100B-36 |
Effect of aging on soy protein films properties |
A. N. MAURI, F. J. Speroni, and M. C. Añón. Centro de Investigación y Desarrollo en Criotecnología de Alimentos, Universidad Nacional de La Plata - CONICET, 47 y 116, La Plata, 1900, Argentina Edible films and coatings made from biopolymers, like proteins, hold promise for innovative uses in food protection and preservation. Aging of this materials could include chemical and physical changes that occur in the material after exposure to environmental conditions over a period of time. The evaluation of these changes is important to determine the film application. The aim of this work was to study the effects of aging at two common storage conditions on the physical properties of soybean isolate films. Soy protein isolate (SPI) was produced by dilute alkali extraction from defatted soy flour, followed by the isoelectric precipitation of proteins. Films were prepared by casting, from alkaline dispersions (pH: 10.5) that contained 5% of soy protein isolate and 2.5 % of glycerol, which was used as plasticizer. Protein dispersions were dried at 60 °C and films were aged at two storage conditions: a) 4°C and 85 % RH and b) at 20°C and 80% RH. Water vapor permeability (WVP), color, mechanical properties (obtained by puncture and tensile tests) and glass transition temperature of films were measured at regular intervals of time for up 45 days. WVP and color coordinates (L, a and b) were unaffected during film aging, and no differences in value were seen between both storage conditions. Films aged at 4°C showed a smooth variation in mechanical properties. During films storage, the strain at break increased and the stress at maximum force and Young`s modulus decreased. Mechanical properties of films aged at 20°C were not much affected. Furthermore structural properties of films (microstructure, solubility in buffers with different chemical action, and electrophoresis) are currently under study in order to correlate the changes in physical properties with the film structure. The stability of films during storage made them promising for several applications in food packaging.
Session 100B, Food Packaging
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