A developmental process, independent of morphogenetic (shape) change, that is required for a type B pancreatic cell to attain its fully functional state. A type B pancreatic cell is a cell located towards center of the islets of Langerhans that secretes insulin. [ GOC:BHF http://purl.obolibrary.org/obo/CL_0000169 ]
Synonyms: pancreatic beta cell maturation pancreatic B cell maturation