Different concentrations of ferulic acid were added to film-forming solutions when preparing soy protein isolate-based edible films. The results showed that an optimal concentration of ferulic acid increased the tensile strength, elongation percentage at break and antioxidant activity of films for preservation of fresh lard. The optimal concentration for ferulic acid in film forming solution is 100 mg/100 g. Moreover, the properties of the film were further improved when ferulic acid was oxidized by hydrogen peroxide. A possible mechanism for the role of ferulic acid in the preparation of SPI-based films is that it reacted with amino acids and increased cross-linking of the protein. It is interesting that the absorbance wavelength for ferulic acid-protein (or amino acids) is much longer than ferulic acid or protein (or amino acids) alone. The absorbance shift indicates the formation of a ferulic acid-protein cross-link that may enhance the shelf life of foods by decreasing oxygen permeability. (c) 2004 Elsevier Ltd. All rights reserved.