prevailing so far, following stationary picking lines, their drying process is directly linked to the continuous process of harvest. In belt dryers hop cones are dried at a drying air temperature of 55-60 o C for 6-8 h coming from original 75-85% of moisture to final 8-10% prior to conditioning. Bracts themselves, however, have moisture content of only 5-6%, while strigs may have a moisture content of up to 30%. Percentage of strig weight to the total cone weight (6-12%) has a great effect on subsequent moisture permeability during the conditioning of hop cones (Kořen et al. 2008). Controlled conditioning requires roughly up to a 1/3 of the total energy requirements needed for hop growing (Doe, Menary 1979). Stability of alpha bitter acids, being the key hop substance from the point of view of brewing technology, is sufficient at drying temperatures reaching up to 60°C. However, for some heat-labile substances the drying temperatures between 50 and 60°C in the final stage of drying are too high. They lead to irreversible transformations and losses. Such substances are for instance hop essential oils that are contained in the amount of 0.5-3.5%, depending on hop variety (Hofmann et al. 2013;Kumhála et al. 2013). The pilot studies showed a decrease of 15 to 25% of the overall content of essential oils present in the hops prior to drying at the current drying conditions (Kieninger, Forster 1973;Kirchmeier at al. 2005). Besides this amount, the sensory profile changes too, due to a loss of the more volatile components. With special aroma hop varieties, so called "flavour hops", whose 25Vol. 63, 2017, Special Issue: S24-S32 Res. Agr. Eng.doi: 10.17221/35/2017-RAE content and ...

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“…The resulting moisture content is expressed as a weight percentage. Dried hops generally contain 10 ± 2.0% of water (Henderson, Miller 1972;Henderson 1973).…”

Section: Methodsmentioning

confidence: 99%

Parameters of the drying medium and dried hops in belt dryer

Rybka¹,

Heřmánek²,

Honzík³

et al. 2017

Res. Agric. Eng.

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“…While this has increased the availability of hops globally, brewers lose a large amount of essential oils because of evaporation as the hops must be dried to 10% moisture content before being packaged to prevent spoilage. 4 This has shaped a seasonal tradition in Sonoma County of producing “wet hopped” beers where brewers work with growers to make beer using hops freshly harvested from the bine. With the utilization of fresh hops in the brewing industry, an accurate method for testing α-acids with considerations of a fresh cone’s higher moisture content was needed.…”

Section: Introductionmentioning

confidence: 99%

“…Consumers also have the option of choosing between packaged hops in the natural cone state or a condensed pelletized form. While this has increased the availability of hops globally, brewers lose a large amount of essential oils because of evaporation as the hops must be dried to 10% moisture content before being packaged to prevent spoilage . This has shaped a seasonal tradition in Sonoma County of producing “wet hopped” beers where brewers work with growers to make beer using hops freshly harvested from the bine.…”

Section: Introductionmentioning

confidence: 99%

Quantification of α-Acids in Fresh Hops by Reverse-Phase High-Performance Liquid Chromatography

et al. 2019

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This publication describes a method for the quantification by high-performance liquid chromatography (HPLC) of resinous compounds known as α-acids found in freshly harvested, unprocessed hops. This method provides consistent, efficient, and accurate results as well as the theories and rationale involved in HPLC method development. A system of quality checks was utilized as well as the validation of numerous developmental variables. By starting with a theoretical approach in preparation, extraction, and instrumental techniques and then further developing these practices by experimentation, a reproducible method was developed. Following the validation, fresh cascade hops grown in Sonoma County were analyzed during the 2017 harvest season and found to be within the predicted range specific to this cultivar. This method encompasses the techniques necessary to analyze fresh or dried hops, considering variability between different laboratories.

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“…Conventional drying at a temperature of 55-60°C results in irreversible transformations and losses of essential oils that reduce the product quality. Pilot studies have shown that under the current drying temperatures of 55-60°C, the total amount of essential oils is reduced by 15% to 25% compared to conditions before drying (Henderson 1973). During wort boiling, a major part of essential oils evaporates from the brew kettle with water steam.…”

mentioning

confidence: 99%

Effect of drying temperature on the content and composition of hop oils

Rybka¹,

Krofta²,

Heřmánek³

et al. 2018

PLANT SOIL ENVIRON

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In terms of content, the paper is aimed at analysing and comparing the quality of fresh green hops and hops dried at two drying temperatures – 55°C (in the traditional manner) and 40°C (using the so-called gentle drying), regarding the maximum preservation of hop essential oils. Comparative experiments were carried out in an experimental chamber dryer with two Czech hop cultivars Saaz and Harmonie. The moisture content of hops at the beginning of drying was 75% and at the end of drying it was 9–10%. By lowering the drying temperature from 55°C to 40°C, the drying time in cv. Saaz prolonged from 8 to 10 h and for the cv. Harmonie from 9 h to 12 h. Compared to fresh hops, the amount of hop oils decreased by 10% when dried at 40°C and by 36% (cv. Saaz) and 43% (cv. Harmonie) when dried at 55°C. These losses can be considered significant, especially for hops intended for late and dry beer hopping. However, by drying the hops at different temperatures, the ratios between various components of the essential oils and thus also their sensory character remained approximately unchanged. Due to the reduced amount of essential oils, the drying effect reduces the intensity of hop aroma depending on the drying temperature.

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Equilibrium moisture content of hops

Cited by 12 publications

References 3 publications

Parameters of the drying medium and dried hops in belt dryer

Parameters of the drying medium and dried hops in belt dryer

Quantification of α-Acids in Fresh Hops by Reverse-Phase High-Performance Liquid Chromatography

Effect of drying temperature on the content and composition of hop oils

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