The influence of a hydroxypropyl-beta-cyclodextrin composite on the gelation of kappa-carrageenan

Although the gelation mechanism of kappa-carrageenan (KC) is well understood, its behavior in the presence of cyclodextrin composites is still rarely studied. To address this lack of research, the influence of a cinnamon essential oil (CEO)/hydroxypropyl-beta-cyclodextrin (HPBCD) composite on the gelation of KC was evaluated using "empty" HPBCD as the control. The gelling and melting temperature, storage modulus (G'), and compression modulus (S) of KC gels increased after the addition of the CEO/HPBCD composite, and these values were greater than those of the control group. G' and S reached maxima at 3% additive amounts. Hydrogen bonds formed after the addition of both additives; however, more hydrogen bonds were formed between KC molecules with HPCDs than with the CEO/HPBCD composites. KC gels containing the composite displayed a more homogeneous and finer structure. Moreover, the crystallinity of KC gels decreased with increasing additive content. The crystalline structure was more complete when the composite was present. HPBCD composites affected KC gelation mainly by (i) facilitating the ordering of KC coils and (ii) restraining the aggregation of KC helices. Hydrogen bonding was suggested to be one of the factors influencing the interaction.