Latest findings on bitter substances in coffee
Why caffeine is not the sole contributor to bitterness

Date:
June 17, 2020
Source:
Leibniz-Institut fu"r Lebensmittel-Systembiologie an der TU Mu"nchen
Summary:
Coffee is very popular around the world despite or perhaps because
of its bitter taste. Compounds contained in the coffee such as
caffeine contribute to the bitterness to varying degrees. A recent
study provides new insights into the molecular interactions between
bitter substances and bitter receptors. This is of relevance not
only for taste perception.



FULL STORY ========================================================================== Coffee is very popular around the world despite or perhaps because of
its bitter taste. Compounds contained in the coffee such as caffeine
contribute to the bitterness to varying degrees. A recent study conducted
by the Leibniz- Institute for Food Systems Biology and the Technical
University of Munich (TUM) provides new insights into the molecular interactions between bitter substances and bitter receptors. This is of relevance not only for taste perception.


========================================================================== Caffeine is surely the best-known bitter coffee constituent. However, this stimulating substance is not solely responsible for the bitter taste of
the beverage. The latest findings from a study conducted by the Freising
team of scientists confirm this. Using a cell-based testing system -- a
type of artificial tongue -- and docking analyses, the team investigated
five different bitter coffee constituents. The tests included the bitter substance mozambioside identified in Arabica beans, its roast product bengalensol, and the well-known coffee compounds cafestol, kahweol,
and caffeine.

Based on the results of their study, the research team assumes that
mainly two of the 25 human bitter taste receptors respond to the coffee's constituents.

Whereas a relatively high concentration of caffeine is necessary to
stimulate the receptors TAS2R46 and TAS2R43, considerably smaller amounts
of the other four substances are needed. The caffeine concentration
required to activate the bitter taste receptor TAS2R43 to the same
degree as mozambioside or bengalensol was about 30 and 300 times higher, respectively, says lead author Tatjana Lang from the Leibniz-Institute
for Food Systems Biology.

Bitter substance reduces bitter taste? Further studies conducted
by the researchers suggest that the bitter substances contained in
coffee interact with each other. These studies showed that kahweol and mozambioside exhibit similar binding properties for the bitter taste
receptor TAS2R43. Compared to mozambioside, however, kahweol receptor activation was relatively weak and, depending on the dose, was capable
of inhibiting the mozambioside-induced activation of the bitter taste
receptor.

"We therefore assume that kahweol can reduce the bitter taste elicited by TAS2R43 by suppressing more effective bitter substances at the receptor,"
says principal investigator Maik Behrens, who is head of the research
group Taste Systems Reception & Biosignals at the Leibniz-Institute.

Behrens adds that this effect could play a role in coffee preparations
that do not include a filtering step like espresso or Turkish coffee,
which are beverages that contain kahweol.

Bitter receptor affects gastric acid secretion Behrens says the study
results are exciting from another perspective as well, adding that: "All
of our findings indicate that bitter coffee substances quite specifically activate two of the 25 bitter taste receptors. We furthermore know that
both types of receptors are present not only in taste cells. TAS2R43 is
also present in the stomach and in conjunction with caffeine plays a role
in the regulation of gastric acid secretion. The question now arises as
to how coffee constituents like bengalensol, which activate the receptor
with much higher potency, might be involved in this regulatory process."
It is also interesting that many people do not possess the bitter taste receptor TAS2R43 due to a genetic variation. This could explain the
differences in individual coffee taste perception or its tolerability
says Veronika Somoza, director of the Leibniz-Institute for Systems
Biology. She adds that much more research is needed to elucidate the
complex interaction of bitter substances, bitter receptors, and their
effects on the human body.


========================================================================== Story Source: Materials provided by Leibniz-Institut_fu"r_Lebensmittel-Systembiologie_an_der
TU_Mu"nchen. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Tatjana Lang, Roman Lang, Antonella Di Pizio, Verena Karolin
Mittermeier,
Verena Schlagbauer, Thomas Hofmann, Maik Behrens. Numerous Compounds
Orchestrate Coffee's Bitterness. Journal of Agricultural and Food
Chemistry, 2020; 68 (24): 6692 DOI: 10.1021/acs.jafc.0c01373 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/06/200617121445.htm

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