Desenvolvimento de blendas de amido de inhame modificado com quitosana e pva

Abstract

The aim of this study were to modify chemically the yam starch (Dioscorea esculenta L.) by oxidation and phosphorylation reactions, produce blends with chitosan (CH) and poly (vinyl alcohol) (PVA) and evaluate their physico-chemical and functional properties. The oxidized starch (AOX) had a high degree of substitution (DS=1.86) which promoted major changes in the granular structure showing characteristics of an amorphous material, whereas the phosphorylation was very subtle (GS=0.002), remaining its granular structure and crystalline pattern B-type of native yam starch. The phosphorylated starch (AF) showed improvement in paste stability and low tendency to retrogradation, unlike the AOX which showed no viscosity profile due to depolymerization caused by the reaction. The AF/CH/PVA blends showed good characteristics of water vapor permeability, low solubility in phosphate buffer and distilled water as compared to native starch. The blends AF showed significant swelling in buffer due to crosslinking between the phosphate groups of the solution and the film, which is desirable for a possible application of such films as dressings. The changes in intensities and shapes of the FTIR bands as well as variations in temperatures of gelatinization confirmed the interaction of PVA and chitosan with the starch chains in the films. The addition of PVA improved the characteristics of the films offering high flexibility. The AF blends showed no activity in the inhibition of S. aureus and P. aeruginosa, but the AOX blends, although not showing effectiveness in inhibition of P. aeruginosa, showed activity against strains of S. aureus, especially AOX50 and AOX70 blends, which may favor their use as inhibitors against proliferation of these microorganisms in infections.