Physically cross-linked hydrogel based on sorghum starch: development and characterization

The objectve of this work was to develop a hydrogel based on white sorghum starch and characterize its visual aspects, behavior in the presence of water, morphology, and texture profile. Six hydrogel samples were developed from sorghum starch, chitosan, and different proportions of citric acid through thermal gelatinization. The hydrogels were then physically crosslinked by freeze-thawing. All six samples showed high water absorption capacity and low syneresis rate, ranging from 0.35% (sample 5, with the highest concentration of citric acid) to 9.75% (sample 6, without the addition of citric acid). After lyophilization, all six samples exhibited stable and intact structures after immersion in water; however, those with citric acid maintained greater structural integrity after 24 h. The water activity values among the samples ranged from 0.995 ± 0.002 to 0.999 ± 0.001, characterizing a high aw, as they were close to 1. Regarding water release from the hydrogels, the six samples presented values ranging from 0.08 ± 0.03 to 25.35 ± 1.90%. Water loss values ranged from 0.03 to 0.44 g among the six hydrogel samples. Regarding the pH of the hydrogel samples, the results ranged from 3.36 ± 0.01 to 7.66 ± 0.01. Morphological analysis of the hydrogels revealed that the crosslinking process promoted the formation of a three-dimensional polymeric matrix, resulting in highly porous hydrogels with greater water absorption capacity. The texture profile of the developed hydrogels revealed the formation of firm and cohesive gels, with good integrity and high resistance. Fourier transform infrared spectroscopy (FTIR) identified the characteristic functional groups of starch and citric acid. This study presents, for the first time, the development of hydrogels based on sorghum starch, a raw material still unexplored for this application, highlighting the potential of sorghum as a sustainable and environmentally friendly alternative. Furthermore, the developed material stands out as a promising matrix for the incorporation of bioactive compounds, expanding its possible technological applications.