Role of constituents on structure and properties of polysaccharides proteins edible films.

As biodegradable film, edible films and coatings can be a good answer to environmental pollution requirement. However, due to its hydrophilic nature they cannot fully replace the polymer film, but they can partially satisfy the legislation requirements. By acting as mass transfer barriers, edible film and coating can control moisture, oxygen, carbon dioxide, lipid, flavour and aroma transfer either between food components or to/from the atmosphere surrounding the food. In fact, respect to biodegradable packaging, they can be applied on the food and consumed with it. This can reduce the requirements of the synthetic polymer. Thus, the amount of synthetic packaging is reduced, recyclability is increased, and the need of synthetic laminates is diminished. Biopolymers are quite abundant in nature and have previously been regarded as surplus or waste. In order to improve film or coating properties biopolymers must be combined in new and creative ways. For this reason it is interesting to investigate different matrices, parameters and factors that may influence the properties of the films in order to optimize the performance of edible films and coatings and to understand the relationships between structure and properties. The production of edible film by combining various polysaccharides, proteins and lipid is considered beneficial because there is the advantage of the properties of each compound and the synergy between them. The attributes that each component contributes to overall film properties are different too. The aim of this work was to investigate the effect of compounds on structure and functional properties of hydrocolloids based films. The results will help to develop a coating system with specific properties, such as solubility, barrier and mechanical properties, to control physiological, microbiological and physicochemical changes in food products, with an improvement of the food quality and an increasing of their shelf-life. To reach this objective the research was articulated in three study cases. I STUY CASE Effect of rosemary oil on functional properties of hydroxyl propyl methyl cellulose films. Edible films based on hydroxyl propyl methylcellulose (HPMC) obtained with different concentrations of rosemary oil (0.0, 0.4, 0.7, 1.0, 2.0) were prepared. In order to study the impact of the incorporation of rosemary oil into the HPMC matrix, microscopy analysis mechanical properties, and water vapour permeability (WVP) were evaluated. Results showed the structure of HPMC film was affect by rosemary oil concentration. Probably, most oil had migrated toward the evaporation surface. This phenomena was most evident to maximum oil concentration for 2%HPMC film for low viscosity of HPMC solution. For dynamical mechanical analysis, it must be highlighted that for these films an higher variability of the data was measured respect to film at 2% of HPMC, thus from a statistically point of view not significant differences can be highlighted among samples at different oil concentration. WVP of HPMC films increased as increased HPMC concentration for increased of hydrophilic groups. Rosemary oil improve water barrier properties only to 0.4% concentration oil of 6% HPMC films. II STUDY CASE: Structure and properties of Hydroxy propyl methyl cellulose-sodium caseinate film cross-linked by Transglutaminase The objective of the present work was to study the structure and the functional properties of Hydroxypropil methyl cellulose (HPMC)-sodium caseinate (SC) edible films cross linked with TGase. SDS-PAGE, scanning electronic microscopy and dynamical mechanical analysis were performed to investigate the structure of the films. Film performance were studied by means of solubility test, thickness, mechanical properties and water vapour permeability. Results show that structure and functional properties of HPMC/CS films were affected by the film composition. In particular, the number of cross-links within the blend edible films is function of HPMC/SC ratio and increased by increasing the protein concentration, but only for HPMC concentration less than 50%. The cross linked structure in presence of protein can enhance blend film solubility but only at specific ratio HPMC/SC, maybe due to immiscibility lacunas. Mechanical properties confirmed the positive role of polysaccharides on the film stiffness, but the negative effect on film extensibility. In contrast, the different ratio of HPMC/CS film did not affect the permeability to water vapour of the films, showing that it is the hydrophilic nature of the polymer that play the major role in determine the barrier properties of the films. III STUDY CASE Food application of sodium caseinate cross linked with trasglutaminase edible film: oil absorption reduction on French fried potatoes The objective of the present work was to assess the oil barrier properties of Sodium caseinate film coated on potato surface. Sodium caseinate coating at two concentration were prepared and applied on the potato surface by immersion for 5 minute. The product was dried to allow the film formation on the food surface. Coated and uncoated potato were fried for 3 minute in oil at 190°C and then the absorbed oil was determined by extraction with n-hexane. Preliminary results showed that the sodium caseinate film to concentration tested did not reduce oil absorption during frying process. Because oil absorption depends by several factor including formulation coating and the homogeneity of the coated surface, we hypothesized that was need to optimized coating formulation