Jangal's mind was occupied with Kenichi's saying that he's Boazanian too. To test Kenichi's claim, Jangal made a robot that could spray Voltes team with Boazanian germ that can cause sickness to non-Boazanian beings. Boazanians would build natural immunity against the germ. So if Kenichi's claim is true, he and his brothers would not be affected by the Boazanian germ for too long, as their bodies would start producing antibody against it.