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Cast Films from Soy Protein Isolates and Fractions¹

¹Journal Series No. 11507, Agricultural Research Division, Institute of Agriculture and Natural Resources, University of Nebraska-Lincoln. ²Graduate research assistant and associate professor, respectively, Department of Food Science and Technology, University of Nebraska, Lincoln, NE 68583-0919. ³Postdoctoral research associate, professor, and associate professor, respectively, Department of Biological Systems Engineering, University of Nebraska, Lincoln, NE 68583-0726. ⁴Corresponding author. Fax: (402)472-1693.

Glycerol-plasticized soy protein films were cast from alkaline aqueous film-forming solutions of laboratory-prepared 7S, 11S, and soy isolate (LSI) fractions and from commercial soy isolate (CSI). Tensile strength (TS), elongation at break (E), water vapor permeability (WVP), total soluble matter (TSM), protein solubility (PS), and Hunter L, a, and b color values of these films were determined. The 11S films had greater TS than 7S films (P < 0.05), while LSI films had greater TS than CSI films (P < 0.05). No significant differences were detected among mean E values and among mean WVP values of all films (P > 0.05). The 7S films had higher TSM and PS values than 11S films (P < 0.05). CSI films were significantly darker (lower L value) and more yellow (greater positive b value) than LSI films (P < 0.05).