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Advisor(s)
Abstract(s)
Este trabalho incidiu no estudo da extração de 2,4,6-tricloroanisol (TCA) e de
compostos bioativos da cortiça natural, usando CO2 supercrítico, e também na avaliação
da retenção destes compostos em polímeros molecularmente impressos (MIPs).
Pretendeu-se desta forma contribuir para a criação de conhecimento com aplicação em
indústrias da cortiça, nomeadamente na área do fabrico de rolhas onde a erradicação do
TCA é um problema importante. A valorização de resíduos de cortiça através da extração
e posterior concentração/separação de compostos bioativos, nomeadamente polifenóis,
foi outra vertente explorada nesta contribuição.
Realizaram-se estudos experimentais e de modelação matemática (usando o
método das linhas em MATLAB) sobre a transferência e migração de TCA na cortiça,
considerando como sistema modelo o contacto entre uma solução hidro-alcoólica e a
cortiça. Mostrou-se que a migração do TCA para a cortiça depende de forma crítica da
composição do solvente hidro-alcoólico, devido à influência das interações hidrofóbicas,
o que pode ser útil no projeto de processos de extração de TCA da cortiça.
A extração de TCA da cortiça com CO2 supercrítico foi testada considerando
diferentes combinações entre pressão, temperatura, tempo de extração e presença de cosolvente.
Foi também estudado o tratamento de rolhas de cortiça com CO2 gasoso, para
remoção do ar contido nas células da cortiça, tentando evitar a formação de “papinhos”
nos tratamentos com vapor de água. Os testes realizados incluíram a utilização de rolhas
positivas fornecidas pela corticeira Amorim & Irmãos com medições por SPME-GCECD.
Os resultados obtidos revelam a migração substancial do TCA das zonas interiores
da rolha para a sua superfície, indicando que o tratamento das rolhas não deverá incidir
em zonas com profundidade superior a cerca de 3 mm.
Mostrou-se que a utilização de MIPs apresenta vantagens importantes na
valorização de polifenóis presentes em extratos de cortiça, nomeadamente em
comparação com outros adsorventes comerciais (ex. DAX8, XAD4 e XAD7HP). De
facto, utilizando MIPs sintetizados com 4-vinilpiridina e análises por LC/MS/DAD,
comprovou-se que é possível isolar o ácido elágico (ex.) presente em extratos de cortiça.
This work was devoted to the extraction of 2,4,6-trichloroanisole (TCA) and bioactive compounds from natural cork, using supercritical CO2, and also to the assessment of the retention of these compounds in molecularly imprinted polymers (MIPs). It is intended to contribute for the development of knowledge with application in cork industries, namely in the cork stoppers fabrication, where the eradication of TCA is a critical problem. The valorization of cork residues through the extraction and subsequent concentration/separation of bioactive compounds, namely polyphenols, was other research line here explored. The transfer and migration of TCA in the cork was experimentally and theoretically studied (through mathematical modeling in MATLAB using the method of the lines) with the system model concerning the contact between a hydro-alcoholic solution and the cork. It was shown that the migration of TCA to the cork strongly depends on the composition of the hydro-alcoholic solution, due to hydrophobic effects, which can be useful in the designing of processes to extract TCA from cork. The extraction of TCA from cork with supercritical CO2 was performed considering different combinations between pressure, temperature, extraction time and presence of a co-solvent. The treatment of cork stoppers with gaseous CO2 was also considered for the removal of air in the cork cells, trying to avoid the formation of surface defects with the hot steam treatments. These studies included the use of positive corks stoppers, provided by the company Amorim & Irmãos with measurements of the TCA concentration using SPME-GC-ECD. The results obtained show the substantial migration of TCA from inner region to the surface of the corks stoppers, allowing estimating that the cork stopper treatment should not exceed c.a. 3 mm in depth. It was shown that MIPs present important advantages comparatively to other commercial adsorbents (e.g. DAX8, XAD4 and XAD7HP) in the framework of the valorization of polyphenols present in cork extracts. Indeed, using MIPs synthesized with 4-vinylpyridine and LC/MS/DAD analyses, was proved that is possible the isolation of ellagic acid present in cork extracts.
This work was devoted to the extraction of 2,4,6-trichloroanisole (TCA) and bioactive compounds from natural cork, using supercritical CO2, and also to the assessment of the retention of these compounds in molecularly imprinted polymers (MIPs). It is intended to contribute for the development of knowledge with application in cork industries, namely in the cork stoppers fabrication, where the eradication of TCA is a critical problem. The valorization of cork residues through the extraction and subsequent concentration/separation of bioactive compounds, namely polyphenols, was other research line here explored. The transfer and migration of TCA in the cork was experimentally and theoretically studied (through mathematical modeling in MATLAB using the method of the lines) with the system model concerning the contact between a hydro-alcoholic solution and the cork. It was shown that the migration of TCA to the cork strongly depends on the composition of the hydro-alcoholic solution, due to hydrophobic effects, which can be useful in the designing of processes to extract TCA from cork. The extraction of TCA from cork with supercritical CO2 was performed considering different combinations between pressure, temperature, extraction time and presence of a co-solvent. The treatment of cork stoppers with gaseous CO2 was also considered for the removal of air in the cork cells, trying to avoid the formation of surface defects with the hot steam treatments. These studies included the use of positive corks stoppers, provided by the company Amorim & Irmãos with measurements of the TCA concentration using SPME-GC-ECD. The results obtained show the substantial migration of TCA from inner region to the surface of the corks stoppers, allowing estimating that the cork stopper treatment should not exceed c.a. 3 mm in depth. It was shown that MIPs present important advantages comparatively to other commercial adsorbents (e.g. DAX8, XAD4 and XAD7HP) in the framework of the valorization of polyphenols present in cork extracts. Indeed, using MIPs synthesized with 4-vinylpyridine and LC/MS/DAD analyses, was proved that is possible the isolation of ellagic acid present in cork extracts.
Description
Keywords
CO2 supercrítico Polímeros molecularmente impressos (MIPs) Polifenóis 2,4,6-tricloroanisol (TCA)