Development of new material formulations to produce active films for food packaging
Creators: name: Attianese, Ilaria
Publisher: name: Università degli Studi di Napoli Federico II
Year: 2013

description: Packaging is one of the most important technological steps of food preservation. Microbial growth and oxidation reactions occurring on food surface are two of the main causes of deterioration of fresh and processed food products. Traditional food packaging generally protect foodstuff from external influences. Whereas active packaging systems interact with the food permitting the extension of their shelf-life and the maintenance, or even the improvement of their quality and sensorial features.
The main objective of this thesis is the attainment of knowledge related to the development of new material formulations for food packaging by using suitably modified inorganic nanoparticles in order to obtain a controlled release system of active substances and to improve active film physical and gas barrier performances.
As far as antioxidant active films is concerned, the aim of the work is the development of innovative films containing natural -tocopherol adsorbed onto functionalised and not functionalised mesoporous silica particles (SBA-15; SBA-15+APTES) in order to protect it during LDPE film manufacture and to be able to control its release rate. The synthesized mesoporous powders were characterized by means of X-ray diffraction and N2 adsorption/desorption at 77 K. Powders loaded with tocopherol were characterized by infrared spectroscopy and thermogravimetric analysis. Results show that the maximum of the pore size distribution reduces from 90 Å for purely siliceous SBA-15 to 73 Å for amino-functionalized SBA-15. Infrared analysis shows that tocopherol interacts with the amino groups of functionalized SBA-15. It has been also proven that circa 40% and 30% of tocopherol is loaded into SBA-15 and SBA-15+APTES respectively. Release tests performed using 96% v/v ethanol as fatty food stimulant show that the tocopherol diffusivity of films containing functionalized mesoporous silica decreased of about 50% with respect to films containing free tocopherol, as. This is due to the decrease in the pore size and to the increase in diffusion resistance caused by the functionalization of the internal pore walls with the amino groups. Moreover, the oxygen radical absorbing capacity (ORAC) assay of the produced active polymer films proved the antioxidant effectiveness of tocopherol released from samples after manufacturing process.
As far as antimicrobial activity is concerned, silver montmorillonite clays have been increasingly investigated as germicidal, bactericidal, antifungal, and antiseptic components in different food packaging formulation. The aim of this thesis is the development of a new class of antimicrobial systems in which the inorganic phyllosilicate clays (MMT) have been used as support for silver nanoparticles (AgNPs) . The Ag-MMT filler consists of nanometric metallic silver and oxides particles (size in the range 2-40nm) preferentially located on the surface of MMT single lamellae as the UV adsorption and FT-IR spectra showed. Antimicrobial bionanocomposites have been obtained by solution casting of AgMMT particles into chitosan, one of the most interesting biopolymers obtained from natural sources. The combined effect of glycerol and AgMMT particles on the thermal, structural and barrier properties of the obtained bionanocomposites was investigated. In fact, the plasticizer and the silver ions as well as the surface of metallic particles exert a combined effect which allows a reduction of the liquid water uptake and water permeability with respect to neat chitosan. Indeed, X.Ray results  revealed that Ag-MMT particles result partially intercalated by chitosan macromolecules although it cannot be excluded in such an extent the exfoliation due to the collapse of MMT structure during the preparation of the active filler. Moreover, considering that the antibacterial mechanism of silver is mainly related to the action of silver ions and metallic AgNPs, the silver release kinetics from bionanocomposites in water at 25°C were also investigated. 
In conclusion, samples of purely siliceous and amino-functionalized SBA-15 mesoporous silica were successfully used as α-tocopherol carriers for the production of active LDPE polymer films. In fact, active polymer films containing the functionalized carrier showed a slower tocopherol release when compared to samples containing free tocopherol and tocopherol loaded onto purely siliceous substrate. Whereas, for antimicrobial active film,. the silver supporting nanoparticles, Ag-MMT, contribute to modulate the release kinetics of silver ions from bionanocomposite films over a longer time interval (up to 20 days). This is of paramount importance for the production of active films to be used as food packaging materials or potentially as biomaterials.