Influence of gelation on ice recrystallization inhibition activity of κ-carrageenan in sucrose solution

The objective of this study was to investigate the influence of gelation on the ice recrystallization inhibition (IRI) activity of kappa-carrageenan. It is well known, that the addition of salt can promote gelation. Therefore, we used different cations (Na+, Li+, Ca2+, K+) and anions (Cl-, Br-, I-, NO3-, SO42-) in different concentrations to change the viscoelastic properties of a kappa-carrageenan sucrose solution and compared the results with the IRI activity. Viscoelastic properties of the residual liquid at -12 degrees C and the degree of aggregation were characterized by oscillatory rheological measurements and compared with ice crystal sizes observed over a storage time of 96 h. Results show that the addition of 0.03 M Ca2+, K+, or Na+ cations or 0.03 M Cl- or SO42- anions leads to a significant reduction of IRI activity compared to a pure kappa-carrageenan sucrose solution. In addition, increasing the salt concentration decreases significantly the IRI activity with the exception of NaI showing no decreased IRI activity. Rheological experiments indicate that aggregation of kappa-carrageenan molecules and thus the formation of a gel-like character is responsible for the decreased IRI activity. The addition of NaI prevents aggregation which is already known from the literature and therefore IRI activity retains. (C) 2016 Elsevier Ltd. All rights reserved.