Erika Mascheroni

Encapsulation of volatiles in nanofibrous polysaccharide membranes for humidity-triggered release

A single-step electrospinning process will be applied to a blend of edible carbohydrate polymers (pullulan and β-cyclodextrin) to encapsulate bioactive aroma compounds and allow a humidity-triggered release. The encapsulation is rapid and efficient and the final product is an active nanofibrous membrane that can be directly used for food or active packaging applications. The membrane hosts small and homogeneously dispersed crystals of cyclodextrin-aroma complexes which are formed during the electrospinning. With this type of structure, the release of aroma compound is negligible at ambient conditions (23 °C and 55% UR) even at high temperature (up to 230 °C), and it occurs beyond a given relative humidity threshold (90%), useful for food packaging applications. The mass fraction of free aroma released is directly related to the water activity of the system, namely, φ=aW(n)/(aW(n)+Kapp) explaining the observed key role played by the relative humidity on the release of the aroma compounds.

Comparison of cellulose nanocrystals obtained by sulfuric acid hydrolysis and ammonium persulfate, to be used as coating on flexible food-packaging materials

Cellulose nanocrystals (CNCs), extracted from trees, plants, or similar cellulose-containing materials, can be used in combination with other materials to improve their performance or introduce new applications. The main purpose of this study was to compare and understand the potentialities, as coatings for Poly(ethylene terephthalate) films, of CNCs obtained starting from the same cotton linters by two different processes: sulfuric acid hydrolysis and a less common treatment with ammonium persulfate (APS), able to provide also a cellulose oxidation. The results showed that CNCs produced through the APS treatment showed higher charge densities, due to the carboxylic groups formed during the process, higher crystallinity, higher clarity of the solution and, as a consequence, higher transparency of the coating. These characteristics provide a higher oxygen barrier with respect to the CNCs produced by the H2SO4 treatment, together with the availability of active sites for potential surface modification or chemical grafting. Both CNC coatings showed oxygen permeability coefficients that were lower than synthetic resins commonly used in flexible packaging. Furthermore, they did not significantly affect the optical properties of the substrate, while revealing good friction coefficients. Due though to the moisture sensitivity of the coating and its non-sealable nature, similar to EVOH or PVOH oxygen barrier synthetic resins, CNCs developed using APS will need to be laminated with another plastic layer such as a polyolefin. They could then be used to enhance the final properties of packaging solutions as an alternative to conventional food-packaging materials for perishable food products, while reducing their environmental impact with a thin layer of a bio-based polymer.

Shelf life of case-ready beef steaks (Semitendinosus muscle) stored in oxygen-depleted master bag system with oxygen scavengers and CO2/N2 modified atmosphere packaging

This study aims to evaluate the stability of beef from Semitendinosus muscle packaged in oxygen permeable wrapped-tray units and stored in a master bag system, with and without oxygen scavengers. Changes in the atmosphere composition, microbiological indexes, myoglobin forms and color parameters were monitored during the storage in master bag, blooming and display life. The presence of scavengers reduced rapidly the oxygen concentration and maintained it at values not detectable instrumentally. Within few days of storage in master bags, the resolution of the transient discoloration was completed and the meat quality was maintained over the anoxic storage. After the removal from master bags meat bloomed completely reaching OxyMb level and Chroma values higher than those on fresh meat at t(0). During 48 h of display life at 4 °C, quality attributes had a decay slower than samples stored traditionally in air. Without scavengers the oxygen caused the irreversible discoloration within 7 days, due to the formation of metmyoglobin on the surface.