C. Le Tien et al., Development of biodegradable films from whey proteins by cross-linking andentrapment in cellulose, J AGR FOOD, 48(11), 2000, pp. 5566-5575
When cross-linked by heating or by gamma -irradiation and entrapped in cell
ulose, whey proteins can generate insoluble biofilms with good mechanical p
roperties and high resistance to attack by proteolytic enzymes. Interchain
cross-linking of proteins generated an increase in the puncture strength, a
nd a decrease in water vapor permeability. Gelatin was added in film formul
ation as a stabilizer to improve the puncture strength and film appearance.
The structure of the biofilms was also analyzed. SDS-PAGE revealed that he
ating and gamma -irradiation produce an increase of the molecular weight of
the cross-linked protein. Size exclusion chromatography showed a molecular
mass of 40 kDa for un-cross-linked whey proteins, whereas for the soluble
fractions of the crosslinked proteins, molecular distributions were between
600 and 3800 kDa for the heated proteins and between 1000 and 2000 kDa for
gamma -irradiated proteins. No major alteration of the structural conforma
tion of the proteins was observed by FTIR for biofilms obtained after heat
treatment, whereas gamma -irradiation induced some modifications in the pro
tein structure. X-ray diffraction analysis suggests that cross-linking by g
amma -irradiation seems to modify the conformation of proteins, which becam
e more ordered and more stable.