EFFECT OF PH ON PROPERTIES OF WHEAT GLUTEN AND SOY PROTEIN ISOLATE FILMS

Soy protein isolate (SPI) and wheat gluten (WG) films can be cast from appropriate solvent systems. Such films can find use as edible or non edible food packaging materials. The effect of pH of WG and SPI film-f orming solutions on film formation, tensile strength (TS), percentage elongation at break (E), and water vapor permeability (WVP) was invest igated. WG films formed within pH 2-4 and 9-13, whereas SPI films form ed within pH 1-3 and 6-12. Film formation was inhibited by poor protei n dispersion around the isoelectric pH region of SPI (pH 4.5) and WG ( pH 7.6). SPI films prepared from pH 6 to 11 had significantly (P < 0.0 5) higher TS, higher E, and lower WVP than films from pH 1 to 3. WG fi lms produced under alkaline conditions had significantly (P < 0.05) hi gher TS than films processed under acidic conditions.