Blendas poliméricas ativas de amido/pectina/micropartícula de lignina por casting e extrusão termoplástica

Abstract

In this work, the incorporation of lignin microparticles in thermoplastic starch films and blends of thermoplastic starch with thermoplastic pectin was evaluated to produce active films to be incorporated into foods with auto-oxidation power. The first stage of the work aimed to evaluate the mechanical action of breaking Kraft lignin into microparticles and the effect on the modification of its properties. In the second step, the interaction of the thermoplastic starch film with different concentrations was evaluated (0%, 1%, 2%, 4% and 6% m/m of ultrasonic lignin microparticles using the casting process. In the third part, the incorporation of lignin microparticles in the blends of thermoplastic starch (TPS) / thermoplastic pectin (TPP) was evaluated in different proportions obtained by extrusion. The results show that the particles were reduced from 6.6μm to 3.1μm and the mechanical process maintained the analyzed properties of the Kraft lignin microparticle, which have antioxidant properties. The structural evaluation by scanning electron microscopy and infrared spectroscopy with Fourier transform demonstrated that in thermoplastic starch films obtained by casting, the increased concentration of ultrasonic microparticles resulted in the formation of aggregates with loss of interaction between the polymers. The films with the incorporation of lignin microparticles had an increase in thermal resistance, showed antioxidant activity and barrier to visible UV light. Only films with 1 and 2% MPLU were not affected by their mechanical properties, which can be used to control the oxidation reaction in food. Those films also showed better thermal resistance, antioxidant activity and the barrier to visible UV radiation. Given the properties analyzed, it was observed that pectin promoted greater mechanical resistance to blends and UV radiation protection - visible. By incorporating lignin microparticles, it was observed that blends with 25% and 50% of thermoplastic pectin achieved an improvement in thermal stability. The blend with 25% of thermoplastic pectin, promoted an increase in elongation to rupture and deformation. This blend also promoted 100% UV-visible radiation protection due to dark brown color. Regarding the permeation properties, films with 25% and 50% of thermoplastic pectin presented low permeability to oxygen (48% and 65%) and the antioxidant property increased from 2.7% to 71.08% and 4.1% to 79,28%, respectively with the incorporation of lignin microparticles. It is concluded that the films obtained by extrusion had better results in the mechanical properties, optics and UV protection - visible, due to the better dispersion of lignin microparticles in the polymer matrix, Polymer blends with 25% concentration of thermoplastic pectin and 4% lignin microparticles are a good alternative for application in foods that are sensitive to oxygen contact and visible - UV radiation.