No more bruised mushrooms

Mushrooms are easily affected by bruising. You can see that when mushrooms are packed too tightly in one of those blue containers: they turn brown, which consumers don’t like. That is one reason why Dutch mushroom producers have to pick their mushrooms carefully by hand, one by one. Picking robots are supposed to be the solution but they currently cause too much damage to the mushrooms. That is why there is a need for a robust mushroom that can withstand bruising. PhD student Amrah Weijn discovered that the susceptibility to bruising is partly genetic. She tested 50 different mushroom varieties, including wild varieties. She used a ‘bruise test’ she had developed herself to determine which varieties were best able to withstand bruising. Then she compared the DNA of the susceptible varieties with that of the robust varieties to find the genes that affect susceptibility. She also examined the mushroom’s metabolism to see which compounds cause the brown colour. She found two aromatic compounds that are converted into melanin, the substance that causes the dis­coloration, by an enzyme. The two building blocks for melanin, GHB and GDHB, can now serve as markers – the less of these com­pounds there is, the less the risk of discoloration. This new knowledge has already been used by mush­room companies in crossbreeding experiments. Amrah Weijn obtained her doctorate on 14 June; her supervisor was Harry Wichers, professor of Immune Modulation by Food.