Radiochemical transformation of mucilage extracted from Opuntia ficus-índica using gamma radiation

Gamma irradiation is a powerful tool for modifying the physicochemical properties of polymers. Gamma radiation has been widely used to carry out reactions such as crosslinking, depolymerization, and graft copolymerization, with a wide variety of synthetic and natural polymers. Although gamma irradiation proved to be useful to modify the chemical properties of several polysaccharides, this method has not been applied to mucilage. However, irradiation could bring beneficial changes to mucilage for its use in different applications. Thus, the aim of this work was to study the radiochemical transformation of mucilage extracted from Opuntia ficus-indica using gamma radiation. Results obtained from FTIR-ATR, pH and electrical conductivity in aqueous solution showed that decarboxylation of mucilage occurs applying a radiation dose from 2 to 12 kGy. Further, it was observed that thermal stability of mucilage was enhanced with a radiation dose of 2 and 6 kGy. The decarboxylation degree was proportional to the radiation dose in the interval of 0-12 kGy. Further, mucilage was irradiated in the presence of acrylic acid forming mucilage/PAA hydrogels with high swelling capacity. The best swelling capacity (734%) was observed for the hydrogel obtained applying 2 kGy of gamma radiation. Hydrogels prepared with higher radiation doses (4-20 kGy) showed lower swelling capacity and higher thermal stability, which suggest a higher crosslinking degree. The experiments performed in this work were performed using 100 mg of mucilage but gamma irradiation allows a high scalability of the process. The usefulness of gamma irradiation relays on the development of a method for preparing hydrogels by an easy and scalable method.