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

Abstract

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.

Influence of the Hopping Technology on the Storage-induced Appearance of Staling Aldehydes in Beer

“…Bitter acids were isolated from beer by liquid-liquid extraction, based on the modified IoB method 9.16 29 , as described by Jaskula et al 30 Degassed beer (100 mL) was acidified with 5 mL of 12 M H 3 PO 4 (Merck, Darmstadt, Germany) and partitioned in a separating funnel with 250 mL of iso-octane (Acros Organics, Geel, Belgium). After phase separation, the iso-octane layer (125 mL) was collected, and the solvent was removed under reduced pressure at 30°C.…”

“…Initially, quantitative headspace SPME GC-MS profiling of 2-methylpropanal, 2-methylbutanal and 3-methylbutanal was performed on the fresh and forced aged (30,60,90,120 and 150 days at 30°C in the dark) beer samples Iso-A, Cis-A, Trans-A, and Blank-A, all derived from the first basic brew obtained with malt A (Table I). The observations regarding the formation of these aldehydes upon ageing as a function of the different bittering applied, are summarised in Table III.…”

“…According to these authors, the development of aldehydes was suppressed by decreasing the levels of isohumulones in beer. In order to identify other critical factors related to the flavour stability of beer in terms of the formation of these branched aldehydes, quantitative headspace SPME GC-MS profiling of 2-methylpropanal, 2-methylbutanal and 3-methylbutanal was thereupon performed on the fresh and forced aged (30,60,90,120 and 150 days at 30°C in the dark) identically brewed and bittered beer samples Iso-B, Cis-B, Trans-B, and Blank-B, derived from the basic brew obtained with malt B, of which the results are summarised in Table IV. Formation of these aldehydes upon ageing as a function of the different bittering applied, as well as the malt used for beer production, is depicted in Fig.…”

Analytical-Sensory Determination of Potential Flavour Deficiencies of Light Beers

“…Extraction of the bitter acids from beer was carried out according to Jaskula et al 11 . HPLC analysis of iso-α-acids was performed on a Hitachi liquid chromatograph (Merck, Darmstadt, Germany) which consists of a programmable HPLC pump (L-7100) with a quaternary low pressure gradient system, a diode array detector (L-7450A), an interface module (D-7000), a solvent degasser (L-7612), an autosampler (L-7200), a Compaq Deskpro 2000 (Merck D-7000 Rev.…”

Analytical and Sensory Assessment of Hoppy Aroma and Bitterness of Conventionally Hopped and Advanced Hopped Pilsner Beers

“…; Alltech Associates, Deerfield, USA). A dicyclohexylamine-iso-α-acids ICS-I1 complex (66.5% (w/w) iso-α-acids) (Labor Veritas, Zürich, Switzerland) was used for quantitative determination of iso-α-acids (additional details on HPLC analysis of iso-α-acids are given in the references 4,17 ).…”