Properties of Ultraviolet Irradiated Protein Films

Protein-based films were cast from film-forming solutions of wheat gluten, corn zein, egg albumin, and sodium caseinate. Control and ultraviolet (UV) irradiated (253.7 nm, 51.8 J/m2) films were evaluated for tensile strength, total soluble matter, water vapor permeability, and Hunter L, a, and b color values. UV treatment increased tensile strength of gluten, zein, and albumin films suggesting the occurrence of UV radiation-induced cross-linking within film structures. For caseinate films, UV-curing did not affect tensile strength but substantially reduced total soluble matter. Small but significant decreases in total soluble matter also were noticed for UV-treated zein and albumin films. UV irradiation reduced water vapor permeability of albumin films but did not affect water vapor permeability of the other types of films. Gluten, albumin, and caseinate films had increased yellowness as a result of UV treatment. In contrast, UV treatment decreased the yellowness of zein films, possibly due to destruction of zein pigments by UV radiation.