Phase transitions of κ‐carrageenan gels in various types of salts

Abstract

Sol-gel and gel-sol phase transitions of k-carrageenan in various types of salts were studied using photon transmission technique. Here, LiCl, NaCl, KCl, MgCl 2 , CaCl 2 , and SrCl 2 were chosen as the proper salts for the k-carrageenan-water system. Photon transmission intensity, I tr was monitored against temperature to determine the sol-gel and gel-sol temperatures (T sg and T gs ) and activation energies (DE sg and DE gs ). It was observed that T gs temperatures were notably higher than T sg due to the hysteresis on the phase transition loops. It was observed that stronger carrageenan gels are formed in the presence of KCl compared to the others.

A thermoreversible double gel: Characterization of a methylcellulose and κ-carrageenan mixed system in water by SAXS, DSC and rheology

“…The results for the 1% and the 2% samples are very similar, only the amplitude of the changes is higher for the higher concentration and the transition temperatures change, as expected. All these results are in good agreement with the described gelation/de-gelation mechanism where first the conformational change of the KC molecules from coil to doublehelices occurs which is then followed by the aggregation of these double-helices to form a large-scale network structure and vice versa [10][11][12][13].…”

“…Further decrease of temperature results in the aggregation between the ordered double-helices and cross-linking leading to the formation of a large-scale network [10][11][12]. Since KC molecules carry charges due to the sulphate groups, the counter ions were found to play an important role in the gelation and corresponding gel characteristics [12][13][14][15][16][17][18][19].…”

Carrageenans as heat stabilisers of white wine

“…The aggregated helical structure can be removed from wine by either settling or centrifugation. The mechanism for heat stabilisation of juice/wine is likely to involve the formation of an electrostatic complex between the negatively charged groups of neighbouring double helices in the kappa ‐carrageenan and positively charged wine proteins that entrap and precipitate the wine haze proteins through sedimentation (Kara et al , Campo et al ). Based on these preliminary trials, three carragenans were selected for larger‐scale trials including natural kappa ‐carrageenan ( k K), ion‐exchanged Na + kappa ‐carrageenan ( k N) and a kappa ‐/ iota ‐carrageenan blend ( ki ) (Table S1).…”

“…In solutions such as wine, ionisable cations and soluble solutes either disturb the formation of the gel or, if formed, is not as stable. The higher viscosity in wine of ion‐exchanged compared with natural carrageenan is likely to be the result of the complex matrix of wine suggesting that the ionic composition and other soluble solutes in wine/juice are likely play a role in affecting its structure (Kara et al ). A comprehensive study of both types of kappa ‐carrageenan salts is needed to fully understand the differences in solubility.…”

Supramolecular structure of methyl cellulose and lambda- and kappa-carrageenan in water: SAXS study using the string-of-beads model

“…Furthermore, there is also a considerable difference between the KC and MC aqueous systems in terms of the thermogelling mechanism. At low temperatures KC is a gel that melts to form a sol at high temperatures (Iijima, Hatakeyama, Takahashi, & Hatakeyama, 2007;Kara, Arda, Kavzak, & Pekcan, 2006;Pekcan & Kara, 2012;Yoshiaki Yuguchi, Thuy, Urakawa, & Kajiwara, 2002;Zhao, Brenner, & Matsukawa, 2013), whereas MC forms a high-temperature gel that transforms to a sol upon cooling to low temperatures (Lin Li, 2002;L Li et al, 2002;Nasatto et al, 2015;Su et al, 2014;Xu, Wang, Tam, & Li, 2004;Zheng, Li, Hu, & Zhao, 2004). It has been proposed that upon cooling the KC molecular coils first transform to double helices, which with further cooling start to crosslink and form the three-dimensional network of an elastic gel (Shtykova et al, 2003).…”