Characterization of porcine plasma protein-based films as affected by pretreatment and cross-linking agents

The effects of pretreatment and cross-linking agents on properties of porcine plasma protein-based film were investigated. Based on sodium dodecyl sulfate polyacrylamide gel electrophoresis and solubility study, porcine plasma protein-based film was stabilized mainly by hydrogen bond, while film with pretreatment (pH 10 and heated for 30 min) contained hydrogen bond and hydrophobic interaction. The incorporation of glyoxal or caffeic acid resulted in the increase in protein cross-links stabilized by both disulfide and non-disulfide covalent bonds. Nevertheless, the prior oxygenation had no marked impact on the property of film added with caffeic acid. α-Chymotrypsin was more effective than pepsin in hydrolysis of films. Greater thermal stability with an increase in the melting point was observed in film incorporated with caffeic acid, indicating a greater degree of cross-linking. The coincidental increase in initial temperature of film degradation was noticeable. The FTIR spectra revealed the intermolecular interaction between protein molecules as indicated by the shift of amide-I peak.