Native hybrid carrageenans from Sarcopeltis skottsbergii and Sarcothalia crispata: The role of counterions on their gelling properties

Carrageenans are red seaweed polysaccharides of great importance as gelling agents in the food texture market. The hybrid kappa/iota-carrageenan is extracted from certain cold-water species and its unique properties have given rise to growing demand for this biopolymer. Gelation of these polysaccharides is affected by the valency and, sometimes, the identity of counterions. The main objectives of this work were to investigate the role of potassium and calcium ions on the gelation of the native hybrid carrageenans from Sarcopeltis skottsbergii and Sarcothalia crispata from the South American Atlantic coast, and to optimize the structural properties of these gels. Response surface methodology was used to analyze the effects of carrageenan concentration, salt concentration, and KCl center dot CaCl2 ratio, on the rheology, texture, syneresis after 50 % deformation, and color of these gels. Both native carrageenans presented high extraction yield (42.73 +/- 0.20 g/100 g for S. skottsbergii and 20.43 +/- 7.64 g/100 g for S. crispata) and formed either weak or strong gels upon the addition of salt. Carrageenan and salt concentrations increased gel strength, but also increased turbidity. Moreover, KCl fraction also increased gel strength, attributed to the predominance of the kappa diad in these carrageenans, whose gelation is favored by potassium ions. All samples showed syneresis after deformation, being minimized with higher carrageenan and salt contents. Optimal compositions predicted by the selected models to maximize gel strength and minimize syneresis and haze, were 1.13 % carrageenan, 0.39 M salt and a proportion of 0.85 KCl for S. skottsbergii, and 1.16 % carrageenan, 0.36 M salt and a proportion of 0.85 KCl for S. crispata. Predicted responses for these optimal compositions were in accordance with the observed responses. Considering the worldwide growing demand for kappa/iota-carrageenan in the food industry, S. skottsbergii and S. crispata from the South Atlantic represent a potential source of these biopolymers.

Automated summary

This study investigates the effects of carrageenan concentration, salt concentration, and KCl center dot CaCl2 ratio on the gelation properties of carrageenans from Sarcopeltis skottsbergii and Sarcothalia crispata. The results show that higher concentrations of carrageenan and salt increase gel strength but also increase turbidity. Increasing the KCl fraction also increases gel strength. The optimal compositions predicted by the models are in line with the observed responses. Considering the increasing demand for carrageenan in the food industry, S. skottsbergii and S. crispata could be potential sources of these biopolymers.