Iso-α-acids, bitterness and loss of beer quality during storage

Caballero, Isabel; Blanco, Carlos A.; Porras, María Eugenia de

doi:10.1016/j.tifs.2012.01.001

Cited by 89 publications

(65 citation statements)

References 63 publications

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“…The engineered strains in this study also provide a starting point for the functional identification of other components involved in the bitter acid pathway. Among these, the elucidation of the enzyme responsible for the last oxidation step in the a-bitter acid pathway has the high priority due to its critical role in flavoring beer (Caballero et al, 2012). Several P450s and monooxygenase genes have been identified from the TrichOME database, and together with the fact that DD-acylphloroglucinol (the proposed precursor for the reaction) is produced in our engineered yeast, these hold promise for the completion of the whole jigsaw puzzle of the complete bitter acid pathway.…”

Section: Resultsmentioning

confidence: 99%

A Heteromeric Membrane-Bound Prenyltransferase Complex from Hop Catalyzes Three Sequential Aromatic Prenylations in the Bitter Acid Pathway

et al. 2015

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Bitter acids (a and b types) account for more than 30% of the fresh weight of hop (Humulus lupulus) glandular trichomes and are well known for their contribution to the bitter taste of beer. These multiprenylated chemicals also show diverse biological activities, some of which have potential benefits to human health. The bitter acid biosynthetic pathway has been investigated extensively, and the genes for the early steps of bitter acid synthesis have been cloned and functionally characterized. However, little is known about the enzyme(s) that catalyze three sequential prenylation steps in the b-bitter acid pathway. Here, we employed a yeast (Saccharomyces cerevisiae) system for the functional identification of aromatic prenyltransferase (PT) genes. Two PT genes (HlPT1L and HlPT2) obtained from a hop trichome-specific complementary DNA library were functionally characterized using this yeast system. Coexpression of codon-optimized PT1L and PT2 in yeast, together with upstream genes, led to the production of bitter acids, but no bitter acids were detected when either of the PT genes was expressed by itself. Stepwise mutation of the aspartate-rich motifs in PT1L and PT2 further revealed the prenylation sequence of these two enzymes in b-bitter acid biosynthesis: PT1L catalyzed only the first prenylation step, and PT2 catalyzed the two subsequent prenylation steps. A metabolon formed through interactions between PT1L and PT2 was demonstrated using a yeast two-hybrid system, reciprocal coimmunoprecipitation, and in vitro biochemical assays. These results provide direct evidence of the involvement of a functional metabolon of membrane-bound prenyltransferases in bitter acid biosynthesis in hop.

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Section: Resultsmentioning

confidence: 99%

A Heteromeric Membrane-Bound Prenyltransferase Complex from Hop Catalyzes Three Sequential Aromatic Prenylations in the Bitter Acid Pathway

et al. 2015

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“…Several compounds have been pointed out as key agents of beer sensory changes and suggested as deterioration markers during ageing, in particular diacetyl [5], acetaldehyde and ethyl acetate [6], (E)-2-nonenal [7], Iso-α-acids [8], riboflavin and amino acids [9] and 5-hydroxymethylfurfural [10]. However, the evaluation of beer shelf life should be more comprehensive and take into account the heterogeneity of chemical volatile groups presented in beer, which can either individually or simultaneously, influence the beer stale flavor in a synergistic or antagonistic sense [11].…”

Section: Introductionmentioning

confidence: 99%

Chemometric analysis of the volatile fraction evolution of Portuguese beer under shelf storage conditions

Rendall

Reis

Pereira

et al. 2015

Chemometrics and Intelligent Laboratory Systems

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“…Finally, iso-α-acids are directly correlated with beer bitterness and also have significant UV spectra; they occur in beer in concentrations varying between 15 and 100 mg/L. [41] Thus, the use of chemometric techniques like PCR and ANN was assessed to find suitable correlations between the beer UV-Vis spectrum and its corresponding quality attributes.…”

Section: Uv-vis Absorption Spectra Of Beer Samplesmentioning

confidence: 99%

Rapid monitoring of beer-quality attributes based on UV-Vis spectral data

Oliveira

Filho

Rocha

et al. 2017

International Journal of Food Properties

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This work aimed to determinate eight beer properties using UV-Vis spectra in combination with principal component regression (PCR) or artificial neural network (ANN) models. A statistical experimental design was performed to generate the calibration data. First, principal component analysis (PCA) was applied to the original spectral data, and the scores in significant PCs were utilized to calibrate both models. PCR showed poor correlation for beer parameters (R 2 < 0.61). The ANNs showed satisfactory correlations (R 2 = 0.74-0.92) and low relative error considering a variable range (E r < 9%) for most of the beer-quality attributes, but vicinal diketones (R 2 = 0.56, E r = 16.69%). Once implemented, this method would be fast and low cost. ARTICLE HISTORY

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Iso-α-acids, bitterness and loss of beer quality during storage

Cited by 89 publications

References 63 publications

A Heteromeric Membrane-Bound Prenyltransferase Complex from Hop Catalyzes Three Sequential Aromatic Prenylations in the Bitter Acid Pathway

A Heteromeric Membrane-Bound Prenyltransferase Complex from Hop Catalyzes Three Sequential Aromatic Prenylations in the Bitter Acid Pathway

Chemometric analysis of the volatile fraction evolution of Portuguese beer under shelf storage conditions

Rapid monitoring of beer-quality attributes based on UV-Vis spectral data

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