ISBN 9783843932035

978-3-8439-3203-5, Reihe Verfahrenstechnik

Andreas Leiter
Investigation of the ice recrystallization inhibition mechanism of kappa-carrageenan in frozen model solutions

133 Seiten, Dissertation Karlsruher Institut für Technologie (2017), Softcover, A5

Zusammenfassung / Abstract

The quality of frozen food products depends to a large extent on recrystallization processes during distribution and storage, which result in an increase in mean ice crystal size. Especially for ice cream, the increase in ice crystal size deteriorates the ice cream texture and thus limits the shelf life. Therefore, inhibition of ice recrystallization is of great concern to ice cream manufacturers.

The hydrocolloid κ-carrageenan has a high potential as recrystallization inhibitor as it exhibits strong ice recrystallization inhibition (IRI) activity in a simplified model system like sucrose solution. κ-carrageenan is a linear, sulfated polysaccharide extracted from certain species of red seaweeds. The underlying IRI mechanism of κ-carrageenan is not yet understood. Two possible IRI mechanisms of κ-carrageenan are mainly presumed. On the one hand, some researchers hypothesize that the formation of a κ-carrageenan gel is responsible for its IRI activity. On the other hand, there are researchers assuming that IRI activity originates from a direct binding of the hydrocolloid to the ice crystal surface similar to the proposed mechanism of ice-binding proteins (IBPs). However, the weight average molecular weight of κ-carrageenan is significantly larger than the molecular weight of IBPs. Therefore, there is the hypothesis that only κ-carrageenan molecules with a low molecular weight of the κ-carrageenan sample having a wide molecular weight distribution exhibit IRI activity.

Although κ-carrageenan exhibits strong IRI activity in a simplified model system like sucrose solution, almost no IRI activity occurs if it is used in a more complex system like ice cream. However, in order to use κ-carrageenan as an ice recrystallization inhibitor in complex systems, factors like process parameters or interactions with other substances affecting its IRI activity must be known. Therefore, the first objective of this thesis was to investigate the influence of selected factors like heating temperature, pH or the presence of ions as well as the molecular weight on the IRI activity of κ-carrageenan under defined conditions. The second objective was to gain a deeper understanding of the underlying IRI mechanism of κ-carrageenan. Therefore, the hypotheses that the formation of a κ-carrageenan gel is responsible for its IRI activity and that only κ-carrageenan molecules with a low molecular weight exhibit IRI activity was investigated.