Orientador: Prof. Dr. Antonio R. G. Monteiro

Data da Defesa: 19/04/2013



 INTRODUCTION. Biodegradable packaging assets have been identified as the solution to minimize environmental impacts and improve the quality of food preservation. So develop biodegradable polymers that have made possible the cost is necessary for development of these packages. Starch, despite abundant and cheap is very hygroscopic which prevents the production of films that product only. Thus, appears as an alternative development of the blends of polymers, combining polymer from renewable sources and biodegradable synthetic polymers such as starch and poly (butylene adipate-co-terephthalate) (PBAT). Delaying lipid oxidation is one of the positive interactions that can check the packaging to food. The application of antioxidant compounds extracted from plant waste such as bark and avocado already widely known antioxidants like tocopherol becomes the way for exploration of technologies involving the environment and food quality.
AIMS. The aim of this study was to evaluate the antioxidant capacity and characterize films made from blends of thermoplastic starch (TPS)/poly (butylene adipate-co-terephthalate) (PBAT) added antioxidants tocopherol and avocado peel extract at concentrations determined from an experiment.
MATERIAL AND METHODS. The bark extract avocado (ExA) was obtained through an ethanolic extraction. The films were made by blow extrusion. Five different films were prepared, FC, the control formulation, F1 formulation with 0,6% ExA, F2 formulation with 0,8% TOCO 70 (70% tocopherol and 30% soybean oil), F3 the formulation with 0,6% and 0.8% ExA TOCO 70 and F4 formulation with 0,3% and ExA and 0,4% TOCO 70. The antioxidant capacity (AC) of antioxidant compounds, as well as the films was determined by the DPPH •. The examination was characterized by UPLC-ESI (-) MS (Ultra-high performance liquid chromatography coupled to electrospray ionization mass spectrometry in the negative ion mode). For characterization of the movies was constructed sorption isotherm at 25 ° C, determined water vapor permeability (WVP), thickness (δ), density (ρ), solubility (β) and diffusion (Dw) coefficient. The tensile strength (MPa), elongation (%), and elastic modulus (MPa) were determined from analyzes performed in texturometer Stable Micro (model TA.TX2i, England). The microstructure of the fracture surfaces of the films was evaluated by scanning electron microscopy.
RESULTS AND DISCUSSION. Through analysis of UPLC-ESI (-) MS detects the presence of the following compounds antioxidants in ExA: citric acid (133,15 ± 9,53 mg 100-1 extract g), malic acid (74,68 ± 2,12 mg 100-1 g extract), tartaric acid (11,77 ± 0,14 mg 100-1 g extract), catechin hydrate (82,08 ± 3,27 mg 100-1 g extract) and epicatechin (62,39 ± 2,53 mg 100-1 g extract).
The antioxidant capacity of ExA and TOCO 70 were approximate 187,65 ± 7,60 mmol ET/g of sample and 162,09 ± 8,47 mmol ET/g sample respectively. The formulation F3 that showed the best antioxidant activity, this formulation containing the highest percentage of ExA and TOCO 70, it showed an increase of 99,4% compared to the CA of FC. The formulation F4 (0,4% TOCO 70 and 0,3% of ExA) showed no significant difference in the formulation F2, with 0,8% TOCO 70. The formulation F1 (0,6% ExA) had the lowest CA films produced from the compounds with antioxidant. But F1 contains 1/4 to less than an antioxidant that the formulation F2, probably soon be applied the same quantity of ExA and TOCO 70 formulations in the CA would not present significant difference. No effect was observed between the proportional
increases in the addition of an antioxidant and improves the antioxidant capacity of the films.
The sorption isotherm is an important tool to evaluate the interference of different relative humidity in the hydrophilicity of the film and from it we can see that the film FC absorbed 34,25% more water compared to F2, 20,69% compared F3, 11,10% compared to 10,00% in F4 and F1 in relation to relative humidity above 75%, so antioxidants helped in reducing water absorption. The film F2, with 0,8% TOCO-70 showed the lowest water absorption when compared to other formulations, which demonstrates the TOCO 70 had a strong influence on the hydrophilicity of the film, this probably already have in your makeup soybean oil which assists in sealing of the structure.
The formulations with antioxidant had lower values of permeability to water vapor (WVP) when compared to FC. The formulation F2 with 0,8% TOCO 70 showed the lowest solubility and diffusion coefficient. This shows that the EXA and TOCO 70 acted as compatibilizer of the films, helping the interaction of the polymers, enabling the formation of a more compact structure with little space for movement of the molecules as shown by the diffusion coefficient and less hydrophilicity as shown in solubility coefficient. In addition to the presence of antioxidants including improved flexibility of the film, since the control formulation showed the greatest thickness.
Regarding the mechanical properties was notorious increased tensile strength and elongation of the films containing ExA in its composition. In relation to the elastic modulus formulations showed no significant difference between them.
In view of the microstructure and fracture surface was not observed phase separation, gelatinized starch granules which demonstrates a good interaction between the compounds of the films. However, the image of FC demonstrates greater irregularity in the fracture when compared with the other formulations, may be related to the fact that antioxidant compounds confer greater elasticity to the movies.
CONCLUSIONS. The addition of antioxidants in the formulation of biodegradable films promoted an improvement in antioxidant capacity of the films, besides having improved structural characteristics, because this helped reduce permeability to water vapor, increased tensile strength and increased elongation. Among the formulations that gained prominence in the antioxidant capacity was F3 which contains in its formulation the greatest amount of antioxidant compounds. It should be noted that the extract from the bark of avocados improved the mechanical properties of tension and elongation and retained more ordered structure of the films. This result is very interesting because it confirms that the application of bark extract of avocado and tocopherol in packaging can contribute to sustainability in the production of biodegradable packaging and active.
Key words: Active packaging, biodegradable pack

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