Comportamento reológico da goma Tara (Caesalpinia spinosa) e formação de géis em combinação com a goma Xantana
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Data
2020-01-31
Autores
Huamaní Meléndez, Víctor Justiniano
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
Os polissacarídeos são empregados na indústria de alimentos pela capacidade de modificar as propriedades reológicas, estabilizar emulsões ou partículas suspensas ou como gelificante. Dentre eles encontra-se a goma Tara (TG), obtida das sementes da Tara (Caesalpinia spinosa), ainda pouco usada na indústria de alimentos, principalmente devido ao pouco conhecimento sobre as suas propriedades funcionais, e escassez de pesquisas sobre as interações com outros polímeros e compostos. Os objetivos da pesquisa foram compreender melhor a estrutura da goma Tara, propriedades reológicas, interações moleculares em solução aquosa, em mistura com proteínas do leite e ainda sobre a formação de géis em mistura com a goma Xantana (XG), visando aplicações como o desenvolvimento de novas texturas e formulação de produtos alimentícios, cosméticos ou farmacêuticos. Foi utilizada a TG comercial de três origens diferentes, as quais foram purificadas por precipitação com isopropanol e avaliadas suas propriedades físico-químicas, reológicas e aspectos estruturais das galactomananas. Para a avaliação estrutural e composição monossacarídea foram usadas técnicas de Espectroscopia no Infravermelho por Transformada de Fourier (FT-IR) e Ressonância Magnética Nuclear (RMN). As propriedades físico-químicas foram obtidas a partir da viscosidade intrínseca determinada por viscosimetria capilar e as propriedades reológicas foram determinadas mediante viscosímetro rotacional. A estabilidade de misturas aquosas de TG com caseinato de sódio (NaCas) e concentrado proteico de soro de leite (WPC), assim como o comportamento reológico foram avaliados usando a metodologia de superfície de resposta, tomando como fatores as concentrações de NaCas, WPC e TG. As variáveis resposta foram a viscosidade a taxa de deformação nula (𝜂��0) e o tempo de relaxação (𝜆��). Os géis formados com a mistura aquosa de TG e XG foram avaliados, especialmente quanto às suas propriedades mecânicas. A composição monossacarídea das galactomananas de TG resultou ser dependente da origem, apresentando relação manose:galactose de 1,54–1,85. A viscosidade intrínseca da TG foi influenciada pelo efeito combinado de pH-temperatura e a adição de sal. Em concentrações diluídas apresentou comportamento dilatante e em regimes semidiluído e concentrado mostrou-se pseudoplástico (viscoelástico), verificando-se predomínio do componente viscoso nas baixas frequências. As soluções de TG e proteínas do leite apresentaram condição metaestável pelo aumento na viscosidade, variando os mecanismos de estabilização para as soluções de TG-NaCas e TG-WPC. Apresentaram comportamento pseudoplásico, observando-se interação entre a TG e as proteínas estudadas, expressa pelo aumento da 𝜂��0 e 𝜆�� na maior concentração de goma. Encontrou-se também sinergismo positivo na mistura de TG e XG, com aumento significativo do caráter sólido do gel e o incremento na força do gel formado.
Polysaccharides are used in the food industry due to their ability to modify rheological properties, stabilize emulsions or suspended particles or as a gelling agent, including Tara gum (TG) obtained from Tara seeds (Caesalpinia spinosa), which has limited used in the food industry, mainly due to restricted knowledge about their functional properties, and few research on the interactions with other polymers and compounds. The aim of this study is to gain understanding of Tara gum structure, rheological properties, molecular interactions in aqueous solution, in mixture with milk proteins and the formation of gels with Xanthan gum (XG), aiming at applications such as the development of new textures and new formulations for food beverage, cosmetic or pharmaceutical products. Commercial TG from three different sources were purified by precipitation with isopropanol and evaluated in their physicochemical, rheological and structural aspects of galactomannans. For the structural evaluation and monosaccharide composition, Fourier Transform Infrared Spectroscopy (FT-IR) and Nuclear Magnetic Resonance (NMR) techniques were used. The physicochemical properties were calculated from the intrinsic viscosity determined by capillary viscosimetry and the rheological properties were determined by rotational viscometry. The stability of aqueous mixtures of TG with sodium caseinate (NaCas) and whey protein concentrate (WPC), as well the rheological behavior, was evaluated using the response surface methodology, considering NaCas, WPC and TG concentrations as factors. Response variables were zero shear viscosity (𝜂�0) and relaxation time (𝜆�). The intrinsic viscosity of TG was influenced by the combined effect of pH-temperature and the addition of salt. In diluted concentrations it showed shear thickening behavior and in semi-diluted and concentrated regimes it showed pseudoplastic with viscoelastic behavior, with the predominance of the viscous component at low frequencies. The TG and milk protein solutions presented metastable condition due to the increase in viscosity, varying the stabilization mechanisms for the TG-NaCas and TG-WPC solutions. The polymer mixtures showed pseudoplastic behavior, showing interaction between TG and the proteins studied, expressed by the increase of 𝜂�0 and 𝜆� in the highest gum concentration. Positive synergism was also found in the mixture of TG and XG, with a significant increase in the solid character of the gel and an increase in the strength of the formed gel.
Polysaccharides are used in the food industry due to their ability to modify rheological properties, stabilize emulsions or suspended particles or as a gelling agent, including Tara gum (TG) obtained from Tara seeds (Caesalpinia spinosa), which has limited used in the food industry, mainly due to restricted knowledge about their functional properties, and few research on the interactions with other polymers and compounds. The aim of this study is to gain understanding of Tara gum structure, rheological properties, molecular interactions in aqueous solution, in mixture with milk proteins and the formation of gels with Xanthan gum (XG), aiming at applications such as the development of new textures and new formulations for food beverage, cosmetic or pharmaceutical products. Commercial TG from three different sources were purified by precipitation with isopropanol and evaluated in their physicochemical, rheological and structural aspects of galactomannans. For the structural evaluation and monosaccharide composition, Fourier Transform Infrared Spectroscopy (FT-IR) and Nuclear Magnetic Resonance (NMR) techniques were used. The physicochemical properties were calculated from the intrinsic viscosity determined by capillary viscosimetry and the rheological properties were determined by rotational viscometry. The stability of aqueous mixtures of TG with sodium caseinate (NaCas) and whey protein concentrate (WPC), as well the rheological behavior, was evaluated using the response surface methodology, considering NaCas, WPC and TG concentrations as factors. Response variables were zero shear viscosity (𝜂�0) and relaxation time (𝜆�). The intrinsic viscosity of TG was influenced by the combined effect of pH-temperature and the addition of salt. In diluted concentrations it showed shear thickening behavior and in semi-diluted and concentrated regimes it showed pseudoplastic with viscoelastic behavior, with the predominance of the viscous component at low frequencies. The TG and milk protein solutions presented metastable condition due to the increase in viscosity, varying the stabilization mechanisms for the TG-NaCas and TG-WPC solutions. The polymer mixtures showed pseudoplastic behavior, showing interaction between TG and the proteins studied, expressed by the increase of 𝜂�0 and 𝜆� in the highest gum concentration. Positive synergism was also found in the mixture of TG and XG, with a significant increase in the solid character of the gel and an increase in the strength of the formed gel.
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Palavras-chave
Reologia, Géis, Proteínas do leite, Equilíbrio de fases, Galactomananas, Rheology, Gels, Milk proteins, Phase equilibrium, Galactomannans