Characterization of Soybean Protein Concentrate?stearic Acid/Palmitic Acid Blend Edible Films

K. DE LA CABA; C. PEÑA; E. CIANNAMEA; P.M. STEFANI; I. MONDRAGON; R.A. RUSECKAITE

JOURNAL OF APPLIED POLYMER SCIENCE

JOHN WILEY & SONS INC

Año: 2012 vol. 124 p. 1786 - 1807

0021-8995

The effect of incorporating commercial stearicacid/palmitic acid blend (SA/PA, 63/37 wt %) into hydrophilicsoybean protein concentrate (SPC) film-forming solutionsat neutral and alkaline pH on some selected propertiesof edible cast films was investigated. SA/PA-added SPC filmexhibited a significant increase in translucency, being morerelevant for films obtained at pH 7. This was associated withthe more heterogeneous morphology of such films asobserved by scanning electron microscopy. Calorimetricmeasurements and X-ray diffraction studies confirmed thepresence of crystalline fatty acids in films at pH 7 and newcrystalline structures at pH 10 due to interactions or reactionsbetween SPC and SA/PA blend. Fourier Transform infraredspectroscopy results confirmed the incorporation of fattyacids into SPC and revealed the occurrence of interactionsbetween both components, depending on the film-formingemulsion pH. Moisture absorption isotherms at high relativehumidity (RH) were determined and experimental data wereadequately fitted by Peleg?s empirical equation. Control SPCfilms produced at pH 7 were distinctly more moisture resistantthan those at pH 10 owing to the more charged proteinmolecules at alkaline pH. The increased moisture resistanceof SA/PA-added-SPC film at pH 10 was related to the morehomogeneous dispersion of fatty acid particles within theprotein matrix. VC 2011Wiley Periodicals, Inc. J Appl Polym Sci 000:000?000, 2011