Interactions between modified starch and carrageenan during pasting

This study focused on starch/carrageenan blends. Its aim was to develop a method to evaluate if carrageenan was trapped or excluded by starch granules during pasting, and quantify the amount of interacting polysaccharide in the case of trapping. Four carrageenan samples and a modified waxy maize starch were used, where starch was pasted in carrageenan solutions. The set up method permitted, using an indirect titration, to evaluate the concentration of carrageenan in the supernatants of those ‘pasted blends’. The quantity of carrageenan trapped by starch granules could then be obtained. The percentage of trapped kappa-carrageenan was higher than for iota-carrageenan. Increasing the rigidity of kappa-carrageenan chains decreases the amount of trapped carrageenan. To the contrary, decreasing the molecular weight leads to an increase in carrageenan trapping. Evolution of the carrageenan concentration in the supernatant versus the starch concentration after gelatinization. Carrageenans: C1 (▪); C2 (▪); C3 (▪);C3d (▪). The dotted lines correspond to the two extreme hypotheses: H1 (—) carrageenan chains enter with the solvent inside the starch granule during gelatinization; H2 (– –) no carrageenan chain enters the starch granules during gelatinization. [Display omitted] •Starch granules more or less trap carrageenan depending on the carrageenan sample.•Small Mw and high flexibility of chains favour carrageenan–starch interaction.•Carrageenan charge does not seem to be an important parameter.•Use of sheared carrageenan gels to determine carrageenan concentration.•Confocal microscopy for observing carrageenan interacting with starch granules.