New insights into the perception of coffee taste - genetic predisposition plays a role

Why does coffee taste more bitter to some people than it does to others? Researchers at the Leibniz Institute for Food Systems Biology at the Technical University of Munich have now come closer to answering this question

Leibniz-Institut für Lebensmittel-Systembiologie an der TU München

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The photo shows two scientists from the Leibniz-Institute for Food Systems Biology at the Technical University of Munich conducting research into coffee flavor in the laboratory. They are wearing lab coats and protective goggles.

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Credit: photo: G. Olias / Leibniz-LSB@TUM

Why does coffee taste more bitter to some people than it does to others? Researchers at the Leibniz Institute for Food Systems Biology at the Technical University of Munich have now come closer to answering this question. They have identified a new group of bitter compounds in roasted Arabica coffee and have investigated how they influence its bitter taste. In addition, they demonstrated for the first time that individual genetic predisposition also plays a role in determining how bitter these roasting substances taste.

Although caffeine has been known as a bitter tasting substance for a long time, even decaffeinated coffee tastes bitter. This shows that other substances also contribute to the bitter taste of roasted coffee. Coline Bichlmaier, a doctoral student at the Leibniz Institute, explains: “Indeed, previous studies have identified various compound classes that are formed during roasting and contribute to bitterness. During my doctoral thesis, I have now identified and thoroughly analyzed another class of previously unknown roasting substances.”

The starting point of her research was the mozambioside contained in Arabica beans. It tastes about ten times more bitter than caffeine and activates two of the approximately 25 bitter taste receptor types found in the human body, namely the TAS2R43 and TAS2R46 receptors. “However, our investigations showed that the concentration of mozambioside decreases significantly during roasting, so that it only makes a small contribution to the bitterness of coffee,” says principal investigator Roman Lang, and continues: ”This prompted us to test whether roasting produces breakdown products of mozambioside are also bitter and could affect coffee’s taste.”

Combination effect and genetic predisposition are important

As the research team shows, seven different degradation products of mozambioside are formed during roasting. These compounds are found in roasted coffee in varying concentrations, depending on roasting temperature and duration, and almost completely pass into the beverage during brewing.

Investigations in a cellular test system established at the institute show that these roasting substances activate the same bitter taste receptor types as mozambioside. Three of the roasting products even had a stronger effect on the receptors than the original compound. However, the researchers found that the concentrations of these roasting products measured in brewed coffee were too low to induce a noticeable taste on their own. Only the combination of mozambioside and its roasting products in a sample led eight out of eleven test subjects to perceive a bitter taste. One person found the taste astringent and two did not perceive any particular taste.

A genetic test showed that taste sensitivity depended on the genetic predisposition of the test subjects: two people had both copies of the TAS2R43 gene variant defective. Seven had one intact and one defective variant of the receptor and only two people had both copies of the gene intact.

What do the results mean for the future?

“The new findings deepen our understanding of how the roasting process influences the flavor of coffee and open up new possibilities for developing coffee varieties with coordinated flavor profiles. They are also an important milestone in flavor research, but also in health research,” says Roman Lang, explaining: ”Bitter substances and their receptors have further physiological functions in the body, most of which are still unknown.” According to Lang, there is still a lot of work to be done, since for many bitter substances in coffee alone, it is not yet known which bitter taste receptors they activate, even though millions of people worldwide drink coffee every day.

Publications:

1) Bichlmaier, C., Fröhlich, S.M., Brychcy, V., Grassl, A., Behrens, M., and Lang, R. (2024). Contribution of mozambioside roasting products to coffee's bitter taste. Food Chem 469, 142547. 10.1016/j.foodchem.2024.142547. https://doi.org/10.1016/j.foodchem.2024.142547

2) Czech, C., Lang, T., Graßl, A., Steuer, A., Di Pizio, A., Behrens, M., and Lang, R. (2024). Identification of mozambioside roasting products and their bitter taste receptor activation. Food Chem 446, 138884. 10.1016/j.foodchem.2024.138884. https://doi.org/10.1016/j.foodchem.2024.138884

More information

Mozambioside
Arabica coffee contains bitter-tasting mozambioside (11-O-β-D-glucosyl-cafestol-2-one). It is a hydrophilic derivative of cafestol that is particularly abundant in naturally caffeine-free varieties. Its perception threshold in humans is 60 ± 10 micromolar (Lang et al., 2015; Lang et al., 2020). Its concentration in raw Arabica coffee is about 0.4–1.2 micromol/g. Roasting breaks down the substance to below the taste threshold in the end product.

Other bitter-tasting roasting substances in coffee
The most important bitter tasting substances that are reportedly formed during roasting include caffeoylquinides, which are formed from chlorogenic acids, diketopiperazines, which originate from coffee proteins, and oligomers of 4-vinylcatechols, which are formed from caffeic acids. These compound classes do impart a bitter taste, but it is not yet known which bitter taste receptor types mediate their perception.

Bitter taste receptors
In humans, about 25 different taste receptor types are responsible for the perception of bitter substances. These bitter taste receptors are not only found in the mouth, but also on cells of other organs and tissues. The many functions they perform there are the subject of numerous studies, including those conducted at the Leibniz Institute for Food Systems Biology at the Technical University of Munich. Various studies already indicate that bitter taste receptors in the respiratory tract help to ward off pathogens and accelerate the movement of cilia. They also suggest that endogenous bitter receptors in the intestines and blood cells support defense mechanisms or are involved in the regulation of metabolism.

Per capita coffee consumption in selected countries worldwide in 2023
https://de.statista.com/statistik/daten/studie/199898/umfrage/konsum-von-kaffee-in-europa/

Global coffee production by variety up to 2023/24
In the production year 2023/24, around 102.2 million 60-kilo bags of Arabica coffee were produced worldwide. For Robusta, the figure was 75.8 million 60-kilo bags.
https://de.statista.com/statistik/daten/studie/224824/umfrage/weltweite-kaffeeproduktion-nach-sorten/

Information About the Institute:

The Leibniz Institute for Food Systems Biology at the Technical University of Munich (Leibniz-LSB@TUM) comprises a new, unique research profile at the interface of Food Chemistry & Biology, Chemosensors & Technology, and Bioinformatics & Machine Learning. As this profile has grown far beyond the previous core discipline of classical food chemistry, the institute spearheads the development of a food systems biology. Its aim is to develop new approaches for the sustainable production of sufficient quantities of food whose biologically active effector molecule profiles are geared to health and nutritional needs, but also to the sensory preferences of consumers. To do so, the institute explores the complex networks of sensorically relevant effector molecules along the entire food production chain with a focus on making their effects systemically understandable and predictable in the long term.

The Leibniz-LSB@TUM is a member of the Leibniz Association, which connects 96 independent research institutions. Their orientation ranges from the natural sciences, engineering and environmental sciences through economics, spatial and social sciences to the humanities. Leibniz Institutes address issues of social, economic and ecological relevance.They conduct basic and applied research, including in the interdisciplinary Leibniz Research Alliances, maintain scientific infrastructure, and provide research-based services. The Leibniz Association identifies focus areas for knowledge transfer, particularly with the Leibniz research museums. It advises and informs policymakers, science, industry and the general public.

Leibniz institutions collaborate intensively with universities – including in the form of Leibniz ScienceCampi – as well as with industry and other partners at home and abroad. They are subject to a transparent, independent evaluation procedure. Because of their importance for the country as a whole, the Leibniz Association Institutes are funded jointly by Germany’s central and regional governments. The Leibniz Institutes employ around 21,300 people, including 12,200 researchers. The financial volume amounts to 2,2 billion euros.

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Journal

Food Chemistry

DOI

10.1016/j.foodchem.2024.142547 

Method of Research

Experimental study

Subject of Research

Not applicable

Article Title

Contribution of mozambioside roasting products to coffee's bitter taste

Article Publication Date

17-Dec-2024

COI Statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper https://www.sciencedirect.com/science/article/pii/S0308814624041979?via%3Dihub

 

Weather change linked to increased risk of Salmonella outbreaks

University of Surrey

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Climate change is impacting the spread of Salmonella, according to new research from the University of Surrey. This research follows previous work from the team, which found that weather change is leading to the spread of dangerous diarrheal illness. 

The study, led by a team of researchers at Surrey’s School of Veterinary Medicine, investigated the impact of different weather factors on the transmission of Salmonella - a leading cause of foodborne illnesses in Europe, accounting for nearly one in three foodborne outbreaks. 

Salmonella is a type of bacteria that can cause food poisoning. It’s found in the intestines of animals and humans and can contaminate food if it’s not cooked or handled properly. Salmonella can cause diarrhoea, fever, and stomach cramps, and it is most prominent in areas with poor sanitation and hygiene. 

In the study, published in the Journal of Infection, researchers compared UK Health Security Agency (UKHSA) data of confirmed cases of Salmonella in England and Wales during 2000-2016 with Met Office data of the time, focusing on 14 different weather factors. This provided a more holistic understanding, which considered the combined effect of multiple weather factors on incidences of Salmonella, leading to an in-depth description of the risk of salmonellosis when we know the local weather during the past days. 

Warmer temperatures (above 10 degrees Celsius), relative humidity, dewpoint temperature (between 7-10 degrees Celsius), and longer days (over 12-15 hours) were identified as key weather factors associated with an increase in Salmonella cases, irrespective of geographical location. These findings were also validated by analysing data from the Netherlands. 

Dr Gianni Lo Iacono, Senior Lecturer in Biostatistics and Epidemiology at the University of Surrey, said: 

“The model we used to analyse the data shows promise, as the findings were replicated across England, Wales and, independently,  in the Netherlands, suggesting a potential for wider application in other European and high-income countries to help gain new insights on the incidence of Salmonella. It would be interesting to investigate this in regions with very different environmental and socio-economic characteristics, like tropical countries.” 

Dr Laura Gonzalez Villeta, the first author of the study and researcher at the University of Surrey, said: 

“The study highlights how weather plays a significant role in Salmonella outbreaks and provides a valuable tool for predicting future risks and tailoring interventions, particularly in the context of climate change.” 

[ENDS] 

• Dr Gianni Lo Iacono is available for interview, please contact mediarelations@surrey.ac.uk to arrange.   

• The full paper is available at the Journal of Infection: https://www.sciencedirect.com/science/article/pii/S0163445325000040 

• An image of Dr Gianni Lo Iacono is attached. 

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Journal

Journal of Infection

DOI

10.1016/j.jinf.2025.106410 

Article Title

Identifying key weather factors influencing human salmonellosis: A conditional incidence analysis in England, Wales, and the Netherlands

 

Green phosphonate chemistry – Does it exist?

University of Eastern Finland

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Phosphorus is a critical raw material that should be recycled more efficiently. There is also a need for more environmentally friendly production methods for organic phosphorus compounds. A recently published review article examines the potential of green chemistry to contribute to these goals in the production and use of multifunctional phosphorus compounds, phosphonates.

Organic phosphorus compounds play a crucial role in several scientific fields, such as chemistry, biology, medicine and pharmacy. These compounds include phosphonates, which have particularly important applications as drugs for the treatment of osteoporosis and other calcium metabolism related diseases, and as corrosion and scale inhibitors, among other things. 

The EU has listed phosphorus as one of the critical raw materials, i.e., raw materials of great economic importance and with a high risk of supply disruption due to the concentration of their sources and the lack of good, affordable substitutes.

“Therefore, one can ask whether it is even relevant to talk about green chemistry for any compound containing non-recycled phosphorus,” notes one of the authors of the review, Staff Scientist Petri Turhanen from the School of Pharmacy at the University of Eastern Finland.

Green chemistry is an area of chemistry and chemical engineering focusing on the design of products and processes that minimise or eliminate the use and generation of hazardous substances. Green chemistry methods are increasingly expected to provide solutions to the world's major environmental problems.

The recently published review article focuses on green methods in the synthesis of phosphonates, as well as the wide range of their applications. In addition, the review discusses the degradation, recovery and recycling of phosphonates.

“Feasible green chemistry methods have already been developed for the synthesis of phosphonates; however, the efficient recovery and recycling of phosphonates or phosphorus still requires a great deal of research,” Turhanen sums up.

The article was an invited paper for Green Chemistry, which is the flagship journal in the field, and it was co-authored with Turhanen by University Researchers Santosh Kumar Adla and Juri Timonen from the School of Pharmacy as well as by a long-term collaborator, Professor Konstantinos D. Demadis from the University of Crete.

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Journal

Green Chemistry

DOI

10.1039/D4GC02940B 

Article Title

Green phosphonate chemistry – Does it exist?

 

New study improves the trustworthiness of wind power forecasts

By applying techniques from explainable artificial intelligence, engineers can improve users’ confidence in forecasts generated by artificial intelligence models. This approach was recently tested on wind power generation by a team that includes experts

Ecole Polytechnique Fédérale de Lausanne

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The researchers and study's co-authors Wenlong Liao and Fernando Porté-Agel. © 2025 EPFL/Alain Herzog - CC-BY-SA 4.0

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Credit: © 2025 EPFL/Alain Herzog

Explainable artificial intelligence (XAI) is a branch of AI that helps users to peek inside the black-box of AI models to understand how their output is generated and whether their forecasts can be trusted. Recently, XAI has gained prominence in computer vision tasks such as image recognition, where understanding model decisions is critical. Building on its success in this field, it is now gradually being extended to various fields where trust and transparency are particularly important, including healthcare, transportation, and finance.

Researchers at EPFL’s Wind Engineering and Renewable Energy Laboratory (WiRE) have tailored XAI to the black-box AI models used in their field. In a study appearing in Applied Energy, they found that XAI can improve the interpretability of wind power forecasting by providing insight into the string of decisions made by a black-box model and can help identify which variables should be used in a model’s input.

“Before grid operators can effectively integrate wind power into their smart grids, they need reliable daily forecasts of wind energy generation with a low margin of error,” says Prof. Fernando Porté-Agel, who’s the head of WiRE. “Inaccurate forecasts mean grid operators have to compensate at the last minute, often using more expensive fossil fuel-based energy.”

More credible and reliable predictions

The models currently used to forecast wind power output are based on fluid dynamics, weather modeling, and statistical methods – yet they still have a non-negligible margin of error. AI has enabled engineers to improve wind power predictions by using extensive data to identify patterns between weather model variables and wind turbine power output. Most AI models, however, function as "black boxes," making it challenging to understand how they arrive at specific predictions. XAI addresses this issue by providing transparency on the modeling processes leading to the forecasts, resulting in more credible and reliable predictions.

Most important variables

To carry out their study, the research team trained a neural network by selecting input variables from a weather model with a significant influence on wind power generation – such as wind direction, wind speed, air pressure, and temperature – alongside data collected from wind farms in Switzerland and worldwide. “We tailored four XAI techniques and developed metrics for determining whether a technique’s interpretation of the data is reliable,” says Wenlong Liao, the study’s lead author and a postdoc at WiRE.

In machine learning, metrics are what engineers use to evaluate the model performance. For example, metrics can show whether the relationship between two variables is causation or correlation. They’re developed for specific applications – diagnosing a medical condition, measuring the number of hours lost to traffic congestion or calculating a company’s stock-market valuation. “In our study, we defined various metrics to evaluate the trustworthiness of XAI techniques. Moreover, trustworthy XAI techniques can pinpoint which variables we should factor into our models to generate reliable forecasts,” says Liao. “We even saw that we could leave certain variables out of our models without making them any less accurate.”

More competitive

According to Jiannong Fang – an EPFL scientist and co-author of the study – these findings could help make wind power more competitive. “Power system operators won’t feel very comfortable relying on wind power if they don’t understand the internal mechanisms that their forecasting models are based on,” he says. “But with XAI-based approach, models can be diagnosed and upgraded, hence generate more reliable forecasts of daily wind power fluctuations.”

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Journal

Applied Energy

DOI

10.1016/j.apenergy.2024.124273 

Method of Research

Computational simulation/modeling

Subject of Research

Not applicable

Article Title

Can we trust explainable artificial intelligence in wind power forecasting?

 

ICARDA and Japan join forces to boost food security in Egypt

International Center for Agricultural Research in the Dry Areas

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Mr. Aly Abousabaa, Director General of ICARDA, met with His Excellency Mr. IWAI Fumio, the Japanese Ambassador to Egypt, on 27 January 2025, in Cairo, to commemorate ICARDA’s recent partnership with the Government of Japan to implement the transformative project Reversing Egypt’s Diminishing Food Security.

The project, made possible through a generous US$750,000 grant from Japan, will target the governorates of Qena, Menya, and Kafr El Sheikh to improve agricultural resilience, optimize resource use, and strengthen rural livelihoods. It will be implemented in collaboration with Egypt’s Ministry of Water Resources and Irrigation (MWRI) and the Ministry of Agriculture and Land Reclamation (MALR).

Building on over 40 years of ICARDA’s experience in dryland regions, the Reversing Egypt’s Diminishing Food Security project aims to empower Egypt’s rural communities to withstand the growing challenges of food insecurity caused by climate change, rapid population growth, and resource scarcity. Key components of the project include introducing green energy-powered irrigation systems, restoring saline-affected lands, and promoting high-quality seeds and modern cultivation techniques. These efforts are projected to directly benefit smallholder farmers and build the capacities of agricultural extension agents and irrigation engineers in Egypt.

This project will integrate cutting-edge technologies, such as meska-shading solar panels, buried-pipe and cement-lining lifted marwas (on-farm water-distribution ditches), internal ditch/drain networks for leaching and transforming highly saline fallow into productive agricultural/aquacultural lands, small-scale solar-powered post-harvest units, and ICARDA’s GeoAgro-Misr digital agricultural advisory smartphone application, to increase water and energy efficiency while supporting sustainable agricultural practices. It will also focus on gender inclusion by empowering women farmers through access to training, small-scale food processing units, and decision-making opportunities.

“This partnership underscores the power of international collaboration to address the urgent issues of food security and climate resilience,” said Mr. Aly Abousabaa. “It is always an honor working with the Government of Japan to bring our innovative solutions to life. I am confident in this project’s ability to create sustainable impacts for Egypt’s agricultural sector.”

During their meeting, Mr. Aly Abousabaa and His Excellency Mr. IWAI Fumio, highlighted the collaborative activities that contributed to reducing rural poverty in the Upper Egypt and Nile Delta Regions of Egypt through improving water rationalization, increasing agricultural productivity for smallholder farmers, and creating economic opportunities for poor rural households. They also discussed how ICARDA’s innovations and several complementary interventions bridged the gap between research and scalability.

“Strengthening food security is one of Japan’s priorities, and even under the influence of factors such as increased food demand and climate change, sufficient and safe food must be available to all people, at all times,” said Ambassador IWAI. “This cooperation with ICARDA will contribute to strengthening water and food security in Egypt, and to sustaining peace and stability in the Middle East and Africa region.”

The Reversing Egypt’s Diminishing Food Security project aligns with Egypt’s “Agricultural Development Strategy Towards 2030” and the United Nations Sustainable Development Goals, particularly SDG 2 (Zero Hunger) and SDG 13 (Climate Action).

This collaboration draws on Japan’s long-standing partnership with CGIAR, which is pivotal in advancing agricultural research and innovation, particularly in addressing water and land scarcity in dryland regions.

ICARDA will continue to foster strategic collaborations while working closely with national partners and governments to deliver climate-smart agri-solutions for improved food and nutrition security and thriving livelihoods of communities in climate-vulnerable dry regions.