Three TAS2R Bitter Taste Receptors Mediate the Psychophysical Responses to Bitter Compounds of Hops (Humulus lupulus L.) and Beer
- 1k Downloads
In order to study the role of different haplotypes of taste receptor genes in food choice, it is necessary to first identify the cognate hTAS2R bitter taste receptors for the key bitter compounds in food products of our daily diet. In order to identify the candidate receptors mediating the bitter taste of hop-containing beverages such as beer, we transiently transfected plasmids encoding the 25 human TAS2Rs into human embryonic kidney 293T cells, stably expressing the chimeric G-protein G16gust44. Thereby, we coupled the activation of hTAS2R receptors to the release of Ca2+ from intracellular stores. The transfected cells were loaded with a calcium-sensitive fluorescence dye and challenged by 15 hop-derived compounds, including α-acids, β-acids, trans/cis-iso-α-acids, isoxanthohumol, xanthohumol, and 8-prenylnaringenin. Depending on their chemical structure, all these compounds activated various combinations of the three bitter taste receptors hTAS2R1, hTAS2R14, and hTAS2R40 with distinct threshold concentrations and EC50 values. Notably, this is the first time that an agonist for hTAS2R40 is reported. The threshold concentrations and EC50 values obtained from the taste receptor assays were much lower than those determined by human psychophysical experiments, even though the rank order of potency for the various compounds was similar in both experiments. Thus, the subjects perceived the bitterness of the investigated compounds at higher concentrations than those predicted by the results of the in vitro experiments. These differences were shown to be due, at least in part, to interactions of the bitter substances with the oral mucosa.
KeywordsBeer Hop Iso-alpha Acids hTAS2R hTAS2R1 hTAS2R14 hTAS2R40 Bitter Taste Oral Mucosa
We are grateful to Elke Chudoba for her excellent technical assistance and to the Hallertauer Hopfenveredelungsgesellschaft mbH (Mainburg, Germany) for providing hop samples. This work was supported by a grant from the German Science Foundation to WM (DFG, ME 1024/2-3) as well as from the Fond der Chemischen Industrie to TH.
- Anonymous (2007) DIN EN ISO 4120—Sensory analysis—methodology—triangle test (ISO 4120:2004). German Version (EN ISO 4120:2007)Google Scholar
- Fritsch A, Shellhammer TH (2007) Alpha-acids do not contribute bitterness to lager beer. J Am Soc Brew Chem 65:26–28Google Scholar
- Fritsch H, Biendl M, Stephan A, Stettner G, Methner FJ (2005) Sensory characterisation of xanthohumol and isoxanthohumol. 30th International Congress European Brewery Convention, PragueGoogle Scholar
- Hughes PS, Simpson WJ (1994). Sensory impact of hop-derived compounds. Monograph European Brewing Convention, vol. 22 Leidin, pp. 128–140 Google Scholar
- Hughes PS, Simpson WJ (1996) Bitterness of congeners and stereoisomers of hop-derived bitter acids found in beer. J Am Soc Brew Chem 54:234–237Google Scholar
- Kowaka M, Kokubo E (1976) Composition of bitter substances of hops and characteristics of beer bitterness. J Am Soc Brew Chem 35:16–21Google Scholar
- Ueda T, Ugawa S, Yamamura H, Imaizumi Y, Shimada S (2003) Functional interaction between T2R taste receptors and G-protein alpha subunits expressed in taste receptor cells. J Neurosci 23:7376–7380Google Scholar
- Verzele M (1970) Non-bitter hop contributions to beer. Proc Am Soc Brew Chem, 63–67Google Scholar
- Verzele M, Jansen HE, Ferdinandus A (1970) Organoleptic trials with hop bitter substances. J Inst Brew 76:25–28Google Scholar
- Weiss A, Schönberger C, Mitter W, Biendl M, Back W, Krottenthaler M (2002) Sensory and analytical characterisation of reduced, isomerised hop extracts and their influence and use in beer. J Inst Brew 108:236–242Google Scholar