Ice recrystallization inhibition of commercial κ-, ι-, and λ-carrageenans

The synergistic effect of hydroxypropyl methylcellulose and κ-carrageenan or pectin on anti-freezing

Ten polysaccharides were mixed to select polysaccharides with the synergistic anti-freezing effect in this study. It was found that hydroxypropyl methylcellulose (HPMC) and pectin (PEC) or κ-carrageenan (κ-CAR) synergistically decreased the freezing temperature of water and enhanced the ice recrystallization inhibition activity. Moreover, HPMC/κ-CAR exhibited greater synergy than HPMC/PEC. Raman spectroscopy analysis demonstrated that these polysaccharides increased the disorder of water molecules and inhibited the transition from liquid water to solid ice, and HPMC and PEC or κ-CAR had a synergistic effect on increasing the disorder of water molecules. Particularly, dynamic ice-shaping measurements showed that the HPMC/κ-CAR mixture changed circular ice into hexagonal ice in 20.0 % sucrose solution, whereas the HPMC/PEC mixture did not. Moreover, κ-CAR was more compatible with HPMC than PEC. The above differences might explain why κ-CAR was more effective than PEC in improving the anti-freezing ability of HPMC.

Investigation of κ-Carrageenan's Ice-Binding Properties Using Molecular Dynamics Simulation

Recrystallization of ice crystals during storage of frozen food, cells, or medical samples causes serious damage to the stored material. To mitigate this damage, additives such as κ-carrageenan, a polysaccharide derived from algae, can be employed. Experimental results demonstrated that κ-carrageenan strongly inhibits ice recrystallization and alters the ice crystal morphology, suggesting ice-binding properties. However, a binding of κ-carrageenan to ice crystals has not yet been shown, and the underlying mechanism of its recrystallization inhibition activity remains unclear. In this study, molecular dynamics simulations using different κ-carrageenan molecules and ice planes were performed to shed light on this. The results revealed that κ-carrageenan is able to interact with the basal plane and primary and secondary prism planes, but the binding appears to be reversible, at least for the investigated molecular sizes. In addition, the formation of a double helix did not affect the binding affinity. Hydrogen bond formation and the integration of κ-carrageenan's oxygen atoms into the ice lattice structure facilitate the interaction with the ice crystal. These findings provide further insights into the recrystallization inhibition of polysaccharides and foster the tailored design of effective freeze-protection molecules.

Lambda carrageenan displays antiviral activity against the infectious pancreatic necrosis virus (IPNV) by inhibiting viral replication and enhancing innate immunity in salmonid cells

Sulfated polysaccharide lambda carrageenan (λ-CGN) was evaluated for its antiviral effect against IPNV using the in vitro infection model of CHSE-214 salmonid cells. A plaque reduction lysis assay revealed that λ-CGN has an IC50 of 0.9 μg⋅mL-1, CC50 > 128 μg⋅mL-1 and a Selectivity Index (SI) > 142. In comparison, iota, kappa carrageenans and lambda oligo-carrageenan (λ-OC) were less effective than λ-CGN against IPNV. λ-CGN showed no virucidal activity when applied directly to viral particles. Time of addition experiments showed that pre-treatment, co-treatment, and post-treatment with λ-CGN significantly reduced viral RNA copies in the cell supernatant. Additionally, a decrease in intracellular viral RNA was observed with pre-treatment and post-treatment, indicating an impact on different stages of viral replication. Polyacrylamide gel electrophoresis of IPNV genomic RNA in presence of λ-CGN showed a reduction in the level of viral genomic RNA. Confocal microscopy confirmed the intracellular localization of λ-CGN, suggesting that λ-CGN may inhibit the synthesis of IPNV genomic RNA. Moreover, cells pre-treated with λ-CGN showed an increased expression of innate immunity genes CXCL11, IL1β, IFNa, and IRF3. These findings highlight the need for further research to confirm the in vivo pharmacological potential of λ-CGN as a new antiviral agent in salmonids.

Furcellaran: Impact of Concentration, Rheological Properties, and Structure on Ice Recrystallization Inhibition Activity

Recrystallization is considered the main damaging mechanism during the frozen storage of biologic materials. In this study, furcellaran, a polysaccharide related to κ-carrageenan, was studied for its concentration-dependent effect on ice crystal growth and recrystallization. The structure and sulfate content of the utilized furcellaran was analyzed by 1H nuclear magnetic resonance spectroscopy, ion chromatography, and high-performance size-exclusion chromatography. Additionally, the rheological properties of furcellaran solutions were investigated. Our findings demonstrate that furcellaran inhibits ice growth as effectively as κ-carrageenan. Furthermore, the rheological properties change with increasing furcellaran concentration, resulting in a gel-like consistency at 5 g/L, which coincides with decreased recrystallization inhibition activity and larger crystals. This suggests that gel formation or a gel-like consistency has to be avoided for optimal recrystallization inhibition activity.

Composition-antifreeze property relationships of gelatin and the corresponding mechanisms

The inherent functional fractions (gelation and ice-affinitive fractions) of gelatin enable it as a promising cryoprotectant alternative. However, the composition-antifreeze property relationships of gelatin remain to be investigated. In this study, the HW-PSG and LW-PSG fractions of gelatin from fish scales were obtained, according to the critical gelation conditions and ice-binding measurements, respectively. Thermal hysteresis (THA) value, associated with ice nucleation, of LW-PSG was higher than that of HW-PSG. Besides, the relatively low-sized ice crystals (210-550 μm2) indicated that HW-PSG showed strong ice recrystallization inhibition (IRI) ability, compared to other groups. These results suggested that LW-PSG inhibited ice nucleation, while HW-PSG displayed the strong IRI ability. Furthermore, the antifreeze mechanisms were clarified through IRI measurements and molecular dynamics simulation. The minimum size of ice crystals was found for HW-PSG gels with dense microstructure, suggesting the HW-PSG retarded the growth of ice crystals by restricting the migration and phase transformation of water molecules. The hydrogen bond interactions between the ice crystal surface and ASN1294 and PRO1433 residues of LW-PSG, and hydrophobic interactions contributed to inhibiting the nucleation of ice crystals. This study provided some references to further enhance antifreeze performance of gelatin by modulating fragment composition.

Self-assembly of tamarind seed polysaccharide via enzymatic depolymerization and degalactosylation enhanced ice recrystallization inhibition activity

Polysaccharides are becoming potential candidates for developing food-grade cryoprotectants due to their extensive accessibility and health-promoting effects. However, unremarkable ice recrystallization inhibition (IRI) activity and high viscosity limit their practical applications in some systems. Our previous study found a galactoxyloglucan polysaccharide from tamarind seed (TSP) showing moderate IRI activity. Herein, the enhancement of the IRI performance of TSP via enzymatic depolymerization and degalactosylation-induced self-assembly was reported. TSP was depolymerized and subsequently removed ∼40 % Gal, which induced the formation of supramolecular rod-like fiber self-assembles and exhibited a severalfold enhancement of IRI. Ice shaping assay did not show obvious faceting of ice crystals, indicating that both depolymerized and self-assembled TSP showed very weak binding to ice. Molecular dynamics simulation confirmed the absence of molecular complementarity with ice. Further, it highlighted that degalactosylation did not cause significant changes in local hydration properties of TSP from the view of a single oligomer. The inconsistency between molecular simulation and macroscopic IRI effect proposed that the formation of unique supramolecular self-assemblies may be a key requirement for enhancing IRI activity. The findings of this study provided a new opportunity to enhance the applied potential of natural polysaccharides in food cryoprotection.