Bouquet with a petrol note
A slight petrol aroma can certainly contribute to the complexity of a Riesling, but it should not be too dominant. A research team has now been able to clarify how people perceive this scent.
Climate change does not stop at vines. Too much sun means that the bouquet of German Riesling wines is increasingly characterized by a petrol note that not everyone likes. A research team from the Leibniz Institute for Food Systems Biology at the Technical University of Munich has now identified the human olfactory receptor responsible for the perception of this particular aroma note for the first time.
The grapevine(Vitis vinifera) is one of the most economically important fruit plants, with Riesling being one of the classic grape varieties. The bouquet of this white wine is characterized by floral, fruity and honey-like nuances, accompanied by a more or less pronounced petrol note. The latter is due to an odorant with the chemical name 1,1,6-trimethyl-1,2-dihydronaphthalene (TDN). Low and moderate concentrations of this odorant contribute to the complexity of the wine bouquet. However, wines with higher levels are often rejected by local consumers.
Higher UV exposure increases the petrol note
Compared to German Riesling, Riesling wines from South Africa or Australia generally have significantly higher concentrations of the odor component. The reason for this appears to be the higher UV exposure of the grapes in the southern hemisphere, which leads to increased carotenoid production in the plants. Like pigments in human skin, these natural colorants serve as sun protection. However, they are also molecular precursors of the odorant TDN.
Various studies indicate that the odor perception threshold of the olfactory substance, which is reminiscent of petroleum and kerosene, is between approx. 2 and 20 micrograms per liter. Nevertheless, the human olfactory receptor for the fragrance was previously unknown. As the research team led by Dietmar Krautwurst has now shown for the first time, it is the OR8H1 receptor.
Receptor with a specific recognition profile
The team identified the odorant receptor using bidirectional receptor screening. Using a cellular test system, they examined which of a total of 766 human odorant receptor variants react to the petroleum note. The OR8H1 receptor was the only one to respond to physiologically significant concentrations of the kerosene-like odorant. The team then investigated whether the identified receptor also reacted to other food-relevant odorants. Of the 180 substances tested, only seven, predominantly aromatic compounds, were able to significantly activate the receptor.
"The recognition spectrum of the receptor is therefore very specific. However, it complements the spectrum of another olfactory receptor that recognizes a very broad range of food-relevant odorants," reports first author Franziska Haag. Study leader Dietmar Krautwurst adds: "Our new findings help us to better understand the molecular mechanisms that contribute to the overall olfactory picture of a food, for example the complex bouquet of a wine."
The researchers assume that a deeper understanding of the molecular background will lead to the development of new sensor technologies for food aromas in the long term. These could then be used to better control not only the petrol note in wines, but also the occurrence of (off) flavors in other foods.
Note: This article has been translated using a computer system without human intervention. LUMITOS offers these automatic translations to present a wider range of current news. Since this article has been translated with automatic translation, it is possible that it contains errors in vocabulary, syntax or grammar. The original article in German can be found here.
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