Termodinâmica de interação entre betacaroteno e proteínas do leite
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Data
2015-11-16
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Universidade Federal de Viçosa
Resumo
A cor é um atributo sensorial que influencia de forma decisiva o julgamento dos consumidores quanto a determinado tipo de alimento. Por esta razão, as indústrias alimentícias possuem uma frequente preocupação com a adição de corantes aos seus produtos, de forma a torna-los mais atrativos aos consumidores. Duas classes distintas de corantes estão disponíveis para uso em alimentos, os sintéticos e os naturais. Os corantes sintéticos são mais frequentemente utilizados em virtude de algumas vantagens apresentadas por estes em relação aos naturais, como maior estabilidade frente a diferentes fatores e maior solubilidade em soluções aquosas. Entretanto, estudos toxicológicos têm apontado estes corantes como potenciais causadores de problemas à saúde dos consumidores. Estes estudos, bem como a crescente preocupação dos consumidores com aspectos relacionados à saúde e também medidas legislativas têm motivado a substituição dos corantes sintéticos por aqueles obtidos a partir de fontes naturais, os quais apresentam menores evidências de danos à saúde dos consumidores. Por outro lado, a utilização de corantes naturais em formulações alimentícias ainda é bastante limitada devido principalmente à menor estabilidade e solubilidade destes na matriz alimentícia, por ser tratarem, em geral, de compostos lipofílicos. As proteínas do leite possuem um importante papel no transporte de moléculas hidrofóbicas, tais como corantes. Diante disso, objetivou-se estudar a interação a nível molecular entre o betacaroteno, um corante natural, e as proteínas lácteas albumina sérica bovina (em suas conformações nativa e desnaturada) e beta-caseína, através de técnicas sensíveis utilizadas em estudos de interações. Os resultados obtidos através da técnica espectroscopia de fluorescência mostraram que em pH 7,0 concentrações crescentes de betacaroteno reduziram a intensidade de fluorescência de ambas as proteínas, beta-caseína e albumina sérica bovina, e que o mecanismo de extinção de fluorescência foi principalmente estático. As constantes de interação associadas a formação do complexo entre o betacaroteno e as proteínas lácteas variaram com as temperaturas estudadas entre 8,43x104 e 4,20x107 L mol-1 para BSA nativa, 1,11x102 e 5,05x102 L mol-1 para BSA desnaturada e entre 3,34x101 e 2,457x103 L mol-1 para beta-caseína. A estequiometria de formação do complexo (betacaroteno:proteína) também variou entre as proteínas, sendo 1:1 para BSA nativa, 1:3 para BSA desnaturada e 1:2 para beta-caseína. Os valores da variação da energia livre de Gibbs padrão de formação do complexo variaram com a temperatura e foram negativos para todos os sistemas estudados. Entretanto, os valores deste parâmetro obtidos para a beta-caseína foram inferiores em relação aqueles obtidos para a BSA. A formação do complexo em todos os casos foi dirigida pela entropia do sistema. Resultados de fluorescência obtidos no pH 5,0 para a albumina sérica bovina mostraram que a interação entre esta proteína e o betacaroteno foi praticamente constante, provavelmente por questões relacionadas a conformação e distribuição de grupos carregados da proteína neste valor de pH. A estabilidade à luz do corante foi avaliada na presença e na ausência de albumina sérica bovina e beta-caseína e os resultados mostraram que ambas as proteínas protegeram o corante da degradação ocasionada pela luz. Os resultados gerais obtidos apontaram para a utilização eficiente das proteínas lácteas no transporte e estabilização do betacaroteno em sistemas alimentícios.
The color is a sensory attribute that influence decisively the judgment of consumers in certain type of food. For this reason, the food industries have a common concern with the addition of coloring to their products in order to make them more attractive to consumers. Two distinct classes of dyes are available for use in foods, synthetic and natural. Synthetic dyes are most often used due to certain advantages presented by these in relation to natural, such as increased stability due to different factors, solubility in aqueous solutions, providing a wide variety of colors and lower production costs. However, toxicological studies have pointed to these dyes as potential troublemakers to the health of consumers, ranging from allergies to cancer development. These studies as well as the growing consumer concern with health- related characteristics and also legislative measures have motivated the replacement of synthetic dyes by those obtained from natural sources, which, although also present drawbacks, have been used for many years with minor evidence of harm to the health of consumers. The use of natural colorants in food formulations is very limited due mainly to decreased stability and solubility thereof in the food matrix, to be treat in general, of lipophilic compounds. Milk proteins have an important role in the transport of hydrophobic molecules such as dyes. The research objective was to study the interaction at the molecular level between beta-carotene, a natural dye, bovine serum albumin and beta-casein, through sensitive techniques used in interaction studies. The results obtained by fluorescence spectroscopy technique showed that at pH 7.0 increasing concentrations of beta-carotene reduced the fluorescence intensity of both proteins, beta-casein and bovine serum albumin, and the fluorescence quenching mechanism is mainly static. Interaction constants associated with complex formation between the beta-carotene and dairy proteins with temperatures studied ranged between 8,43x104 and 4,20x107 L mol-1 for native, BSA, between 1,11x102 and 5,05x102 L mol-1 for denatured BSA and between 3,34x101 and 2,457x103 L mol-1 for beta-casein. The stoichiometry of the complex formation (beta-carotene:protein) also varied between proteins, being 1:1 to native BSA, 1:3 to denatured BSA and 1:2 for beta-casein. The values of variation of the standard Gibbs free energy of complex formation varied according to temperature and were negative for all systems studied. However, the values of this parameter obtained for beta casein were lower compared to those obtained for BSA. The formation of the complex in all cases was driven by the entropy of the system. Fluorescence results obtained in the pH 5.0 to bovine serum albumin showed that the interaction between this protein and beta-carotene was almost constant, probably issues the conformation and distribution of charged groups of the protein at this pH value. The dye light stability was assessed in the presence and absence of bovine serum albumin and beta-casein and the results showed that both proteins dye protected from degradation caused by light. The overall results obtained pointed to the efficient use of milk protein in the transport and stabilization of beta-carotene in food systems.
The color is a sensory attribute that influence decisively the judgment of consumers in certain type of food. For this reason, the food industries have a common concern with the addition of coloring to their products in order to make them more attractive to consumers. Two distinct classes of dyes are available for use in foods, synthetic and natural. Synthetic dyes are most often used due to certain advantages presented by these in relation to natural, such as increased stability due to different factors, solubility in aqueous solutions, providing a wide variety of colors and lower production costs. However, toxicological studies have pointed to these dyes as potential troublemakers to the health of consumers, ranging from allergies to cancer development. These studies as well as the growing consumer concern with health- related characteristics and also legislative measures have motivated the replacement of synthetic dyes by those obtained from natural sources, which, although also present drawbacks, have been used for many years with minor evidence of harm to the health of consumers. The use of natural colorants in food formulations is very limited due mainly to decreased stability and solubility thereof in the food matrix, to be treat in general, of lipophilic compounds. Milk proteins have an important role in the transport of hydrophobic molecules such as dyes. The research objective was to study the interaction at the molecular level between beta-carotene, a natural dye, bovine serum albumin and beta-casein, through sensitive techniques used in interaction studies. The results obtained by fluorescence spectroscopy technique showed that at pH 7.0 increasing concentrations of beta-carotene reduced the fluorescence intensity of both proteins, beta-casein and bovine serum albumin, and the fluorescence quenching mechanism is mainly static. Interaction constants associated with complex formation between the beta-carotene and dairy proteins with temperatures studied ranged between 8,43x104 and 4,20x107 L mol-1 for native, BSA, between 1,11x102 and 5,05x102 L mol-1 for denatured BSA and between 3,34x101 and 2,457x103 L mol-1 for beta-casein. The stoichiometry of the complex formation (beta-carotene:protein) also varied between proteins, being 1:1 to native BSA, 1:3 to denatured BSA and 1:2 for beta-casein. The values of variation of the standard Gibbs free energy of complex formation varied according to temperature and were negative for all systems studied. However, the values of this parameter obtained for beta casein were lower compared to those obtained for BSA. The formation of the complex in all cases was driven by the entropy of the system. Fluorescence results obtained in the pH 5.0 to bovine serum albumin showed that the interaction between this protein and beta-carotene was almost constant, probably issues the conformation and distribution of charged groups of the protein at this pH value. The dye light stability was assessed in the presence and absence of bovine serum albumin and beta-casein and the results showed that both proteins dye protected from degradation caused by light. The overall results obtained pointed to the efficient use of milk protein in the transport and stabilization of beta-carotene in food systems.
Descrição
Palavras-chave
Corantes em alimentos, Caroteno, Albumina, Beta-caseína, Leite - Proteínas, Termodinâmica
Citação
SILVA, Carla Eduarda Ladeira. Termodinâmica de interação entre betacaroteno e
proteínas do leite. 2015. 78f. Dissertação (Mestrado em Ciência e Tecnologia de Alimentos) - Universidade Federal de Viçosa, Viçosa. 2015.