Hydrothermal extraction and thorough characterization of carrageenans and proteins from Gigartina pistillata

Carrageenan, an interesting biopolymer from red seaweed, possesses a myriad of applications in food, nutraceutical, or pharmaceutical industries. Although its conventional extraction used to be performed with alkaline solvents, water extraction under subcritical conditions is an alternative eco-friendly technique that has gained popularity in recent years. This work evaluates the recovery and characterization of carrageenan and proteins from Gigartina pistillata. The highest number of proteins was identified at the lowest processing tempeartures. Extracted carrageenan exhibits molecular weights greater than 500 kDa and good rheological behaviour, with interest for food applications and for the formulation of hydrogels when mixed with KCl. The carrageenans and carrageenan hydrogels presented interesting properties such as good thermal stability until 170 °C (TGA-DTG) and show characteristic bands of kappa/iota carrageenans in FTIR studies. Greater cell viability than 70% were achieved on NIH/3T3 fibroblast at carrageenan concentrations of 0.05 and 0.025%, whereas carrageenan extracted at 160 °C (concentration of 0.025%) displays a lower inflammatory action than other samples. In this sense, in this work the eco-friendlier extracted carrageenan was thoroughly characterized and its potentiality to be used in the biomedical field was evaluated. [Display omitted] •Gigartina pistillata red seaweed is an interesting source for the valorization of carrageenan.•Carrageenans woth molecular weights >500 kDa could be suitable for food applications.•Carrageenan (C160) at 0.025% enabled cell viability >70% and the lowest inflammatory effect.•Carrageenan hydrogels presented adequate rheological properties for food applications.