Mechanical properties of tapioca-starch edible films containing sorbates.

FAMÁ L., ROJAS A.M., GOYANES S. Y GERSCHENSON L.N.

LEBENSMITTEL-WISSENSCHAFT UND-TECHNOLOGIE-FOOD SCIENCE AND TECHNOLOGY

Academic Press-ELSEVIER Sci. Ltd. Institut fur Lebensmittel-und Emahrungswissenschaften.

Lugar: ETH-Zentrum, CH-8092 Zurich, Suiza.; Año: 2005 vol. 38 p. 631 - 639

0023-6438

The effect of sorbates present on mechanical properties of edible films prepared with suspensions of tapioca starch containing glycerol, was studied. Films were prepared by casting the systems after gelatinization. The storage modulus (E') and the tangent of the phase angle (tan delta) of the films piece were determined by a Dynamical Mechanical Thermal Analyzer along 8 weeks of storage at relative humidity (RH) of 57.5% and at 25ºC. Stress-strain behavior along quasi-static tests was also analysed using the same device. Results obtained showed that sorbate incorporation resulted in a decrease (around 75%) of E' and an increase (about 200%) of tan delta  after 2 weeks of storage. Antimicrobial presence also affected film performance along storage: it showed a continuous decrease of tan delta along 8 weeks of storage as well as an increase in the tendency to rupture with time. Films without sorbate showed an increase of tan delta along 4 weeks and they presented rupture for all storage periods studied. Aging of strach, characteristics of the network as well as sorbate destruction along storage, are responsible for the changes observed in mechanical properties of the films along 8 weeks.