Rheological and calorimetric study of the sol–gel transition of κ-carrageenan

Seawater at the nanoscale: marine gel imaged by atomic force microscopy

“…4)-3,6-anhydro-D-galactose in which b-galactose is partially sulphated at C4 position, is an anionic sulphated polysaccharide extracted from red algae (Rhodophyceae). Superior DH gel to DH m detected in marine gel was also observed in k-carrageenan (Iijima et al, 2007;Nunez-Santiago and Tecante, 2007) and was ascribed to a larger energy release during double helix aggregation than that required to melt the aggregate (Nunez-Santiago and Tecante, 2007). The difference between T m and T gel obtained for both, marine gel and k-carrageenan, is known as the thermal hysteresis, which appears as a consequence of aggregation of helical structures into three-dimensional networks.…”

“…The enthalpy changes expressed per gram of organic matter in the gel phase are: DH m ¼ 0.5 J/g for the heating-scan transition corresponding to melting, and DH gel ¼3.7 J/g for the cooling transition corresponding to gelling. As there are no published data for the gel-sol transition of marine gels, we shall refer to the model system, k-carrageenan, commonly used in DSC (Mangione et al, 2003;Iijima et al, 2007;Nunez-Santiago and Tecante, 2007) and AFM (McIntire and Brant, 1997b;Ikeda et al, 2001;Funami et al, 2007) studies of thermoreversible polysaccharide gelation. k-Carrageenan, composed ideally of a disaccharide repeating unit b (1!3)-D-galactose-4-sulphate and a (1!…”

The molecular organogel n-decane/12-hydroxyoctadecanoic acid: Sol–gel transition, rheology, and microstructure

“…The temperature of the peak maximum in a recorded heat flow vs. temperature curve was taken as the sol-gel transition temperature (according to ref. [18][19][20]), while the area under the peak yielded the sol-gel transition enthalpy. The errors of the measured data were ΔT sol-gel = ± 1.4 K and Δ(Δ sol-…”

“…the sol-gel transition is reversible. Note that hysteresis effects have been described for sol-gel transitions [19,20], i.e. the transition from the gel to the sol usually occurs at higher temperatures than that from the sol to the gel.…”

“…3). As the sol-gel transition temperature T sol-gel we took the peak maximum [18][19][20]. The reproducibility M a n u s c r i p t 9 of the latter was ± 1.4 K because gel melting peaks are rather broad, reflecting that the sol-gel transition is not a simple first-order process but takes place within a certain temperature range [18].…”