LAUSR

The objective of this study was to investigate the influence of gelation on the ice recrystallization inhibition (IRI) activity of κ-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 κ-carrageenan sucrose solution and compared the results with the IRI activity. Viscoelastic properties of the residual liquid at −12 °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 κ-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 κ-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.