In our previous study, semi-transparent and flexible biodegradable films were successfully prepared from myofibrillar proteins of blue marlin meat. The objective of this study was to elucidate the mechanism of film formation. Effect of pH on the amount of surface hydrophobicity and surface SH group in the film-forming solution, solubility of film proteins in various protein denaturant solutions, SDS-PAGE, and addition effect of protein denaturants in the film-forming solutions were investigated. At first, the necessity of unfolding of protein molecules was revealed for the formation of self-standing films. Secondly, the important chemical bondings involved in the protein-protein interactions were confirmed to be hydrophobic interaction for acidic condition, hydrogen bondings for neutral condition, and hydrophobic interaction and disulfide bondings for alkaline condition.
Although heat sterilization is commonly used to sterilize polysaccharides to be used as a food additives, it is difficult to sterilize heat-resistant bacteria even by heat sterilization method and heat sterilization causes changes of physical properties and color tone in appearance of polysaccharides. It is thus required to develop novel non-heat sterilization method that causes no changes in physical properties of polysaccharides. We investigated effects of electron beam irradiation on physical properties of polysaccharides. Electron beam irradiation mostly caused decrease of average molecular weight, leading to the decrese in viscosity and gel strength. Magnitude of changes in these physical properties depended on polysaccharides. It was also found that physical properties of gum arabic were hardly changed by electron beam irradiation. We discussed some factors causing difference in physical properties of polysaccharides by electron beam irradiation in terms of the properties of polysaccharides.