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31.01.2019 – 14:46

Technische Universität München

Bitter rapeseed: How rapeseed could be used as a protein source for human nutrition

TECHNICAL UNIVERSITY OF MUNICH

Corporate Communications Center

Phone: +49 89 289 10510 - e-mail: presse@tum.de - web: www.tum.de

This text on the web: https://www.tum.de/nc/en/about-tum/news/press-releases/detail/article/35222/

High resulution image: https://mediatum.ub.tum.de/1472323

NEWS RELEASE

Bitter rapeseed

How rapeseed could be used as a protein source for human nutrition

Rapeseed doesn't just contain oil but high-quality protein, too. However, protein extracts from rapeseed have an intense, bitter off-taste. A team led by food chemist Thomas Hofmann has now identified the substance that is pivotal for the bitter taste. This is a first step towards developing rapeseed for the human protein supply.

According to the Food and Agriculture Organization of the United Nations (FAO), the demand for food will approximately double by 2050 due to the growing world population. "Bottlenecks are to be expected in this context, particularly in protein supply," says Thomas Hofmann, who heads the Chair of Food Chemistry and Molecular Sensory Science at the Technical University of Munich (TUM).

According to Hofmann, who is also Director of the Leibniz-Institute for Food Systems Biology, it is therefore important to develop new plant protein sources for human nutrition. And rapeseed is a good local source.

Rapeseed contains high-quality protein

Rapeseed doesn't just contain oil but high-quality protein too, which contains many essential amino acids. Worldwide around 1.12 million tons of crude protein are produced annually from rapeseed oil. Although farmers have long used this so-called rapeseed cake as a protein feed for animals, it has not played a role as a protein source in human nutrition so far.

One reason is that the accompanying substances contained in rapeseed strongly impair the taste of the obtained protein isolates. These substances include, for example, very bitter-tasting secondary plant constituents. Hofmann and his team therefore looked into the issue of which bitter substances cause the rapeseed protein's unpleasant bad taste.

The key substance that makes rapeseed protein taste bitter

The researchers investigated three different protein isolates using mass spectrometric analysis methods and taste tests. The first isolate was an extract of all the proteins contained in rapeseed meal. The second isolate predominantly contained cruciferin and the third napin, which are the rapeseed's two main storage proteins. All three isolates had a protein content of 80 to 90 percent.

As the investigations show for the first time, a compound called kaempferol 3-O-(2'''-O-sinapoyl-ß-sophoroside) is the key substance that makes protein extracts from rapeseed inedible. The cruciferin isolate in particular contained a large amount of this bitter substance with 390 milligrams per kilogramme. The rapeseed meal and napin isolate had less than a tenth of the quantity, but still tasted bitter in the sensory test.

Starting point for new processes

"Since we now know the cause of the bitter off-taste, it is much easier to develop suitable technological processes or breeding strategies that can be used to produce tasty, protein-rich foods from rapeseed," said co-author Corinna Dawid, who heads the Phytometabolomics research group at TUM.

Publication:

C. Hald, C. Dawid, R. Tressel, T. Hofmann:

Kaempferol 3-O-(2'''-O-sinapoyl-?-sophoroside) causes the undesired bitter taste of canola/rapeseed protein isolates

J Agric Food Chem, 67: 372-378, DOI: 10.1021/acs.jafc.8b06260

https://pubs.acs.org/doi/10.1021/acs.jafc.8b06260

Further information:

The research project was funded by the Federal Ministry of Education and Research (BMBF) as part of the RaPEQ project (031B0198D). The project partner was the Pilot Pflanzenöltechnologie e.V. research institute in Magdeburg.

High resolution images:

https://mediatum.ub.tum.de/1472323

Contact:

Prof. Dr. Thomas Hofmann

Technical University of Munich

Chair of Food Chemistry and Molecular Sensory Science,

Director of the Leibniz-Institute for Food Systems Biology at TUM

Tel.: +49 8161 71 2902 - E-mail: thomas.hofmann@tum.de

Dr. Corinna Dawid

Technical University of Munich

Chair of Food Chemistry and Molecular Sensory Science,

http://www.molekulare-sensorik.de/index.php?id=75&L=1

Tel.: +49 8161 71 2923 - E-mail: corinna.dawid@tum.de

The Technical University of Munich (TUM) is one of Europe's leading research
universities, with around 550 professors, 42,000 students, and 10,000 academic
and non-academic staff. Its focus areas are the engineering sciences, natural
sciences, life sciences and medicine, combined with economic and social
sciences. TUM acts as an entrepreneurial university that promotes talents and
creates value for society. In that it profits from having strong partners in
science and industry. It is represented worldwide with the TUM Asia campus in
Singapore as well as offices in Beijing, Brussels, Cairo, Mumbai, San Francisco,
and São Paulo. Nobel Prize winners and inventors such as Rudolf Diesel, Carl von
Linde, and Rudolf Mößbauer have done research at TUM. In 2006 and 2012 it won
recognition as a German "Excellence University." In international rankings, TUM
regularly places among the best universities in Germany. www.tum.de
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