Modification of the properties of milk protein films by gamma radiation and polysaccharide addition

Abstract

This study has demonstrated that gamma radiation induced an improvement of barrier properties and tensile strength of films containing calcium caseinate, whey protein isolate and glycerol (1:1:1) through creation of a crosslinked β-structure. Up to 32 kGy the effect was accompanied by an increase in rigidity and was larger with increasing radiation dose. The irradiation of protein solutions also caused improvement of puncture strength of films prepared with potato starch, soluble potato starch or sodium alginate addition (at a level of 50 g kg-1 of total proteins). Addition of potato starch did not influence mechanical properties of films but significantly improved barrier properties. Addition of sodium alginate resulted in improvement of both puncture strength and barrier properties. Addition of sodium alginate to irradiated protein solution resulted in films revealing the greatest improvement in properties. Gels prepared using irradiated protein solutions mixed with calcium salt were stronger than gels prepared using non-irradiated solutions owing to the preferred binding of calcium ions to the crosslinked protein network. Presence of sodium alginate and potato starch weakened the interaction of proteins with calcium ions owing to entrapment of proteins in the polysaccharide network, while addition of soluble potato starch promoted these interactions. © 2006 Society of Chemical Industry.