A method including operating a high impact polystyrene (HIPS) reaction system having a devolatilizer downstream of a polymerization reactor, and from which a HIPS product is obtained, and injecting an antioxidant into the HIPS reaction system prior to the devolatilizer, with the antioxidant being one or more aromatic antioxidants. A HIPS product produced by operating a HIPS reaction system to produce a HIPS product, with the HIPS reaction system including a devolatilizer downstream of a polymerization reactor, and including injecting an antioxidant into the HIPS reaction system prior to the devolatilizer, with the antioxidant being comprising one or more aromatic antioxidants. The antioxidant may comprise at least one thiol group, at least one cresol group, or both. A system for producing the HIPS product is also provided.