When cooking protein-rich foods in water, it can happen that the contents foam up and are pressed out of the valve as liquid when the steam valve is opened.
This is a ‘normal’ process when steam pressure cooking (even in the usual pressure cooker/pressure cooker). This is particularly common when cooking meat soup (chicken soup, beef soup, etc.). Also with soya beans, for example, as these are very high in protein.
The reason for this is as follows:
Fat and protein in food make liquids ‘foam’ - especially when there is a change in temperature and/or pressure. If the filling quantity is small (less mass), the effect is not so strong that it foams up to the pressure valve. However, if the filling quantity is larger (as with a whole chicken or a large quantity of soya beans in water), the liquid can foam hot out of the valve.
You should therefore leave a pressure cooker (and therefore also the MeinHans) closed for about 20 minutes after pressure cooking protein-rich liquids to allow the pressure inside to drop.
An alternative procedure would be the following:
Take a kitchen towel in your hand and briefly open the steam valve until liquid spurts out. Then close the valve again and place the kitchen towel on the valve. Then release the steam in short bursts: Always wait a moment, then open again briefly. Very soon the pressure will be reduced to such an extent that no more liquid squirts out. Then you can also remove the cloth.