Photometric Constants of Hop Bitter Acids

Claus, H.; Dyck, J. Van; Verzele, M.

doi:10.1002/j.2050-0416.1978.tb03874.x

Cited by 19 publications

(6 citation statements)

References 4 publications

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“…Because humulones may contribute to the BU value, but are not bitter, they may affect the BU's ability to accurately predict bitterness intensity. 13,23 As previously stated, isohumulones are the primary source of bitter taste in beer. They are isomers of hop-derived humulones, which are transformed with heat and time via a first order reaction that is temperature-dependent.…”

Section: ■ Results and Discussionmentioning

confidence: 93%

“…By 1968, the BU was internationally recognized as a standard method by the American Society of Brewing Chemists (ASBC) and the European Brewery Convention . In addition to measuring isohumulones, other ultraviolet-absorbing compounds may influence the BU value. ,, The inclusion of nonisohumulone substances in the BU assay presents a challenge to brewers, particularly when using this technique to evaluate beer styles that have been heavily hopped. , …”

Section: Introductionmentioning

confidence: 82%

“…22 In addition to measuring isohumulones, other ultraviolet-absorbing compounds may influence the BU value. 4,20,23 The inclusion of nonisohumulone substances in the BU assay presents a challenge to brewers, particularly when using this technique to evaluate beer styles that have been heavily hopped. 4,10 Advances in instrumentation now allow for the rapid and easy measurement of isohumulones in beer using highperformance liquid chromatography (HPLC).…”

Section: ■ Introductionmentioning

confidence: 99%

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Evaluation of Nonvolatile Chemistry Affecting Sensory Bitterness Intensity of Highly Hopped Beers

Hahn

Lafontaine

Pereira

et al. 2018

J. Agric. Food Chem.

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The range of different nonvolatile constituents extracted from hops in highly hopped beers suggests that isohumulones may not be the sole contributor to beers' bitterness. Among brewers producing hop-forward beer styles, there is concern that the bitterness unit (BU) is no longer an accurate predictor of beer bitterness. This study examined factors within the beer matrix that influence sensory bitterness perception in highly hopped beers. Over 120 commercial beers were evaluated using sensory and instrumental techniques. Chemical analysis consisted of the BU via spectrophotometry, hop acids via high-performance liquid chromatography, total polyphenols via spectrophotometry, and alcohol content plus real extract via an Alcolyzer. Sensory analysis was conducted over two studies, and the beers' overall bitterness intensities were rated using a 0-20 scale. This study identified that the BU measurement predicts sensory bitterness with a nonlinear response, and it proposed an alternative approach to predicting bitterness based on isohumulones, humulinones, and ethanol concentrations. The study also revealed the importance of oxidized hop acids, humulinones, as a significant contributor to beer bitterness intensity.

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Section: ■ Results and Discussionmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 82%

Section: ■ Introductionmentioning

confidence: 99%

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Evaluation of Nonvolatile Chemistry Affecting Sensory Bitterness Intensity of Highly Hopped Beers

Hahn

Lafontaine

Pereira

et al. 2018

J. Agric. Food Chem.

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“…The laboratory analyses monitored the moisture content of all hop samples that was subsequently compared with the drying medium relative humidity measured by means of data loggers and fixed sensors in the dryer. At the same time, the values of HSI, content of alpha and beta bitter acids and DMX in hop cones were determined (Claus et al 1978;Green, Osborne 1993;Weihrauch at al. 2010).…”

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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“…Their structures have been verified by elemental analysis 23,24 , 1 H and 13 C NMR 17,23,24 , chiroptical methods 23,24 , GC-MS 16,24 , MS 9,11,21 , UV 4,11,23 and HPLC 2,5,8,9,21,23 . The preparation of pure iso-␣-acid from hop-derived extracts has also been described by Hughes 12 .…”

Section: Introductionmentioning

confidence: 92%

Liquid Chromatography-Diode Array and Electrospray High-Accuracy Mass Spectrometry of Iso-α-Acids in DCHA-Iso Standard and Beer

Hofta

Dostálek

Sýkora

2007

Journal of the Institute of Brewing

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Excellent liquid chromatographic (LC) separation of cis/trans stereoisomers of iso-␣-acids has been achieved with reversedphase sorbent XTerra MS C18. An isocratic alkaline mobile phase, consisting of a mixture of 5 mmol l -1 ammonium acetate (pH 8)-acetonitrile-methanol, 62:21:17 (v/v/v), was used. In the DCHA-Iso international calibration standard trans-isoposthumulone was identified combining photo diode array (PDA) spectra and electrospray high-accuracy mass spectrometric (MS) data. Moreover, the molecular mass of two degradation products resulting from the in-solution storage of the DCHA-Iso standard was determined. The presence of trans and cis isomers of isoposthumulone, isocohumulone, isoadhumulone and iso-n-humulone in beer samples was confirmed. The trans isomers of iso-␣-acids showed characteristic and reproducibly slightly different ultraviolet absorbance spectra with respect to cis isomers.

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Photometric Constants of Hop Bitter Acids

Abstract: The specific extinction values for the most important bitter acids are determined.

Cited by 19 publications

References 4 publications

Evaluation of Nonvolatile Chemistry Affecting Sensory Bitterness Intensity of Highly Hopped Beers

Evaluation of Nonvolatile Chemistry Affecting Sensory Bitterness Intensity of Highly Hopped Beers

Parameters of the drying medium and dried hops in belt dryer

Liquid Chromatography-Diode Array and Electrospray High-Accuracy Mass Spectrometry of Iso-α-Acids in DCHA-Iso Standard and Beer

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