The best way to find out is to go to the airline's web site, or a generic travel booking site such as Expedia, enter JNB as your point of departure and MAD as your destination, and see if it comes up with the connection that you are thinking of taking. If it does it's within the MCT (Minimum Connecting Time), if it doesn't then it isn't.

Airport web sites are also tend to list MCTs, have you checked there?