The objective of this study was to investigate the influence of molecular weight of kappa-carrageenan on its ice recrystallization inhibition (IRI) activity. To reduce the molecular weight, acid hydrolysis with 0.1 M trifluoroacetic acid (TFA) at 80 degrees C or 0.1 M hydrochloric acid (HCl) at 60 degrees C was performed. In addition, molecular weight was reduced by dialyzing kappa-carrageenan against demineralized water. It was demonstrated that IRI activity of kappa-carrageenan decreases with decreasing molecular weight, which is contrary to previous studies. It was shown in our study that the different results may be attributed to an aggregation of kappa-carrageenan molecules due to high NaCl concentration, originated from HCl and subsequent neutralization with NaOH. This aggregation causes a decrease in IRI activity. Furthermore, it was shown that the addition of a small amount of NaCl can lead to an increase in IRI activity of kappa-carrageenan. (C) 2017 Elsevier Ltd. All rights reserved.