Rapeseed does not just contain oil but high-quality protein, too. However,
protein extracts from rapeseed have an intense, bitter off-taste, which
prevents it from being a protein source for human nutrition. In a first-ever
step towards developing rapeseed for the human protein supply, food chemist
Thomas Hofmann and his team at the Technical University of Munich (TUM)
identified the substance that is pivotal for the bitter taste in rapeseed.

The researchers investigated three different protein isolates using mass
spectrometric analysis methods and taste tests. All three isolates had a
protein content of 80 to 90 percent. The researchers show for the first time
that 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 kilogram. The rapeseed meal and napin
isolate had less than a tenth of the quantity, but still tasted bitter in
the sensory test.

"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.

[www.tum.de]