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The interest toward alginate and nanoemulsion-based hydrogels is driven by the wide potential of application. These systems have been noticed in several areas, ranging from pharmaceutical, medical, coating, and food industries. In this investigation, hydrogels prepared through in situ calcium ion release, starting from lemongrass essential oil nanodispersions stabilized in alginate aqueous suspensions in the presence of the nonionic surfactant Tween 80, were evaluated. The hydrogels prepared at different concentrations of oil, alginate, and calcium were characterized through rheological tests. Flow curves demonstrate that the hydrogels share shear thinning behavior. Oscillatory tests showed that the strength of the hydrogel network increases with the crosslinker increase, and decreases at low polymer concentrations. The hydrogels were thixotropic materials with a slow time of structural restoration after breakage. Finally, by analyzing the creep recovery data, the hydrogel responses were all fitted to the Burger model. Overall, it was demonstrated that the presence of essential oil in the proposed hydrogels does not affect the mechanical characteristics of the materials, which are mainly influenced by the concentration of polymer and calcium as a crosslinker.

The growing demand for ready-to-eat fresh fruits has led to set-up appropriate strategies for preserving fruit quality and freshness of such commodities. To slow down the deterioration events such as respiration, moisture loss and enzymatic activity, ready-to-eat products should be protected with an edible film. A suitable coating should combine hydrophilic and hydrophobic features to ensure good mechanical and gas barrier properties. Alginate/essential oil nanoformulations, one with low and the other with high oil content, here proposed to protect apple pieces during storage, were first characterized through dynamic light scattering and rheology. The effect of the application of the nanoformulations on the quality parameters of apples stored at 4 °C was considered by evaluating weight loss, pH and titratable acidity, total phenols content and the fruit appearance during storage. Mainly on the basis of pH and titratable acididty variation, the nanoformulation with low oil content resulted eligible for preserving the quality of fresh-cut apple pieces during storage.

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The necessity of producing innovative packaging systems has directed the attention of food industries towards the use of biodegradable polymers for developing new films able to protect foods and to extend their shelf-life, with lower environmental impact. In particular, edible films combining hydrophilic and hydrophobic ingredients could retard moisture loss, gas migration and ensure food integrity, reducing the necessity of using synthetic plastics. Alginate-based films obtained from emulsions of lemongrass essential oil (at 0.1% and 0.5%) in aqueous alginate solutions (1%), with Tween 80 as surfactant (0.3%), were obtained by casting and characterized as to microstructure and thermal behavior, as well as tensile, barrier and optical properties. Films were also crosslinked through spraying calcium chloride onto the film surface and the influence of oil emulsification and the crosslinking effect on the final film properties were evaluated. The film microstructure, analyzed through Field Emission Scanning Electron Microscopy (FESEM) revealed discontinuities in films containing essential oil associated with droplet flocculation and coalescence during drying, while calcium diffusion into the matrix was enhanced. The presence of essential oil reduced the film stiffness whereas calcium addition lowered the film’s water solubility, increasing tensile strength and reducing the extensibility coherent with its crosslinking effect.