A STUDY ON THE MECHANICAL PROPERTIES OF PEA PROTEIN ISOLATE FILMS

Effects of glycerol (Gly) (3-7% w/w) and sorbitol (Sor) (4-8% w/w) concentration, pH (7.0, 9.0, 11.0) and heating (90C, 20 min) of film-forming solutions (FFS) on the tensile strength (sigma(max)), elongation at break (epsilon(b)), elastic modulus (EM) and puncture strength (PS) of pea protein isolate (PPI) films were investigated in this study. The films plasticized with Sor exhibited significantly higher sigma(max), EM, PS and lower eb, in comparison with Gly-plasticized films. Incorporation of higher Gly and Sor amounts in the films led to decreases in sigma(max), EM and PS but did not affect epsilon(b). An increase of pH value from 7.0 to 11.0 resulted in improved sigma(max) of Gly-plasticized films, while for films with Sor, this effect was not observed. In turn, epsilon(b) and PS of the films were significantly increased by alkalization of FFS, regardless of the plasticizer type. Generally, an improvement in mechanical strength of PPI films produced from heated FFS was observed. X-ray diffraction analyses of Gly-and Sor-plasticized PPI films did not show any differences in their internal structure.