What is the shiny stuff on grapefruits?

The shiny stuff on grapefruits is a natural wax that is produced by the fruit's skin. This wax helps to protect the fruit from damage caused by moisture, sunlight, and insects. It also gives the fruit its characteristic glossy appearance.

The wax on grapefruits is not harmful to consume, but some people prefer to remove it before eating the fruit. This can be done by simply washing the fruit under warm water and then rubbing it with a clean cloth.