Development of bio-based nanoemulsions to improve physical and chemical stability of omega-3 fatty acids

The 19th Gums & Stabilisers for the Food Industry Conference: Hydrocolloid MultifunctionalityNowadays there is a high interest of food industry to develop nutritional food products. This concept promoted the development of bio-based structures to encapsulate bioactive compounds and thus enhance their physical and chemical stability during storage until the consumption. In this field nanotechnology can offers several advantages, not only improving water solubility but also in the increase of bioavailability of lipophilic bioactive compounds. Omega-3 polyunsaturated fatty acids (ω-3 fatty acids) are known for their functional properties such as: improving cardiovascular health, decrease inflammation, increase cognitive function, and influence on neurological and visual development. However, ω-3 fatty acids are highly susceptible to oxidation, have an intense odour and present low water solubility, which makes its direct application in foods extremely difficult. In order to reduce these problems, the nanoencapsulation, through the use of nanoemulsions can be used. In this work, Lactoferrin (Lf), a protein derived from milk with a wide range of reported biological activities (e.g. antioxidant, antimicrobial and cancer prevention) was used as natural emulsifier for the development of oil-in-water nanoemulsions. Nanoemulsions were produced with a high-pressure homogenizer applied for 5 cycles at 20000 psi. Different Lf concentrations (0.2; 0.6; 1; 2; 3; 4 and 5% (w/w)) were tested. The nanoemulsions physical properties were evaluated in terms of size and ζ- potential measurements using dynamic light scattering (DLS) and by surface tension using the Ring method. The morphology of nanoemulsions were analysed by transmission electron microscopy (TEM). The physical and chemical stability of these nanoemulsions was assessed during 50 days, at storage temperatures of 4 ºC and 25 ºC, being the chemical stability of nanoemulsions was evaluated by antioxidant activity measurements using DPPH radical scavenging assay. Results showed that according to the Lf concentration used different properties were obtained. Nanoemulsions with Lf concentrations between 2 and 5% (w/w) presented sizes around 160 nm and a ζ-potential higher than +30 mV. For concentrations below 2 % (w/w), nanoemulsions presented sizes around 200 nm and a ζ- potential bellow +30 mV. It was noticed that higher Lf concentrations lead to smaller sizes and higher ζ-potential values. By increasing the Lf concentration was observed a decrease on superficial tension of nanoemulsions. TEM measurements showed that nanoemulsions particles have defined spherical shape. Results also showed that nanoemulsions with Lf concentration above 2 % (w/w) present better properties (smaller sizes and higher ζ-potential) so the storage stability of these nanoemulsions were assessed. Nanoemulsions stored at 4 ºC did not exhibit significant variations in size and ζ-potential values, while at 25 ºC the nanoemulsions suffered an size increase (around 35 nm compared to initial value) and a reduction in ζ-potential (around 20 mV compared to initial value) during storage. At these conditions, it was also observed that nanoemulaions with Lf concentrations of 2 and 3 % (w/w) present an instability (variations of size and ζ-potential) after 14 days of storage at 25 ºC, while for higher Lf concentrations (4 and 5 % (w/w)) the changes only start to be noticed latter (after 29 days of storage). Antioxidant activity did not demonstrate significant changes before and after storage at both temperatures (IC50 was around 14 mg/g of solution). This work provides important information that can be useful for the design of nanoemulsions aiming the encapsulation of lipophilic compounds for pharmaceutical and food applications.info:eu-repo/semantics/publishedVersio

Desenvolvimento de nanoemulsões baseadas em biopolímeros para melhorar a estabilidade física e química de ácidos gordos de ómega-3

Dissertação de mestrado em Bioquímica Aplicada (área de especialização em Biotecnologia)Nowadays there is a high interest by the food industry to develop nutritional food products. This concept promoted the development of bio-based structures to encapsulate bioactive compounds and thus enhance their physical and chemical stability from storage up until consumption. Omega-3 (ω-3) is known for its functional properties such as improving cardiovascular health, decrease inflammation, increase cognitive function. However, ω-3 fatty acids are highly susceptible to oxidation, have intense odour and low water solubility, which makes its direct application in foods extremely difficult. In order to reduce these problems, nanoencapsulation, through nanoemulsions can be used. With this in mind, lactoferrin (Lf), a protein derived from milk with a wide range of reported biological activities (e.g. antioxidant, antimicrobial, cancer prevention) was used as natural emulsifier for the development of oil-in-water nanoemulsions for ω-3 encapsulation. The nanoemulsions were characterized and assessed by physical and chemical stability during storage. Nanoemulsions were also dried by freeze-drying and nanospray-drying and further characterized. ω-3 nanoemulsions were successfully produced through high pressure homogenization, with results showing that the concentration of Lf influenced size and superficial charge of the nanoemulsions droplets obtained. Nanoemulsions revealed physical stability when stored at 4 ºC for 69 days, while presenting instability at room temperature. The antioxidant capacity of the nanoemulsions did not show significative alterations over storage while a significative increase in oxidation was registered. Only the nanoemulsions dried by nanopray-drying presented defined structures. The rehydration of the powders resulted from freeze-drying was possible while powders obtained by nanospray-drying were not able to be rehydrated. Overall the results suggest that ω-3 nanoemulsions with physical stability can be produced using Lf while chemical stability was not achieved. The Lf nanoemulsions can also be dried to obtain powders with defined submicron particles but its rehydration its limited. This work provides important information that can be useful for the design of nanoemulsions and dry capsules aiming the encapsulation of lipophilic compounds for pharmaceutical and food applications.Hoje em dia existe um grande interesse da industria alimentar no desenvolvimento de produtos alimentares com elevado valor nutricional. Este conceito tem promovido o desenvolvimento de estruturas de origem natural para encapsular compostos bio-ativos, permitindo melhorar a sua estabilidade química e física, desde o armazenamento até ao seu consumo. O ómega-3 (ω-3) apresenta importantes propriedades funcionais tais como a melhoria de saúde cardiovascular, diminuição de inflamação, aumento de funções cognitivas. No entanto, é extremamente suscetível a oxidação, tem um odor intenso e uma baixa solubilidade em água, o que faz com que a sua aplicação direta em alimentos seja extremamente difícil. A nanoencapsulação deste composto surge como uma alternativa para solucionar tais problemas. A Lactoferrina (Lf) uma proteína derivada do leite, com inúmeras propriedades biológicas (p.e. antioxidante, antimicrobiana, prevenção de cancro) foi usada como emulsionante natural na produção de nanoemulsões óleo-em-água para a encapsulação de ω-3, as quais foram posteriormente caracterizadas e avaliadas a nível da estabilidade física e química durante o armazenamento. Estas foram ainda submetidas a 2 diferentes processos de secagem (liofilização e nanaopray-drying). Produziram-se com sucesso nanoemulsões através de homogeneização de alta pressão, tendo-se verificado que a concentração de Lf influencia o seu tamanho e carga superficial. As nanoemulsões, revelaram estabilidade física quando armazenadas (69 dias) a 4 ºC, mas não quando armazenadas à temperatura ambiente. A capacidade antioxidante, quando armazenadas (4 ºC durante 35 dias), não apresentou alterações significativas, enquanto que os valores de oxidação aumentaram. Apenas as nanoemulsões submetidas ao processo de nanaopray-drying apresentaram uma estrutura resultante bem definida, e apenas as nanoemulsões submetidas ao processo de liofilização foram possíveis de ser rehidratadas. A presente tese permitiu verificar que nanoemulsões de ω-3, com estabilidade física, podem ser produzidas, usando Lf, no entanto não foi possível obter estabilidade química. A sua secagem permite a obtenção de estruturas definidas. Este trabalho permitiu obter informação relevante para o desenvolvimento de nanoemulsões que tenham como objetivo a encapsulação de compostos lipofílicos para aplicações alimentares e farmacêuticas