Encapsulation of ginger oil in alginate-based shell materials

Abstract

Hydrogels consisting of a blend of sodium alginate and κ-carrageenan aqueous solutions were prepared using Ca2+ as the gelling agent in a shell material formulation for encapsulation of food-grade ginger oil. A preliminary study on the rheological and textural behavior of two hydrogels prepared from (1) alginate water solution and (2) alginate blended with κ-carrageenan in water showed that the latter produced gels with higher values of elastic and viscous moduli and gel strength, related to added mechanical rigidity. In the encapsulation of ginger oil, 4 formulations of shell material were prepared from 1% w/w alginate solution and from the blend of 1% w/w alginate solution with 1.5% w/w κ-carrageenan (at 80:20 v/v ratio) with and without incubation in a 0.1 w/w chitosan solution as a final coating in a two-stage capsule hardening procedure. The ability of the formulated shell materials to protect the encapsulated ginger oil from oxidative degradation was measured using both primary and secondary oxidation products using peroxide value, p-anisidine value, and thiobarbituric acid reactive substances. Encapsulated ginger oil gave lower values of the oxidation products compared to unencapsulated. Moreover, the ginger oil extracted from capsules with alginate and κ-carrageenan, along with chitosan as the final coating, showed the lowest content of oxidation products throughout the storage period, suggesting a better protection of ginger oil.