Estudo da formação de hidrogéis da Blenda de Chia/Pectina por radiação ionizante

Abstract

Biopolymers have been shown a promising alternative in obtaining of new materials, as well as in study of polymeric blends for several applications, such as in hydrogels production, in biomedical area and pharmaceutical industry. In this work, the behavior of chia hydrocolloid (HC) and apple pectin blends was evaluated against gamma radiation. The hydrocolloid was extracted and analyzed for its proximate composition: ash (12.68%), moisture (3.9%), proteins (7.49%), lipids (7.43%), crude fiber (5.78%) and nitrogen free extract (62.75%). Matrices and blend solutions were formulated in two blocks: the first containing HC, pectin, glycerol (5%) in pHs 4 and 8, the second, containing HCP (purified hydrocolloid), pectin, glycerol (20%) and radiation doses (0.0; 2.5; 5.0; 7.5 or 10.0 kGy), with 0.0 and 2.5 kGy films being the best in terms of flexibility and fracture resistance. The 0.0 and 2.5 kGy films being the best in terms of flexibility and fracture resistance. The formulations were characterized in terms of their viscosity, presence of charges (PZC), identification of functional groups (FTIR and FTIR-ATR), surface and cross-section morphology (SEM), thermal behavior (TGA and DSC) and crosslinking capacity (by freezing cycles test and gel content). The viscosity test revealed that the chia matrices (HC and HCP) presented a thixotropic behavior, with their viscosity decreased with the increase of shear rate, and increased when the rotational movement stops, which can be explained by the presence of charges causing a more intense entanglement between the chains. This fact could be confirmed by the analysis of point of zero charge, which presented a value of 7.47, which is different from the pHs worked. The cross-section micrographs of formulations irradiated at 2.5 kGy dose showed homogeneous regions in comparison to non-irradiated ones. Doses higher than 2.5 kGy led to decompression of these regions, indicating degradation of polymer chains. In the infrared analysis of the matrices and blends, the presence of hydroxyl groups, free carboxylates and carboxyls of uronic acids was observed, in addition to stretches of C–O–C groups of esters and ethers. The formulations irradiated at 2.5 kGy dose showed a reduction in the ratio between –OH and C–O–C band intensity when compared to non-irradiated ones, which is an indication of crosslinking, which could be confirmed for the 30/70 (HCP/Pec/Gli 20%) blend by gel fraction, since the non-irradiated formulation showed a 10.0% residue, and in the irradiated ones, the largest amount was 22.12% at 2.5 kGy dose. For the 50/50 blend (HCP/Pec/Gli20%) the ideal dose is below 2.5 kGy (22.90%) and not irradiated (26.22%). Thus, the 2.5 kGy dose is the best among studies for hydrogel formation. The results obtained in this work were satisfactory, allowing to select the doses and formulations to improve the applicability to solid hydrogels production.