Active biobased packaging materials based on poly(lactic acid)-poly(hydroxybutyrate) (PLA-PHB) blends were prepared by melt blending and fully characterized. Catechin incorporation, as antioxidant compound, enhanced the thermal stability, whereas its release was improved by the addition of acetyl(tributyl citrate) (ATBC) as plasticizer. Whereas the incorporation of ATBC resulted in a reduction of elastic modulus and hardness, catechin addition produced more rigid materials due to hydrogen-bonding interactions between catechin hydroxyl groups and carbonyl groups of PLA and PHB. The quantification of catechin released into a fatty food simulant and the antioxidant effectiveness after the release process were demonstrated. The effect of the materials' exposure to a food simulant was also investigated. PHB-added materials maintained their structural and mechanical properties after 10 days in a test medium that represents the worst foreseeable conditions of the intended use. Thus, plasticized PLA-PHB blends with catechin show their potential as biobased active packaging for fatty food.
In this paper, investigations were carried out on catechin-loaded maleic anhydride (MAH)-modified polypropylenes (PP). Two maleic-modified polypropylenes (PPMAH) with different maleic concentrations have been blended with PP and catechin to obtain composites of improved catechin retention with the aim of studying the possible interactions between these grafted polymers with antioxidants, and a secondary interest in developing an active antioxidant packaging. Composite physicochemical properties were measured by thermal analysis (thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and oxidation induction time (OIT)) and infrared spectroscopy studies. Catechin release profiles into food simulants were obtained by HPLC-PDA-QqQ, following European legislation. Antiradical activity of composites was analyzed by the ABTS and DPPH method. The formation of intermolecular hydrogen bonds between catechin and functionalized PP has been confirmed by Fourier transform infrared (FTIR) studies. Besides, a small fraction of ester bonds, formed as a result of a chemical reaction between a fraction of the hydrolyzed anhydride and the catechin hydroxyl groups, is not discarded. OIT results also showed an increase in antioxidant effectiveness caused by the presence of catechin- and maleic-modified PPMAH in the blend formulations. Incorporation of MAH-grafted PP increased substantially the retention rate of catechin, being dependent on the MAH content of the grafted polypropylene. The described interactions between catechin and maleic groups, together with changes in PP morphology in comparison with reference PP explained lower antioxidant release. Besides formulation, antioxidant release was dependent on the type of food, the temperature, and the time.
Several natural matrices were investigated as potential sources of antioxidants to be used as plastic additives. Extracts of four matrices obtained under the same experimental conditions were initially considered: green tea, black tea, Lippia citriodora and Hypericum androsaemum. Both, the antioxidant activity of the extracts and their content in flavanols and quercetin, were compared. The antioxidant activity was determined by DPPH analysis and the phenolic composition by high performance liquid chromatography (HPLC) using ultraviolet (UV) diode array and fluorescence (FL) detectors. Concentration of the flavanols reduced in the same way as their antioxidant activity starting with green tea, through black tea, Hypericum androsaemum, and Lippia citriodora. The performance of polypropylene samples [3553][3554][3555][3556][3557][3558][3559] 2011
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