Resin masterbatch compositions are provided as closed end pellets having a core including at least one additive and an outer layer comprising a polymer encapsulating the core, in which the thickness of the outer layer if from 0.001 mm to 1 cm. A stabilized composition is prepared from an organic material to be stabilized and the resin masterbatch composition. A process for producing the resin masterbatch composition includes co-extruding in tubular form a core material encapsulated by an outer layer, wherein the core material comprises at least one additive, and the outer layer comprises a polymer, to form a filled tube; passing the filled tube into a sealing device that cuts the filled tube into multiple discrete segments seals and simultaneously seals each end of each discrete segment, thereby forming closed end pellets; and cooling the closed end pellets.