Preparo e caracterização de emulsões e microcápsulas de óleo de buriti (Mauritia flexuosa) utilizando isolado proteico de soja e pectina de alta metoxilação como estabilizantes
Carregando...
Data
2018-03-23
Autores
Freitas, Mírian Luisa Faria
Título da Revista
ISSN da Revista
Título de Volume
Editor
Universidade Estadual Paulista (Unesp)
Resumo
A proposta desse trabalho foi a produção e caracterização de emulsões e microcápsulas de óleo de buriti utilizando isolado proteico de soja e pectina de alta metoxilação como estabilizantes. Os biopolímeros foram caracterizados, individualmente, por meio de análises de solubilização, carga, turbidimetria e microscopia ótica. O complexo isolado proteico de soja-pectina de alta metoxilação foi caracterizado por ensaios de turbidimetria e microscopia ótica. Para caracterizar o óleo de buriti realizaram-se determinações de propriedades físico-químicas e termofísicas, matéria insaponificável, composição em ácidos graxos, classes acilglicerólicas, composição triacilglicerólica, classes triacilglicerólicas e comportamento térmico. As emulsões de óleo de buriti foram caracterizadas por análises de estabilidade, tamanho das gotas, condutividade elétrica, intensidade de cargas, microscopia ótica, microscopia confocal de varredura a laser e microscopia eletrônica de varredura. O comportamento reológico das emulsões foi analisado através de ensaios em cisalhamento constante e cisalhamento oscilatório. Microcápsulas de óleo de buriti foram obtidas por meio da secagem por spray dryer da emulsão de óleo de buriti otimizada e adicionou-se maltodextrina como adjuvante de secagem. As microcápsulas, por sua vez, foram caracterizadas por meio das análises de cor, umidade, rendimento, tamanho de partículas, eficiência de encapsulação e retenção de carotenoides, eficiência de encapsulação e retenção de óleo, sorção de água, plastificação pela água e relaxação mecânica. A morfologia das microcápsulas foi observada por microscopia ótica e microscopia eletrônica de varredura. Através dos ensaios de caracterização dos biopolímeros, pôde-se notar que a pectina de alta metoxilação apresentou alta solubilização, independente do pH, e as cargas negativas aumentaram com o aumento do pH até estabilizarem. O isolado proteico de soja apresentou baixa solubilização perto do ponto isoelétrico, aumentando com o pH em soluções alcalinas, até chegar a 100% no pH 11. Esse biopolímero apresentou cargas positivas em pH abaixo do ponto isoelétrico e cargas negativas em pH acima do ponto isoelétrico. Em pH abaixo do ponto isoelétrico foi verificada a interação atrativa do isolado proteico de soja e pectina de alta metoxilação por meio da observação de complexos formados, definindo-se o pH de 3,5 para produção das emulsões. A caracterização do óleo de buriti atestou sua alta qualidade, revelando altos teores de carotenoides, tocoferóis e ácidos graxos monoinsaturados. O planejamento experimental DCCR levou à obtenção de uma emulsão em condições otimizadas rica em óleo, estável por pelo menos 7 dias, com tamanho de gotas reduzido, baixa condutividade elétrica e alto módulo de cargas negativas. Esse material foi caracterizado como pseudoplástico e apresentou comportamento viscoelástico com módulo de armazenamento maior que o módulo de dissipação. Por meio das análises microscópicas foi possível observar a interação do isolado proteico de soja com o óleo de buriti formando as gotículas e a interação da pectina de alta metoxilação com o isolado proteico de soja formando a dupla camada da emulsão. O excesso de pectina foi observado disperso na fase contínua, contribuindo para a estabilidade do sistema. As diferentes amostras de microcápsulas apresentaram diferença significativa (p ≤ 0,05) entre si com relação à cor, rendimento, eficiência de encapsulação e retenção de carotenoides e eficiência de encapsulação e retenção de óleo. A amostra contendo maior teor de maltodextrina apresentou coloração menos intensa, porém, maior rendimento, eficiência de encapsulação e retenção dos compostos bioativos. As temperaturas de transição vítrea e de relaxação das microcápsulas se mostraram dependentes da umidade relativa a que foram expostas, sendo que quanto maior a umidade relativa, menor a temperatura de transição vítrea e de relaxação.
The aim of this study was the preparation and characterization of buriti oil emulsions and microcapsules using soy protein isolate and high-methoxyl pectin as stabilizers. The biopolymers were characterized individually by analysis of solubilization, charge, turbidity and optical miscrocopy. The soy protein isolate-high-methoxyl pectin complexes were characterized by turbidity and optical microscopy analyses. Characterization of the buriti oil was performed by analyses of physicochemical and thermophysical properties, unsaponifiable matter, fatty acid composition, acylglycerol classes, triacylglycerol composition, triacylglycerol classes, and thermal behavior. The buriti oil emulsions were characterized by analyses of stability, particle size, electric conductivity, zeta potencial, optical microscopy, confocal laser scanning microscopy, and scanning electron microscopy. The rheological behavior of the emulsions was analyzed by constant shear and oscillatory shear tests. The buriti oil microcapsules were produced by spray drying of the optimized conditions for elaborating buriti oil emulsion added with maltodextrin as a drying aid. The microcapsules, in turn, were evaluated by analyses of colour, moisture content, encapsulation yield, particle size distribution, encapsulation efficiency and retention of carotenoids, encapsulation efficiency and retention of oil, water sorption, water plasticization and mechanical relaxation. The microcapsules morphology was analysed by optical and scanning electron microscopy. Through the biopolymer characterization, it could be noted that the highmethoxyl pectin showed high solubilization, independent of the pH, and the negative charges increased with increasing pH until stabilization. The soy protein isolate had low solubilization near the isoelectric point and it increased with increasing pH in alkaline solutions, up to reach 100% at pH 11. This biopolymer presented positive charges in pH below the isoelectric point and negative charges at pH above the isoelectric point. At pH lower than the isoelectric point there was attractive interaction between soy protein isolate and high-methoxyl pectin, leading to definition of the pH 3.5 for preparation of the emulsions. The characterization of buriti oil confirmed its high quality, showing high levels of carotenes, tocols and monounsaturated fatty acids. The CCRD experimental design was adequate for the study of buriti oil emulsions, leading to definition of an optimized conditions for producing emulsion rich in oil, stable for at least 7 days, with reduced droplet size, low electric conductivity and high modulus of negative charges. This material was characterized as pseudoplastic and showed viscoelastic behavior with storage modulus greater than the loss modulus. Moreover, through microscopic analysis it was possible to observe the interaction of soy protein isolate with buriti oil forming oil droplets and the interaction of high-methoxyl pectin with soy protein isolate forming the double layer of the emulsion. The excess pectin was observed dispersed in the continuous phase, contributing to system stability. The different samples of microcapsules presented significant differences (p ≤ 0.05) with respect to color parameters, encapsulation yield, encapsulation efficiency and retention of carotenoid, and encapsulation efficiency and retention of buriti oil. The sample with the highest maltodextrin content presented less intense coloration, in contrast, presented the highest encapsulation yield, encapsulation efficiency and retention of bioactive compounds. The glass transition and relaxation temperatures of the microcapsules were dependent on the ambient relative humidity, and the higher the relative humidity, the lower the glass transition temperature and the relaxation temperature.
The aim of this study was the preparation and characterization of buriti oil emulsions and microcapsules using soy protein isolate and high-methoxyl pectin as stabilizers. The biopolymers were characterized individually by analysis of solubilization, charge, turbidity and optical miscrocopy. The soy protein isolate-high-methoxyl pectin complexes were characterized by turbidity and optical microscopy analyses. Characterization of the buriti oil was performed by analyses of physicochemical and thermophysical properties, unsaponifiable matter, fatty acid composition, acylglycerol classes, triacylglycerol composition, triacylglycerol classes, and thermal behavior. The buriti oil emulsions were characterized by analyses of stability, particle size, electric conductivity, zeta potencial, optical microscopy, confocal laser scanning microscopy, and scanning electron microscopy. The rheological behavior of the emulsions was analyzed by constant shear and oscillatory shear tests. The buriti oil microcapsules were produced by spray drying of the optimized conditions for elaborating buriti oil emulsion added with maltodextrin as a drying aid. The microcapsules, in turn, were evaluated by analyses of colour, moisture content, encapsulation yield, particle size distribution, encapsulation efficiency and retention of carotenoids, encapsulation efficiency and retention of oil, water sorption, water plasticization and mechanical relaxation. The microcapsules morphology was analysed by optical and scanning electron microscopy. Through the biopolymer characterization, it could be noted that the highmethoxyl pectin showed high solubilization, independent of the pH, and the negative charges increased with increasing pH until stabilization. The soy protein isolate had low solubilization near the isoelectric point and it increased with increasing pH in alkaline solutions, up to reach 100% at pH 11. This biopolymer presented positive charges in pH below the isoelectric point and negative charges at pH above the isoelectric point. At pH lower than the isoelectric point there was attractive interaction between soy protein isolate and high-methoxyl pectin, leading to definition of the pH 3.5 for preparation of the emulsions. The characterization of buriti oil confirmed its high quality, showing high levels of carotenes, tocols and monounsaturated fatty acids. The CCRD experimental design was adequate for the study of buriti oil emulsions, leading to definition of an optimized conditions for producing emulsion rich in oil, stable for at least 7 days, with reduced droplet size, low electric conductivity and high modulus of negative charges. This material was characterized as pseudoplastic and showed viscoelastic behavior with storage modulus greater than the loss modulus. Moreover, through microscopic analysis it was possible to observe the interaction of soy protein isolate with buriti oil forming oil droplets and the interaction of high-methoxyl pectin with soy protein isolate forming the double layer of the emulsion. The excess pectin was observed dispersed in the continuous phase, contributing to system stability. The different samples of microcapsules presented significant differences (p ≤ 0.05) with respect to color parameters, encapsulation yield, encapsulation efficiency and retention of carotenoid, and encapsulation efficiency and retention of buriti oil. The sample with the highest maltodextrin content presented less intense coloration, in contrast, presented the highest encapsulation yield, encapsulation efficiency and retention of bioactive compounds. The glass transition and relaxation temperatures of the microcapsules were dependent on the ambient relative humidity, and the higher the relative humidity, the lower the glass transition temperature and the relaxation temperature.
Descrição
Palavras-chave
Carotenoides, Tocoferóis, Reologia, Morfologia, Spray drying, Retenção de compostos bioativos, Temperatura de transição vítrea, Temperatura de relaxação, Carotenoids, Tocopherols, Rheology, Morphology, Bioactive compounds retention, Glass transition temperature, Relaxation temperature