Chitosan molecular weight effect on starch-composite film properties

BOF, J.; BORDAGARAY, V.C.; LOCASO, D.E.; GARCIA, M.A.

FOOD HYDROCOLLOIDS

ELSEVIER SCI LTD

Lugar: Amsterdam; Año: 2015 p. 281 - 294

0268-005X

The aim of this work was to prepare and characterize composite films based on chitosan (CH) and cornstarch (CS), analyzing the influence of the chitosan molecular weight (MW) on film structure andfunctional properties. Three chitosan products were characterized and classified as low (LMW), medium(MMW) and high (HMW) according to its MW. Rheological behavior of filmogenic solutions depend onCH-MW from Newtonian to pseudoplastic one. Chitosan based film physicochemical properties werestrongly affected by its molecular weight: the lower the MW the higher the color differences and filmsolubility. SEM observations demonstrated that plasticized chitosan films exhibited homogeneousstructures, the higher the MW the more compact is the structure and the lower is the water vaporpermeability (WVP, 4.55 ± 0.6 1011 g/m s Pa.). Likewise, CH and CS were compatible polymers whichled to the development of homogeneous blend films. Polymer interactions were evidenced in FTIRspectra by the shifts observed within the region of 1500e1700 cm1, which reduce the hydrophilicgroups? availability of chitosan matrices, leading to a reduction in WVP of composite films. Mechanicalproperties of the developed films were performed through different complementary tests. Chitosan MWaffects both the type and number of interactions, which determine the matrix structure and characteristics.In HMW-CH matrix polymerepolymer interactions are favored, leading to strong and resistantmatrices with high dynamic elastic modulus values. Meanwhile, in LMW-CH one, polymer-plasticizerand polymeresolvent interactions became important and the development of high extensible and solublematerials is privileged.