Rheology of κ/ι-hybrid carrageenan from Mastocarpus stellatus: Critical parameters for the gel formation

• Hybrid carrageenan (KI) sol–gel diagram depends on M. stellatus seaweed powder size.
• Larger KI content and ionic strength (NaCl) favour the formation of stronger gels.
• Short maturation times (<20 min) and absence of synaeresis is observed in KI gels.
• Progel and gel setting temperatures depended on KI and NaCl content, but gel melting is invariant.
• Tested KI gels show a range of properties for a wide number of applications.

The sol–gel diagrams of kappa/iota-hybrid carrageenan (KI) extracted from Mastocarpus stellatus powders with two different average particle sizes of the seaweed powders (117.0 μm and 77.5 μm) prior to the biopolymer extraction, are reported for the first time, together with rheological properties of obtained KI gels. Extraction yields for KI isolated from algae and average molecular weight of KI, determined by gel permeation chromatography, decreased with increasing the particle size of the powder. Rheological results indicated that tested samples exhibited stable and weak gel properties, except those prepared at 1.5% KI in 1.0 mol/L NaCl where stronger gels were found. Aqueous KI extracts with larger molecular weight led to stronger gels and also formed gels at lower biopolymer concentration in NaCl above 0.15 mol/L. All gels reached stability after 20 min of maturation. The data sets showed a strong temperature dependency. Gel setting temperatures significantly depended on the KI and NaCl content, whereas gel melting temperatures (68.0 ± 0.7 °C) were independent of both salt concentrations.