A Wageningen PhD student has discovered one of the substances responsible for making coffee brown. ‘There are lots more similar compounds,’ says Koen Bekedam of the Food Chemistry Group. ‘This happened to be the first we could isolate.’
Green unroasted coffee beans contain a protein with side chains of the sugar arabinogalactane, says Bekedam. ‘This is arabino-galactane-protein. When the coffee is roasted a cascade of reactions takes place, in which sugars react with proteins, leading to the creation of the AGP melanoidin complex.’ Melanoidins are brown coloured molecules that are also in chocolate and fried meat. Because they are important for the colour and taste of products, food technologists focus a lot of their research on the reactions in which melanoidins are produced. Bekedam hopes to be able to influence the taste of coffee as well as the colour. ‘If you keep coffee hot for too long the compounds react further and the coffee becomes bitter. Maybe our research will lead to a milder coffee.’ Bekedam’s research is published in the Journal of Agricultural and Food Chemistry of 7 February.