Ice recrystallization inhibition activity of chemically defined carrageenans

Carrageenans are sulfated galactans from algae which are commonly used as thickeners, gelling agents, or stabilizers. It has been demonstrated that they also have significant ice recrystallization inhibition (IRI) activity. Previous studies mainly focused on κ-carrageenan, but recent studies suggested that other carrageenans such as ι-carrageenans or carrageenans with multiple structural elements also have this functionality. Therefore, the aim of our study was to analyze the IRI activity of carrageenans with defined chemical structures and associated cations. For this purpose, pure κ and ι-carrageenans as well as several hybrid carrageenans showing broad heterogeneity with regards to the molecular structure and the cations present were investigated. The selected commercial samples were subsequently converted into their potassium, calcium and (in part) sodium forms. Chemical characterization of the modified carrageenans demonstrated that the molecular structure was unaltered by the applied procedures and that the carrageenans were successfully converted into the different cation forms. The analysis of the IRI activity demonstrated that both molecular structure and associated cations had an influence on carrageenan functionality. Pure κ-carrageenan and hybrid carrageenans with consecutive κ-units showed a high IRI activity, whereas ι-carrageenan was less active. For κ-carrageenan, the potassium form showed a clearly higher activity than the calcium form, whereas the calcium form was more active for hybrid carrageenans and ι-carrageenans. Our results significantly expand the knowledge on the relationship between the molecular composition and the IRI activity of carrageenans. Furthermore, they can be used to optimize carrageenan production to obtain an enhanced IRI activity.