Methylcellulose (MC) and kappa carrageenan (KCG) are widely used in food and pharmaceutical industries as a viscosity modifier, a gelling aid, and a film former due to their reversible thermal gelation properties. Thermoreversible gelation of MC/salt, MC/KCG/water, and MC/KCG/salt mixtures was investigated utilizing dynamic and steady shear rheological measurements. It was found that for the MC/salt mixture, gelation temperatures decreased linearly with increasing salt concentrations independent of valences of cations and molar concentrations of anions. For the MC/KCG blend, double gelation was not observed, and KCG is not influenced or disturbed the gelation properties of MC. Double gelation was observed for the mixture of MC/KCG/KCl for the low concentration of salts of 0.01 M KCl and 0.04 M KCl with the maximum moduli values for the mixture of MC/KCG/0.04 M KCl and then gradually decreased with increasing KCl salt concentration and eventually became similar to the gelation of MC solution. Therefore, KCl concentration played a major role in double gelation properties of MC/KCG/KCl mixture. It was also found that for the MC/KCG/KCl system, gelation transition matrices are linearly depending on salt concentration and independent of KCG and salt type. It was shown that for MC/salt mixture, solution rheology follows the principle of time–temperature superposition (TTS) below the gelation temperature. However, TTS failed above the gelation temperature. TTS also failed for MC/KCG and MC/KCG with low KCl concentration mixtures.
|State||Published - 2018|