Secagem por atomização do suco de uva: microencapsulação das antocianinas
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Data
2016-02-25
Autores
Moser, Poliana [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
O suco de uva possui um alto teor de antocianinas, com elevada atividade antioxidante e grande potencial de uso como corante natural. Porém, a secagem dos sucos de frutas em spray dryer apresenta complicações devido à pegajosidade e elevada higroscopicidade dos pós, o que ocasiona problemas durante o processamento e armazenamento do produto. Uma alternativa para facilitar a secagem é a adição de carreadores, que também desempenham o papel de encapsulantes. O objetivo desse trabalho foi a obtenção do suco de uva em pó pelo processo de atomização, utilizando misturas de maltodextrina e proteínas de soja ou de soro de leite como agentes carreadores, visando proteger as antocianinas e obter um produto com boa estabilidade em relação às alterações físicas e químicas. Inicialmente, avaliou-se a influência das condições do processo sobre o rendimento, umidade, solubilidade e cor do suco em pó. As condições selecionadas para realizar a secagem do suco foram: temperatura de entrada do ar de 140 ºC, fluxo de ar de 500 L/h, vazão de alimentação de 2 mL/min e baixa concentração de carreador. Posteriormente, foram avaliados diferentes carreadores - misturas de proteína isolada de soja e maltodextrina (SM) e misturas de proteína concentrada de soro de leite e maltodextrina (WM) - no rendimento de processo, solubilidade, retenção de antocianinas, eficiência de encapsulação (EE), cor e morfologia das microesferas. As concentrações de agente carreador (CAC, g de carreador/g sólidos solúveis do suco) utilizadas foram na faixa de 0,65 a 1,35 para SM e de 0,15 a 0,85 para WM, enquanto as proporções de proteína foram de 5,86 a 34,14 g de proteína/100 g de agente carreador. Os sucos em pó apresentaram alta solubilidade e baixa umidade. Os pós produzidos com as misturas WM resultaram em alto rendimento e alta retenção de antocianinas, enquanto as misturas de SM apresentaram alta EE. Os tratamentos que apresentaram os melhores resultados globais foram: CAC = 1,25, 10% de proteína de soja; CAC = 1,00, 5.86% de proteína de soja; CAC = 0,75, 30% de proteína de soro; e CAC = 0,85, 20% de proteína de soro, sendo codificados como 1SM, 2SM, 1WM e 2WM, respectivamente. Os sucos atomizados com os carreadores selecionados foram avaliados quanto à distribuição de tamanho das partículas, pegajosidade, isotermas de sorção de água, temperatura de transição vítrea (Tg) e estabilidade das antocianinas expostas à luz. As isotermas de sorção foram classificadas como tipo II e o modelo de GAB foi o que melhor se ajustou aos dados experimentais. A temperatura de transição vítrea diminuiu com o aumento da atividade de água, confirmando o efeito plasticizante da água. No estudo da estabilidade frente à luz, verificou-se que o tratamento 1SM foi o que apresentou a melhor proteção das antocianinas. Finalmente, a estabilidade dos compostos fenólicos e a atividade antioxidante do suco de uva em pó armazenados nas temperaturas de 5 ºC, 25 ºC e 35 ºC durante 150 dias foi avaliada. As microesferas formuladas com 1SM, que possuía maior CAC, foram mais efetivas na proteção das antocianinas, enquanto o tratamento 1WM, que possuía menor CAC, não apresentou boa proteção. Com exceção do 1SM, os tratamentos aumentaram a sua proporção de antocianinas p-cumariladas com o tempo de armazenamento. Os flavonóis, os ácidos hidroxicinâmicos e os flavan-3-óis foram analisados no tempo inicial (0 dias) e no tempo final do armazenamento (150 dias). Após 150 dias, o tratamento 1SM apresentou perdas significativas de flavonóis. Todos os tratamentos tiveram perdas de ácidos hidroxicinâmicos, independente da temperatura de armazenamento, e perdas de flavan-3-óis a 35 ºC. Apesar das perdas de compostos fenólicos, o tempo e a temperatura não influenciaram a atividade antioxidante dos pós e a cor do suco de uva reconstituído, após 150 dias de armazenamento.
Grape juice has a high content of anthocyanins, with high antioxidant capacity and great potential to be used as a natural dye. Nevertheless, drying of fruit juices by atomization presents complications due to stickiness and high hygroscopicity of powders, which cause problems during processing and storage of the product. An alternative to facilitate drying is the addition of carriers that also play the role of encapsulants. The aim of this work was to produce grape juice powders by spray drying, using blends of maltodextrin and soy or whey protein as carrier agents, in order to protect the anthocyanins and to obtain a stable product with respect to physical and chemical changes. In a first step, the influence of process conditions on yield, moisture, solubility and color of powdered juice was evaluated. The conditions selected to perform drying of juice were: inlet-air temperature of 140 °C, air flow of 500 L/h, feed flow rate of 2 mL/min and low concentration of carrier. Subsequently, the use ofdifferent carriers - blends of soy protein isolate with maltodextrin (SM) and whey protein concentrated of milk with maltodextrin (WM) – was assessed on yield, solubility, anthocyanin retention, encapsulation efficiency (EE), color and morphology of the microspheres. The carrier agent concentration (CAC, g of carrier/g of soluble solids of the juice) used was in the range of 0.65 – 1.35 to SM, and of 0.15 – 0.85 to WM, whereas the protein ratio (R, g protein/100 g carrier agent) varied between 5.86 - 34.14. The grape juice powders presented high solubility and low water content. WM blends resulted in higher yields and higher anthocyanin retention than SM blends, whereas SM blends leaded to higher encapsulation efficiency. Treatments that presented the best overall results were: CAC = 1.25, 10 % soy protein; CAC = 1.00, 5.86 % soy protein; CAC = 0.75, 30 % whey protein; and CAC = 0.85, 20 % whey protein, which were coded as 1SM, 2SM, 1WM e 2WM, respectively. The powdered juices with the selected carrier formulations were evaluated for particle size distribution, water sorption isotherms, glass transition temperature (Tg), stickiness and light stability of anthocyanins. The sorption isotherms were classified as type II and the GAB model was well fitted to experimental data. The glass transition temperature decreased with the increase in water content, confirming the plasticizing effect of water. Regarding light stability, 1SM treatment showed the best anthocyanin protection. Finally, the stability of phenolic compounds and antioxidant activity of powdered grape juice - stored at 5, 25 and 35 ºC up to 150 days - were evaluated. The microspheres formulated with 1SM, which had the largest CAC, were more effective in the preservation of anthocyanins, whereas 1WM, which had the lowest CAC, did not provide good protection. With the exception of 1SM, the treatments increased the proportion of p-coumaroylated anthocyanins over storage time. Flavonols, hydroxycinnamic acid derivatives (HCAD) and flavan-3-ol were analyzed at initial (0 day) and final storage time (150 days). After 150 days, 1SM powder decreased flavonols. All treatments decreased HCAD, independently of the storage temperature, and lost flavan-3-ol at 35 ºC. Despite of all the aforementioned losses in the studied phenolic compounds, time and temperature did not influence on the antioxidant activity of the powder and reconstituted grape juice color, after 150 days of storage.
Grape juice has a high content of anthocyanins, with high antioxidant capacity and great potential to be used as a natural dye. Nevertheless, drying of fruit juices by atomization presents complications due to stickiness and high hygroscopicity of powders, which cause problems during processing and storage of the product. An alternative to facilitate drying is the addition of carriers that also play the role of encapsulants. The aim of this work was to produce grape juice powders by spray drying, using blends of maltodextrin and soy or whey protein as carrier agents, in order to protect the anthocyanins and to obtain a stable product with respect to physical and chemical changes. In a first step, the influence of process conditions on yield, moisture, solubility and color of powdered juice was evaluated. The conditions selected to perform drying of juice were: inlet-air temperature of 140 °C, air flow of 500 L/h, feed flow rate of 2 mL/min and low concentration of carrier. Subsequently, the use ofdifferent carriers - blends of soy protein isolate with maltodextrin (SM) and whey protein concentrated of milk with maltodextrin (WM) – was assessed on yield, solubility, anthocyanin retention, encapsulation efficiency (EE), color and morphology of the microspheres. The carrier agent concentration (CAC, g of carrier/g of soluble solids of the juice) used was in the range of 0.65 – 1.35 to SM, and of 0.15 – 0.85 to WM, whereas the protein ratio (R, g protein/100 g carrier agent) varied between 5.86 - 34.14. The grape juice powders presented high solubility and low water content. WM blends resulted in higher yields and higher anthocyanin retention than SM blends, whereas SM blends leaded to higher encapsulation efficiency. Treatments that presented the best overall results were: CAC = 1.25, 10 % soy protein; CAC = 1.00, 5.86 % soy protein; CAC = 0.75, 30 % whey protein; and CAC = 0.85, 20 % whey protein, which were coded as 1SM, 2SM, 1WM e 2WM, respectively. The powdered juices with the selected carrier formulations were evaluated for particle size distribution, water sorption isotherms, glass transition temperature (Tg), stickiness and light stability of anthocyanins. The sorption isotherms were classified as type II and the GAB model was well fitted to experimental data. The glass transition temperature decreased with the increase in water content, confirming the plasticizing effect of water. Regarding light stability, 1SM treatment showed the best anthocyanin protection. Finally, the stability of phenolic compounds and antioxidant activity of powdered grape juice - stored at 5, 25 and 35 ºC up to 150 days - were evaluated. The microspheres formulated with 1SM, which had the largest CAC, were more effective in the preservation of anthocyanins, whereas 1WM, which had the lowest CAC, did not provide good protection. With the exception of 1SM, the treatments increased the proportion of p-coumaroylated anthocyanins over storage time. Flavonols, hydroxycinnamic acid derivatives (HCAD) and flavan-3-ol were analyzed at initial (0 day) and final storage time (150 days). After 150 days, 1SM powder decreased flavonols. All treatments decreased HCAD, independently of the storage temperature, and lost flavan-3-ol at 35 ºC. Despite of all the aforementioned losses in the studied phenolic compounds, time and temperature did not influence on the antioxidant activity of the powder and reconstituted grape juice color, after 150 days of storage.
Descrição
Palavras-chave
Atomização, Proteínas, Maltodextrina, Compostos fenólicos, Estabilidade, Spray drying, Proteins, Maltodextrin, Phenolic compounds, Stability