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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Elabora??o e caracteriza??o de filmes de amido e polpa de acerola por casting, extrus?o termopl?stica e termoprensagem / Elaboration and characterization of starch films with acerola pulp for casting, thermoplastic extrusion and thermopressing

FARIAS, M?nica Guimar?es 06 April 2016 (has links)
CAPES / Due to the environmental impact generated by the continued use of inert material derived exclusively from petroleum, there was an increase in research aimed at developing of films for packaging based on biopolymers, because they are degraded in composting conditions, not harm the environment. Films produced by biopolymer based perform support nutrients functions, preservation of bioactive, improved nutritional and sensory food characteristics of bringing with their quality and shelf life. In this context, the polysaccharides as an alternative because they are able to form solid polymeric matrices. The objective of this study was to develop and characterize flexible biodegradable films from natural polymers from renewable sources (starch), incorporated acerola pulp and clove essential oil (OEC) as antioxidant additives, antimicrobials, sources of vitamin C and carotenoids, prepared by casting process, aiming the choice of the best formulation for production of bioplastics by extrusion and pressing process. The filmogenic solutions were prepared at fixed concentrations of cassava starch (4%), acerola pulp (34.54%) and varying concentrations of glycerol (30; 22,5; 15; 7,5 and 0%) and OEC (0; 7,5, 15, 22,5 and 30%). One step of this study was to evaluate the bacteriostatic ability of the OEC and composite films with him against the bacteria Staphylococcus aureus of Gram-positive group and Salmonella tiphymurium of the Gram-negative group, and the fungus Penicillium sp. and Aspergillus flavus. All formed films were visually transparent and homogeneous. The substitution of glycerol for OEC caused no statistically significant difference in the properties of thickness, water activity (AW) and to water vapor permeability (WVP). The reduced glycerol content, proportional to the increase in concentration of OEC, increased total solids, vitamin C, carotenoids, ?-carotene and antioxidant activity by DPPH and ABTS and the reduction of the moisture content. The reduction of the glycerol content until 15% favored increased stress and strain at tensile and puncture and young modulus, after this limit has shown a drastic reduction in these properties. The desirability function used in the optimization process for selecting the best film produced by casting, to reproduce by extrusion and pressing. The extruded and compressed bioplastic obtained under the same conditions (starch concentration, pulp, glycerol and OEC) that formed by casting, was flexible, visually homogeneous and showed lower values for total solids, tensile deformation, puncture force, vitamin C, carotenoids and ?-carotene contents, and higher values in moisture and antioxidant activity by DPPH. Losses of bioactive were analyzed between each step of the casting process and extrusion, separately. Therefore, the incorporation of pulp acerola and clove essential oil in cassava starch biofilms gave a pronounced protective effect of the bioactive, altering the physical, chemical and mechanical properties. / O impacto ambiental gerado pelo uso cont?nuo de material inerte, oriundo exclusivamente de derivados de petr?leo, tem favorecido o aumento nas pesquisas visando o desenvolvimento de filmes para embalagem a base de biopol?meros, pois estes em condi??es de compostagem s?o reincorporados ao ambiente. Al?m disso, os filmes a base de biopol?meros podem desempenhar fun??es de suporte de nutrientes, preserva??o de bioativos, melhoria das caracter?sticas nutricionais e sensoriais dos alimentos, elevando sua qualidade e vida ?til. Neste contexto, os polissacar?deos apresentam-se como alternativa, pois s?o capazes de formar matrizes polim?ricas cont?nuas. O objetivo deste trabalho foi desenvolver e caracterizar filmes flex?veis biodegrad?veis ativos a partir de amido, incorporados de polpa de acerola e ?leo essencial de cravo (OEC) como aditivos antioxidantes, antimicrobianos, fontes de vitamina C e carotenoides, elaborados pelos processos de casting, extrus?o e termoprensagem. Nos filmes por casting, as solu??es filmog?nicas foram elaboradas em concentra??es fixas de amido de mandioca (4%), polpa de acerola (34,54%) e concentra??es variadas de glicerol (30; 22,5; 15; 7.5 e 0%) e OEC (0; 7,5; 15; 22,5 e 30%) em rela??o ao peso do amido. Sendo, os aditivos glicerol e OEC representados por 30% na base de amido. Uma etapa deste estudo consistiu em avaliar a capacidade antimicrobiana do OEC e dos filmes compostos adicionados deste. Esta avalia??o foi realizada por meio do teste de difus?o em ?gar com as bact?rias Staphylococcus aureus do grupo Gram-positivo e Salmonella tiphymurium do grupo Gram-negativo e dos fungos Penicillium sp. e Aspergillus flavus. Os filmes formados foram visualmente transparentes e homog?neos. A substitui??o do glicerol por OEC n?o provocou diferen?a estatisticamente significativa nas propriedades de espessura, atividade de ?gua (Aw) e permeabilidade ao vapor de ?gua (PVA). A redu??o do teor de glicerol, proporcional ? eleva??o da concentra??o de OEC, aumentou o teor de s?lidos totais, vitamina C, carotenoides totais, ?-caroteno, atividade antioxidante e a redu??o do teor de umidade. A redu??o do teor de glicerol at? 15% favoreceu o aumento da tens?o e deforma??o nos ensaios de tra??o e de perfura??o, bem como do m?dulo de elasticidade, ap?s este limite, foi evidenciada uma redu??o dr?stica nestas propriedades. A fun??o desejabilidade foi utilizada no processo de otimiza??o para sele??o do filme ideal (elevado teor de vitamina C, carotenoide e ?-caroteno, maior resist?ncia e deforma??o nos ensaios de tra??o e perfura??o, elevada capacidade antioxidante e m?dio m?dulo de elasticidade) elaborado por casting, para reprodu??o por extrus?o e prensagem. O biopl?stico extrusado e prensado obtido nas mesmas condi??es (concentra??o de amido, polpa, glicerol e OEC), que o formado por casting, foi flex?vel, visualmente homog?neo e apresentou menores valores para deforma??o na tra??o, for?a na perfura??o, teor de vitamina C, carotenoides, ?-caroteno e capacidade antioxidante por DPPH. Foram analisadas as perdas de bioativos entre cada etapa dos processos casting e extrus?o, separadamente. Possivelmente, a incorpora??o de ?leo essencial de cravo conferiu um pronunciado efeito protetor dos bioativos da polpa de acerola nos biofilmes de amido de mandioca, alterando as propriedades f?sico-qu?micas e mec?nicas.

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