Isolation of individual hop iso-α-acids stereoisomers by β-cyclodextrin

Khatib, Alfi; Wilson, Erica G.; Supardi, Moses; Verpoorte, Robert

doi:10.1016/j.foodchem.2009.06.011

Cited by 19 publications

(16 citation statements)

References 26 publications

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“…Separation of trans-iso-α-acids from cis-iso-α-acids, starting from the commercial isomerised hop extract, was successfully carried out by complex formation of the trans-iso-α-acids with β-cyclodextrin (β-CD, Acros Organics, Geel, Belgium), according to our in-house procedure based on Khatib et al 34,35 . This in-house procedure was performed on a pilot scale, permitting the quantitative dosage of trans-, respectively cis-iso-α-acids to fermented beer in mg/L amounts, and consisted of two successive complex formation steps with a saturated solution of β-CD in water (1.85 g/100 mL).…”

Section: Separation Of Trans-iso-α-acids From Cis-iso-α-acids In An Imentioning

confidence: 99%

“…1. HPLC separation of the Trans-extract, prepared according to our own isolation methodology based on selective removal of trans-isomers from the isomerised hop extract by treatment with β-cyclodextrin 34,35 , illustrating the purity of the extract containing 90% of trans-iso-α-acids. pH 2.80 with 85% phosphoric acid (Merck).…”

Section: Hplc Analysis Of Iso-α-acidsmentioning

confidence: 99%

“…Consequently, pure trans-respectively cis-isomers were required in large amounts for post-fermentation addition to finished beer. Separation of trans-from cis-iso-α-acids in a commercial isomerised hop extract was accomplished on a pilot scale by the formation of trans-iso-α-acids β-cyclodextrin inclusion complexes according to our in-house procedure based on Khatib et al 34,35 , permitting the quantitative dosage to beer in mg/L amounts (see Materials and Methods).…”

Section: Involvement Of Isohumulones In the Formation Of Volatile Aldmentioning

confidence: 99%

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

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Rouck

Cooman

et al. 2010

Journal of the Institute of Brewing

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In this paper, the involvement of iso-α-acids in the appearance of stale flavour in beer during storage was examined. Flavour instability upon storage, by far the most important quality problem of beer, may be caused by a multitude of reactions, in particular, the degradation of trans-iso-α-acids is pivotal. In order to gain improved understanding of the beer ageing process, the behaviour of the stereoisomers of the bitter acids was studied for the first time in pilot beers at particularly high and low proportions of the trans-iso-α-acids concentration relative to the cis-iso-α-acids concentration. Therefore, pure trans-respectively cis-isomers were required and obtained on a pilot scale by the separation of trans-iso-α-acids as β-cyclodextrin inclusion complexes from a commercial isomerised hop extract, permitting the quantitative dosage to beer in mg/L amounts. The relationship between the storage-induced degradation of these iso-α-acids in authentic beer samples and the increase in staling aldehydes, especially 2-methylpropanal, 2-methylbutanal and 3-methylbutanal, is the subject of further investigations. A remarkable increase in the relative concentration of cis-iso-α-acids was observed in the beers bittered with purified trans-iso-α-acids, which may be ascribed to partial conversion, i.e., reverse isomerisation, of trans-iso-α-acids via α-acids into cis-iso-α-acids. In spite of the trans-specific degradation observed during ageing, the decomposition of these bitter acids leading to volatile carbonyl compounds is of minor importance. Aldehyde formation as a function of forced ageing was irrespective of the mode of bittering, emphasising that malt quality and the brewing process itself are probably the most important factors regarding the flavour instability of beer.

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Section: Separation Of Trans-iso-α-acids From Cis-iso-α-acids In An Imentioning

confidence: 99%

Section: Hplc Analysis Of Iso-α-acidsmentioning

confidence: 99%

Section: Involvement Of Isohumulones In the Formation Of Volatile Aldmentioning

confidence: 99%

See 1 more Smart Citation

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

Clippeleer

Rouck

Cooman

et al. 2010

Journal of the Institute of Brewing

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“…It is also known that pure cis-isohumulones are more bitter than trans-isohumulones 21 . Just recently, purified cis-isohumulones were isolated for the first time 28 . Losses during the fermentation and storage of beer were shown to be higher for transisohumulones than for cis-isohumulones 8 , although there is little difference in polarity between the cis-and transisohumulones 20 .…”

Section: Introductionmentioning

confidence: 99%

Degradation of Iso-α-Acids During Wort Boiling

Kappler

Krahl

Geißinger

et al. 2010

Journal of the Institute of Brewing

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A detailed study on the degradation of iso-α-acids was conducted. Because of the complexity of the wort matrix and interfering interactions during real wort boiling, the investigation of degradation kinetics was performed in an aqueous solution. Degradation was investigated as a function of time (0-90 min), temperature (80-110°C), pH value (4-7), original gravity (10-18°P) and ion content of the water (0-500 ppm Ca 2+ and Mg 2+ ). After 90 min of boiling, over 20% of the dosed iso-α-acids could no longer be detected. A strong dependence of degradation could be shown due to high temperature, low pH, high original gravity and a high Mg 2+ content. The cis:trans ratio and co-iso-α-acid content did not change significantly. Losses of isohumulones could be lowered by reducing the temperature and original gravity, as well as by heightening the pH value. High amounts of Ca 2+ and Mg 2+ salts also led to an increase in degradation products. Solutions to decrease degradation and thereby possible improvements in sensory bitter quality are discussed.

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“…Moreover, the recognition ability of β‐CD derived from the selective incorporation of guests has found applications in many separation methods, mainly including selective extraction, chromatography, and inclusion separation, etc . Among all these methods, direct inclusion separation is one of the most used, as it provides a simple, low‐cost, and efficient procedure . Considering these merits, we have used the selective inclusion method for the isolation of several organic compounds with an aqueous solution of β‐CD .…”

Section: Introductionmentioning

confidence: 99%

Facile separation of cinnamyl acetate and cinnamaldehyde based on host–guest complexation with β‐cyclodextrin

Chai

Zheng

et al. 2018

Flavour & Fragrance J

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A selective inclusion of cinnamyl acetate (CAc) is observed during the complexation of CAc and cinnamaldehyde (CA) with β‐cyclodextrin (β‐CD) in aqueous solution. To demonstrate the potential application of β‐CD for the separation of CAc and CA, the preferential affinity of β‐CD for CAc over CA was studied from conformational and thermodynamic points of view. Determination of the complexation geometries, performed by 1H and 2D (XRD), confirmed the inclusion capacity of the β‐CD cavity for CAc and CA. From the stability constants measured by ultraviolet‐visible (UV–Vis) spectroscopy and thermodynamic parameters measured by isothermal titration microcalorimetry, it was found that compared to CA, hydrophobic and hydrogen bonding interactions jointly promote CAc to form a more stable β‐CD binding complex with 1:1 stoichiometry. Furthermore, the higher binding affinity of β‐CD for CAc (over CA) was investigated theoretically in terms of binding energy and inclusion geometries. The separation of the equimolar CAc–CA mixture was achieved by inclusion complexation in β‐CD aqueous solution. The effects of the experimental conditions, such as the polarity of the solvent and guest/host molar ratio, on separation performance were investigated. Under the optimized conditions, the selective inclusion procedure exhibited a CAc/CA separation factor of 3.5, which remained stable after five cycles, indicating that β‐CD is a highly reusable host material.

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Isolation of individual hop iso-α-acids stereoisomers by β-cyclodextrin

Cited by 19 publications

References 26 publications

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

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

Degradation of Iso-α-Acids During Wort Boiling

Facile separation of cinnamyl acetate and cinnamaldehyde based on host–guest complexation with β‐cyclodextrin

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