Rheological Characterization of Hydrogels from Alginate-Based Nanodispersion

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

Veiled Extra Virgin Olive Oils: Role of Emulsion, Water and Antioxidants

This review traces the current knowledge on the effects of various factors and phenomena that occur at interface, and the role of dispersed phase on the physicochemical, sensorial and nutritional characteristics of veiled extra virgin olive oil (VVOO). Since 1994 there have been numerous articles in the literature regarding the peculiar characteristic of unfiltered olive oil, so-called veiled or cloud virgin olive oil. It is a colloidal system (emulsion–sol), where the continuous lipidic phase dispreads mini droplets of milling water, fragments of cells and biotic fraction obtained from oil processing. During storage, the dispersed phase collapses and determines the quality of the virgin olive oil (VOO). The observed phenomena lead to worsening the quality of the product by causing defects such as oxidation of phenols, triacylglycerols hydrolysis and off-flavor formation. The addition of bioactive compounds, such as vitamins, on product based on VVOO, must take into account the eventual synergistic effect of individual substances. The role of the interphase is crucial to the synergic activity of bioactive molecules in improving oxidative stability, sensorial and health characteristics of VVOO

Rheological Properties of Alginate–Essential Oil Nanodispersions

Due to its favorable structural properties and biocompatibility, alginate is recognized as a suitable versatile biopolymer for use in a broad range of applications ranging from drug delivery, wound healing, tissue engineering, and food formulations such as nanodispersions. Rheological analysis plays a crucial role in the design of suitable nanoemulsion based coatings. Different essential oil and alginate nanodispersion compositions stabilized by Tween 80 were analyzed for rheological and conductometric properties. The results confirmed that the nanoformulations shared a pseudoplastic non-Newtonian behavior that was more evident with higher alginate concentrations (2%). Nanodispersions made of alginate and essential oil exhibited a slight thixotropic behavior, demonstrating the aptitude to instantaneously recover from the applied stress or strain. Oscillatory frequency sweep tests showed a similar fluid-like behavior for 1% and 2% alginate nanodispersions. Finally, it was demonstrated that advantages coming with the use of the essential oil are added to the positive aspects of alginate with no dramatic modification on the flow behavior

Quality Control of Fresh-Cut Apples after Coating Application

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