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Hydrogels consisting of a blend of sodium alginate and k -carrageenan aqueous solutions were prepared using Ca 2+ 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 k -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 k -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 k -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.

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This study aimed to evaluate carotenoid degradation kinetics in a beverage coloured with pumpkin juice concentrate during storage at dark and illuminated conditions at four temperatures (10, 20, 35 and 45 °C). Carotenoids were quantified by HPLC-DAD, and kinetic parameters for carotenoid degradation were estimated by one-step nonlinear regression analysis. During dark storage, degradation kinetics was modelled by fractional conversion (all-trans-β-carotene) and zero-order equations (all-trans-antheraxanthin, all-trans-lutein, all-trans-violaxanthin and all-trans-neoxanthin). Storage of samples in a climatic chamber with intense light intensity (1875–3000 lux) accelerated the carotenoid losses. At illuminated conditions, degradation followed a first-order (all-trans-lutein, all-trans-violaxanthin and all-trans-neoxanthin) and fractional conversion model (all-trans-β-carotene and all-trans-antheraxanthin). Carotenoid degradation followed an Arrhenius temperature-dependency, with values lower than 50 kJ/mol. Degradation was shown to be mainly by oxidative reactions. Packaging under minimal oxygen conditions, use of antioxidants (e.g., ascorbic acid), and proper choice of light sources at retail shelves may be considered to optimize the pigment retention in a carotenoid-coloured beverage during storage.

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