Limonina em citrinos: análise, bioconversão e bioactividade

• Author(s): Silva, Susana Isabel Coelho Vieira da
• Date: 2010
• Persistent ID: http://hdl.handle.net/10451/2587
• Origin: Repositório da Universidade de Lisboa
• Subject(s): Teses de mestrado
• Document Type: Master thesis
• Language: Portuguese
• Advisor(s): Ribeiro, Maria Henriques Lourenço, 1958-; Ferreira-Dias, Suzana
• Contributor(s): Repositório da Universidade de Lisboa

Description

Tese de mestrado, Controlo da Qualidade e Toxicologia dos Alimentos, Universidade de Lisboa, Faculdade de Farmácia, 2010

Os citrinos são aceites pelo seu valor nutritivo e medicinal, assim como por providenciarem um sabor característico a uma grande variedade de produtos alimentares, o que lhes confere uma ampla aceitação e popularidade no seio da indústria de produção alimentar. Contudo, um problema global na indústria dos citrinos é o desenvolvimento de um sabor amargo no sumo e produtos de citrinos após a extracção do sumo. O sabor amargo ocorre em algumas variedades de laranjas, toranjas e limões, com significativo impacto comercial negativo. A conversão da limonina monolactona a limonina tem sido referenciada como a principal razão para o desenvolvimento tardio do sabor amargo em sumos de citrinos. Neste trabalho, o objectivo centrou-se na avaliação da remoção selectiva da limonina de sumo de laranja por adsorção a diferentes resinas poliméricas neutras e por formação de complexos de inclusão com ciclodextrinas. O método HPLC utilizado foi validado para o composto em estudo, através da aplicação de vários testes estatísticos, que permitiram definir o intervalo de linearidade, a gama de trabalho, os limiares analíticos, a precisão e a estimativa da incerteza do método de ensaio. As resinas sintéticas neutras utilizadas foram as seguintes: Amberlite XAD-8, XAD-16N e XAD-1600. O estudo foi realizado em microescala. Os melhores resultados foram obtidos para a resina XAD-18 com valores de adsorção superior a 80 %. Não se observou adsorção significativa de açúcares, pigmentos e vitamina C. Os modelos de isotérmicas de adsorção de Freundlich e Langmuir foram ajustados aos dados experimentais de adsorção da limonina às resinas utilizadas. As ciclodextrinas são oligómeros cíclios que têm vindo a ganhar grande aceitação por parte da indústria alimentar. A β-ciclodextrina e γ- ciclodextrina foram testadas como método alternativo à remoção de compostos amargos de sumos e produtos de citrinos. A razão de 1:1 (Sumo:ciclodextrina) originou uma inclusão de 92,5 % e de 82 % de limonina do sumo. A limonina apresenta também um variado leque de actividades biológicas, principalmente actividade anti-inflamatória. Esta acção foi avaliada através da medição do edema induzido da pata do rato. A limonina complexada em ciclodextrinas originou uma redução do edema (≈50%) semelhante no sumo processado e não processado. Citrus fruits are accepted for their nutritive and medicinal value as well as for providing distinctive flavor to a wide variety of food products, making it very popular among food product designers. However, a worldwide major problem in the citrus industry is the formation of bitterness in citrus juice and products after juice extraction. This bitterness occurs in certain varieties of oranges, grapefruits and lemons showing a significant negative commercial impact. The conversion of limonate-A-ring lactone into limonin has been reported as the reason for delayed bitterness of citrus juice. This reaction proceeds under acidic conditions below pH 6.5 and is accelerated by the enzyme limonin-D-ring lactone hydrolase. The presence of limonin and nomilin has been the main cause of delayed bitterness of citrus fruits. In this work, the objective was to investigate the selective removal of limonin from orange juice by batch adsorption to different microstructured resins. Since the removal of reducing sugars, pigments and vitamin C may also occur, the eventual adsorption of these compounds was also investigated. In addition, limonin presents a wide range of biological activities, mainly concerning anti-inflamatory properties. Limonin's anti-inflamatory ability was assayed by measurement of induced rat paw edema. The used HPLC method was validated through the application of several statistical methods wich allow defining the linearity range, working ranges, analytical limits, precision and the uncertainty estimation of the analytical assay for the studied compound. The following synthetic neutral resins, were tested: Amberlite XAD-8, XAD-16N and XAD-1600. The experiments were performed in a microscale, using 24 wells microplates. No significant adsorption of sugars, pigments and vitamin C to the resins was observed. Both Freundlich and Langmuir isotherm models were fitted to the experimental data of adsorption of limonin to the resins used. Cyclodextrins are cyclic oligomers that have been gaining wider acceptance in the food industry as food additives, for stabilization of flavours, for elimination of undesired tastes or other undesired compounds, mainly due to their ability to form inclusion complexes. β-ciclodextrin and γ-ciclodextrin were test as an alternative method to remove bitter compounds from citrus juice and products.

Citrus fruits are accepted for their nutritive and medicinal value as well as for providing distinctive flavor to a wide variety of food products, making it very popular among food product designers. However, a worldwide major problem in the citrus industry is the formation of bitterness in citrus juice and products after juice extraction. This bitterness occurs in certain varieties of oranges, grapefruits and lemons showing a significant negative commercial impact. The conversion of limonate-A-ring lactone into limonin has been reported as the reason for delayed bitterness of citrus juice. This reaction proceeds under acidic conditions below pH 6.5 and is accelerated by the enzyme limonin-D-ring lactone hydrolase. The presence of limonin and nomilin has been the main cause of delayed bitterness of citrus fruits. In this work, the objective was to investigate the selective removal of limonin from orange juice by batch adsorption to different microstructured resins. Since the removal of reducing sugars, pigments and vitamin C may also occur, the eventual adsorption of these compounds was also investigated. In addition, limonin presents a wide range of biological activities, mainly concerning anti-inflamatory properties. Limonin's anti-inflamatory ability was assayed by measurement of induced rat paw edema. The used HPLC method was validated through the application of several statistical methods wich allow defining the linearity range, working ranges, analytical limits, precision and the uncertainty estimation of the analytical assay for the studied compound. The following synthetic neutral resins, were tested: Amberlite XAD-8, XAD-16N and XAD-1600. The experiments were performed in a microscale, using 24 wells microplates. No significant adsorption of sugars, pigments and vitamin C to the resins was observed. Both Freundlich and Langmuir isotherm models were fitted to the experimental data of adsorption of limonin to the resins used. Cyclodextrins are cyclic oligomers that have been gaining wider acceptance in the food industry as food additives, for stabilization of flavours, for elimination of undesired tastes or other undesired compounds, mainly due to their ability to form inclusion complexes. β-ciclodextrin and γ-ciclodextrin were test as an alternative method to remove bitter compounds from citrus juice and products.