Applications of High-Performance Liquid Chromatography in the Control of Beer Bitterness

McMurrough, Ian; Cleary, K.; Murray, F. Jay

doi:10.1094/asbcj-44-0101

Cited by 6 publications

(11 citation statements)

References 17 publications

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“…At the lowest pH (pH 4.8), isomerisation is favoured in aqueous buffer, whereas at higher pH (pH 6.0 and especially pH 7.0), more satisfying and even very high isomerisation yields (>80%) are obtained in real wort. As found earlier by Verzele (1965), andMcMurrough et al (1986), in real wort, there appears to be an increase in isomerisation yield with increasing pH. However, in aqueous buffer medium, our results indicate that isomerisation yields obtained at the lower pH values (pH 4.8 up to pH 5.5) remain similar.…”

Section: Hplc Analysis Of A-acids and Iso-a-acidssupporting

confidence: 85%

“…The mechanism of a-acids isomerisation into iso-a-acids (Verzele & De Keukeleire, 1991). Cleary, and Murray (1986). In addition, these authors showed that the isomerisation yield decreases with increasing wort gravity and that approx.…”

Section: Introductionmentioning

confidence: 94%

“…According to Laws et al (1972), McMurrough et al (1986 and Benitez et al (1997) wort original gravity is an important factor that influences final a-acids utilisation, i.e., a high gravity wort will promote losses of iso-a-acids, resulting in lower beer bitterness.…”

Section: Effect Of Wort Gravitymentioning

confidence: 99%

See 2 more Smart Citations

Potential impact of medium characteristics on the isomerisation of hop α-acids in wort and buffer model systems

2010

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Section: Hplc Analysis Of A-acids and Iso-a-acidssupporting

confidence: 85%

Section: Introductionmentioning

confidence: 94%

See 1 more Smart Citation

Potential impact of medium characteristics on the isomerisation of hop α-acids in wort and buffer model systems

2010

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“…Several methods based on high performance liquid chromatography (HPLC) have been proposed for the quantitative determination of iso-α-acids and α-acids in hopped wort and beer 5,13,21,22,28,35 . The state-of-the-art of HPLC of hop and beer bitter acids is largely derived from the earlier work of the research group of Verzele and De Keukeleire 34 .…”

Section: Evaluation Of Hplc Methodologymentioning

confidence: 99%

Enhanced Quantitative Extraction and HPLC Determination of Hop and Beer Bitter Acids

Jaskula¹,

Goiris²,

Rouck³

et al. 2007

Journal of the Institute of Brewing

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A pleasant and consistent bitterness is an essential flavour attribute of beer. Hop-derived iso-α-acids are largely responsible for beer bitterness and accurate determination of these primary flavour compounds is very important in relation to quality control. The most widely used way to determine beer bitterness is based on spectrophotometry, measuring the absorbance of an iso-octane extract of acidified beer. However, this approach is far from specific as it measures all of the extracted compounds, including non-bittering principles. For that particular reason, High Performance Liquid Chromatography (HPLC) is increasingly applied for the quantitative determination of hop-derived iso-α-acids and, if present, reduced iso-α-acids. However, to obtain accurate data on beer bitterness profiles, both quantitative sample preparation and state-of-the-art HPLC are essential. In this paper, several extraction procedures based on solid phase extraction (SPE) and liquid-liquid extraction (LLE), respectively, were evaluated and an optimised extraction methodology using H 3 PO 4 for sample acidification prior to extraction is presented. The proposed extraction/HPLC methodology allows for the quantitative recovery and analysis of hop-derived beer bitterness.

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“…McMurrough et al (4) conducted wort-boiling experiments in both a model system (glass reaction vessel with a reflux condenser) and a high-gravity wort heated in a pressurized kettle. The model system consisted of a KH 2 PO 4 buffer with initial concentrations of approximately 300-330 ppm alpha acids and was continuously stirred during heating.…”

Section: Pertinent Literaturementioning

confidence: 99%

Isomerization and Degradation Kinetics of Hop (Humulus lupulus) Acids in a Model Wort-Boiling System

Malowicki

Shellhammer

2005

J. Agric. Food Chem.

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The rate of isomerization of alpha acids to iso-alpha acids (the compounds contributing bitter taste to beer) was determined across a range of temperatures (90-130 degrees C) to characterize the rate at which iso-alpha acids are formed during kettle boiling. Multiple 12 mL stainless steel vessels were utilized to heat samples (alpha acids in a pH 5.2 buffered aqueous solution) at given temperatures, for varying lengths of time. Concentrations of alpha acids and iso-alpha acids were quantified by high-pressure liquid chromatography (HPLC). The isomerization reaction was found to be first order, with reaction rate varying as a function of temperature. Rate constants were experimentally determined to be k1 = (7.9 x 10(11)) e(-11858/T) for the isomerization reaction of alpha acids to iso-alpha acids, and k2 = (4.1 x 10(12)) e(-12994/T) for the subsequent loss of iso-alpha acids to uncharacterized degradation products. Activation energy was experimentally determined to be 98.6 kJ per mole for isomerization, and 108.0 kJ per mole for degradation. Losses of iso-alpha acids to degradation products were pronounced for cases in which boiling was continued beyond two half-lives of alpha-acid concentration.

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Applications of High-Performance Liquid Chromatography in the Control of Beer Bitterness

Cited by 6 publications

References 17 publications

Potential impact of medium characteristics on the isomerisation of hop α-acids in wort and buffer model systems

Potential impact of medium characteristics on the isomerisation of hop α-acids in wort and buffer model systems

Enhanced Quantitative Extraction and HPLC Determination of Hop and Beer Bitter Acids

Isomerization and Degradation Kinetics of Hop (Humulus lupulus) Acids in a Model Wort-Boiling System

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