Can the drying treatment modify the rheology of Chondrus crispus hybrid carrageenans hydrogels?

This work deals with the influence of dehydration treatment of the red macroalga Chondrus crispus prior to extraction of carrageenans on the hydrogels rheological features. The emerging microwave hydrodiffusion and gravity technique, freeze-drying and the conventional convective air drying were selected as dehydration treatment to pretreat the alga before the recovering of the carrageenans based on the results optimized in a parallel work. Fundamental structural and thermorheological measurements were performed to analyze the features of the sustainably extracted hybrid carrageenans using only water as extractive agent. The molecular weight distribution and the degree of hybridization of the kappa/iota hybrid carrageenans varied markedly depending on the dehydration treatment. Rheology testing showed that systems made with the extracted carrageenans exhibited weak and intermediate gel features, short maturation time (less than 30 min) and absence of syneresis during the studied cold storage. A strengthening of the viscoelastic properties of the hydrogels was identified for those made with carrageenans extracted after microwave treatment, where the most hermos-stable gels were prepared with the hybrid carrageenans with higher molecular weights. Gel setting temperatures were highly dependent on the drying pretreatment of the alga, whereas gel melting ones were practically invariant. Overall, the proposed microwave treatment delivered hybrid carrageenans with enhanced rheological features by means of a more sustainable and efficient treatment.