ULTRAVIOLET-RADIATION AFFECTS PHYSICAL AND MOLECULAR-PROPERTIES OF SOY PROTEIN FILMS

Films were cast from heated, alkaline aqueous solutions of soy protein (5 g/100 mt water) and glycerin (50% w/w of protein). Control and ult raviolet (UV) irradiated (13.0, 25.9, 38.9, 51.8, 77.8, or 103.7 J/m(2 )) films were evaluated for tensile strength (TS), elongation at break (E), water vapor permeability (WVP), and Hunter L, a, and b color val ues. TS increased (P<0.05) linearly while E decreased linearly with UV dosage. WVP was not affected (P>0.05) by UV irradiation. UV treatment intensified the yellowish coloration of films (increased +b values). SDS-PAGE patterns for UV-treated samples revealed bands of aggregates, increasing in intensity with UV dosage, which were absent in control samples. These changes suggested UV-induced cross-linking in films.