This study aimed at determining the effect of chitosan coating on shelf life extension of salmon ( Salmo salar ) fillets. The success of edible coatings depends highly on their effective wetting capacity of the surfaces on which they are applied. In this context in a first stage the surface properties of salmon fillets and the wetting capacity of the coatings on fish were evaluated. In terms of wettability there were no significant differences (p > 0.05) between the solutions presenting higher values (solutions 1-4); therefore, solution 1 with a spreading coefficient (Ws) of -4.73 mN m(-1), was chosen to be subsequently analyzed and applied on fish fillets. For shelf life analyses the fillets were coated and stored at 0 °C for 18 days. The control and coated fish samples were analyzed periodically for total aerobic plate count (TPC), pH, total volatile base nitrogen (TVB-N), trimethylamine (TMA), thiobarbituric acid (TBA), and ATP breakdown products (K value). The results showed that fish samples coated with chitosan presented a significant reduction (p < 0.05) for pH and K value after 6 days and for TVB, TMA, and TBA values after 9 days of storage, when compared to control samples. In terms of microbial growth, a slower increase in TPC was observed for the coated fish, indicating that chitosan-based coatings were effective in extending for an additional 3 days the shelf life of the salmon. These results demonstrate that chitosan-based coatings may be an alternative for extending the shelf life of salmon fillets during storage at 0 °C.

Polysaccharide multinanolayers are becoming a new and general means of modifying and functionalizing surfaces of several materials. This is achieved through changing the interfacial properties of those surfaces followed by sequential adsorption of e.g., polysaccharides. Knowledge of properties of polysaccharide solutions such as zeta potential (Zp) and mean hydrodynamic diameter (Z-average) is crucial to obtain stable, functional nanostructures. In this work sodium alginate, carragennan, chitosan, and two galactomannans were characterized in terms of Zp and Z-average, as a function of polysaccharides and NaCl concentrations and pH. The most relevant effects of these factors on Zp and on Z-average were analysed using a 2 3 full factorial design. With a few exceptions, the effect of independent variables on Zp and Z-average values is statistically significant. In general (except for k-carragennan solutions) higher polysaccharide concentrations lead to higher Z-average values; and higher pH values lead to higher Z-average values (except for solutions of chitosan and galactomannan of Gleditsia triacanthos). NaCl addition decreases Z-average. For the galactomannans solutions Zp values were found to be neutral (ranging from −13.7 to −2.1 mV) independently of the combinations of variables used. This work establishes a relationship between important polysaccharides properties and the values of pH, polysaccharide and salt concentrations, thus providing insight on how to control the structure and texture of multinanolayered films in view of their potential application e.g., in the food, pharmaceutical, and cosmetic industries.

This work focused on how different types of oil phase, MCT (medium chain triglycerides) and LCT (long chain triglycerides), exert influence on the gelation process of beeswax and thus properties of the organogel produced thereof. Organogels were produced at different temperatures and qualitative phase diagrams were constructed to identify and classify the type of structure formed at various compositions. The microstructure of gelator crystals was studied by polarized light microscopy. Melting and crystallization were characterized by differential scanning calorimetry and rheology (flow and small amplitude oscillatory measurements) to understand organogels' behaviour under different mechanical and thermal conditions. Fourier transform infrared spectroscopy (FTIR) analysis was employed for a further understanding of oil-gelator chemical interactions. Results showed that the increase of beeswax concentration led to higher values of storage and loss moduli (G′, G″) and complex modulus (G*) of organogels, which is associated to the strong network formed between the crystalline gelator structure and the oil phase. Crystallization occurred in two steps (well evidenced for higher concentrations of gelator) during temperature decreasing. Thermal analysis showed the occurrence of hysteresis between melting and crystallization. Small angle X-ray scattering (SAXS) analysis allowed a better understanding in terms of how crystal conformations were disposed for each type of organogel. The structuring process supported by medium or long-chain triglycerides oils was an important exploit to apprehend the impact of different carbon chain-size on the gelation process and on gels' properties.