Guilherme de Figueiredo Furtado

Breaking oil-in-water emulsions stabilized by yeast

Several biotechnological processes can show an undesirable formation of emulsions making difficult phase separation and product recovery. The breakup of oil-in-water emulsions stabilized by yeast was studied using different physical and chemical methods. These emulsions were composed by deionized water, hexadecane and commercial yeast (Saccharomyces cerevisiae). The stability of the emulsions was evaluated varying the yeast concentration from 7.47 to 22.11% (w/w) and the phases obtained after gravity separation were evaluated on chemical composition, droplet size distribution, rheological behavior and optical microscopy. The cream phase showed kinetic stability attributed to mechanisms as electrostatic repulsion between the droplets, a possible Pickering-type stabilization and the viscoelastic properties of the concentrated emulsion. Oil recovery from cream phase was performed using gravity separation, centrifugation, heating and addition of demulsifier agents (alcohols and magnetic nanoparticles). Long centrifugation time and high centrifugal forces (2 h/150,000×g) were necessary to obtain a complete oil recovery. The heat treatment (60°C) was not enough to promote a satisfactory oil separation. Addition of alcohols followed by centrifugation enhanced oil recovery: butanol addition allowed almost complete phase separation of the emulsion while ethanol addition resulted in 84% of oil recovery. Implementation of this method, however, would require additional steps for solvent separation. Addition of charged magnetic nanoparticles was effective by interacting electrostatically with the interface, resulting in emulsion destabilization under a magnetic field. This method reached almost 96% of oil recovery and it was potentially advantageous since no additional steps might be necessary for further purifying the recovered oil.

Heteroaggregation of lipid droplets coated with sodium caseinate and lactoferrin

Formation and characterization of droplet heteroaggregates were investigated by mixing two emulsions previously stabilized by proteins oppositely charged. Emulsions were composed of 5vol.% of sunflower oil and 95vol.% of sodium caseinate or lactoferrin aqueous dispersions. They were produced using ultrasound with fixed power (300W) and sonication time (6min). Different volume ratios (0-100%) of sodium caseinate-stabilized emulsion (droplet diameter around 1.75μm) to lactoferrin-stabilized emulsion (droplet diameter around 1.55μm) were mixed under conditions that both proteins showed opposite charges (pH7). Influence of ionic strength (0-400mM NaCl) on the heteroaggregates stability was also evaluated. Creaming stability, zeta potential, microstructure, mean particle diameter and rheological properties of the heteroaggregates were measured. These properties depended on the volume ratio (0-100%) of sodium caseinate to lactoferrin-stabilized emulsion (C:L) and the ionic strength. In the absence of salt, different zeta potential values were obtained, rheological properties (viscosity and elastic moduli) were improved and the largest heteroaggregates were formed at higher content of lactoferrin-stabilized emulsion (60-80%). The system containing 40 and 60vol.% of sodium caseinate and lactoferrin stabilized emulsion, respectively, presented good stability against phase separation besides showing enhanced rheological and size properties due to extensive droplets aggregation. Phase separation was observed only in the absence of sodium caseinate, demonstrating the higher susceptibility of lactoferrin to NaCl. The heteroaggregates produced may be useful functional agents for texture modification and controlled release since different rheological properties and sizes can be achieved depending on protein concentrations.

β-Carotene-loaded nanostructured lipid carriers produced by solvent displacement method

Tristearin solid lipid nanoparticles and tristearin/high oleic sunflower oil nanostructured lipid carriers were produced by solvent displacement method. All conditions allowed forming polydisperse particles within nanometric range and the presence of high oleic sunflower oil did not affect the particles mean size. Nevertheless, incorporation of β-carotene reduced the particles polydispersity. Thermograms of solid lipid nanoparticles and nanostructured lipid carriers showed that sunflower oil generated a crystal order disturbance, since nanoparticles with less-organized lipid matrix were produced. Nanostructured lipid carriers exhibited an improvement of β-carotene loading capacity when compared with solid lipid nanoparticles, which enhanced with the increasing of high oleic sunflower oil content. Although total β-carotene degradation was similar for all systems, color analysis showed that the degradation of encapsulated β-carotene was lower for high sunflower oil content. Nanostructured lipid carriers exhibited advantages over the solid lipid nanoparticles, such as enhanced drug loading capacity and prevention of drug expulsion, which makes this a versatile delivery system for food applications.

High solids emulsions produced by ultrasound as a function of energy density

The use of emulsifying methods is frequently required before spray drying food ingredients, where using high concentration of solids increases the drying process yield. In this work, we used ultrasound to obtain kinetically stable palm oil-in-water emulsions with 30g solids/100g of emulsion. Sodium caseinate, maltodextrin and dried glucose syrup were used as stabilizing agents. Sonication time of 3, 7 and 11min were evaluated at power of 72, 105 and 148W (which represents 50%, 75% and 100% of power amplitude in relation to the nominal power of the equipment). Energy density required for each assay was calculated. Emulsions were characterized for droplets mean diameter and size distribution, optical microscopy, confocal microscopy, ζ-potential, creaming index (CI) and rheological behavior. Emulsions presented bimodal size distribution, with D[3,2] ranging from 0.7 to 1.4μm and CI between 5% and 12%, being these parameters inversely proportional to sonication time and power, but with a visual kinetically stabilization after the treatment at 148W at 7min sonication. D[3,2] showed to depend of energy density as a power function. Sonication presented as an effective method to be integrated to spray drying when emulsification is needed before the drying process.

High-throughput continuous production of liposomes using hydrodynamic flow-focusing microfluidic devices

The microfluidic hydrodynamic flow-focusing is a simple technique for nanoscale liposome formation that provides several advantages compared to the traditional manufacturing techniques. This work aimed to perform a systematic study of the liposome formation using planar microfluidic devices with different channel aspect-ratios, as an alternative to enhance the throughput of liposome synthesis. In general, liposomes with a low polydispersity and a precise control of the size were successfully produced from alteration of the flow rate ratio and channel aspect-ratio. The higher aspect-ratio enabled the most rapid generation of liposomes with similar diameter and significant lower polydispersity index than the obtained by other batch technique. Besides, β-carotene was successfully incorporated into liposomes with efficiency of approximately 60% and the incorporation ability was not specific to a choice of microfluidic device aspect-ratio. The results suggest that the use of microfluidic devices could be employed for liposome production with a possible advantage to minimize the degree of parallelization of processes. These results demonstrate the potential technical feasibility of microfluidic processes for future industrial applications.

Cold gel-like emulsions of lactoferrin subjected to ohmic heating

Ohmic heating is a technique that has gained increasing attention because of its capacity to produce uniform heating, and claimed electrical influence on the functional and technological properties of treated protein dispersions. The aim of this work was to evaluate the influence of ohmic heating on the properties of cold gel-like emulsions, comparing them with those obtained by conventional heating. The effect of ohmic and conventional heating on physical and structural properties of lactoferrin was also addressed. Ohmic heating treatment resulted in less pronounced aggregation of lactoferrin, when compared to conventional heating. An increase of particle size, turbidity, intrinsic and extrinsic fluorescence values and a decrease of dichroic signal after heat treatment indicated an increase of protein interactions. Emulsions produced from heat-treated lactoferrin showed gel-like behavior which was related to the emulsifying capacity of lactoferrin, combined with the emulsification method and the heat pre-treatment applied to the protein. Rheological and microstructural properties were intrinsically related to the heat treatment of the protein since ohmic heating produced gel-like emulsions with a less rigid structure. These emulsions could be interesting for food applications containing heat-sensitive ingredients.

DESSORÇÃO E CALOR ISOSTÉRICO DE AMÊNDOAS DE BARU

O presente trabalho teve como objetivo determinar as isotermas de dessorcao e o calor isosterico de amendoas de baru sob condicoes de temperatura e umidade relativa do ar variando de 20, 30, 40 e 50°C e 4,3 a 82,9% respectivamente. Foram ajustados cinco modelos matematicos aos dados experimentais com a finalidade de se obter os parâmetros desses modelos e escolher aquele que melhor representasse as isotermas e para o calculo do calor isosterico. A escolha do melhor ajuste deu-se em funcao do coeficiente de determinacao (R 2 ) e do desvio medio relativo (P). De acordo com os resultados o modelo de Halsey foi o que melhor se ajustou as isotermas de dessorcao, podendo ser empregado para o calculo da umidade de equilibrio higroscopico de amendoas de baru e o calor isosterico variou de 443,33 a 631,91 kJ.kg -1 .

INFLUÊNCIA DE PRÉ-TRATAMENTOS NA CINÉTICA DE SECAGEM DE BANANA DA VARIEDADE TERRA (Musa Sapientum, Linneo)

O presente trabalho foi conduzido com o objetivo de estudar a influencia de diferentes pre-tratamentos na cinetica de secagem de banana da variedade Terra ( Musa sapientum, Linneo ). Os frutos de banana foram submetidas a tres pre-tratamentos: primeiramente as frutas foram descascadas e fatiadas em espessuras de 2 e 4 mm, posteriormente branquedas e nao branqueadas e finalmente submetidas a uma desidratacao osmotica em dois niveis de concetracao(2 e 5% de NaCl). As secagens foram realizadas utilizando-se um secador descontinuo de bandejas em escala de bancada. As temperaturas do ar de secagem foram entre 60 e 80oC e a velocidade foi de aproximadamente 1 m.s -1 . A fim de avaliar e selecionar o modelo apropriado para a secagem, quatro diferentes modelos empiricos foram ajustados aos dados experimentais de umidade e comparados. Para analisar os efeitos dos pre-tratamentos na cinetica secagem de banana da variedade terra, utilizou-se um planejamento experimental fracionario 2 III 4-1 , com quatro fatores e dois niveis de variacao, para a constante de secagem (K). Com os resultados obtidos, pode-se concluir: que o modelo matematico de Midilli e Kucuk , foi o que melhor ajustou-se aos dados experimentais; a espessura das amostras e a temperatura de operacao do secador influenciaram significativamente (p=0,05) na constante de secagem, sendo a magnitude da mesma diretamente proporcional ao aumento da temperatura de operacao do secador e inversamente proporcional a espessura das amostras .

Oil in water emulsions stabilized by maillard conjugates of sodium caseinate-locust bean gum

Abstract Conjugates composed by sodium caseinate and locust bean gum (LBG) were produced through Maillard reaction in order to enhance their emulsifying properties. The reactions were performed (80 °C/76% relative humidity) at three protein/polysaccharide ratios (0.3, 0.6, 1.2), and the conjugates were added in emulsions at two pH values (3.5 and 7). The formation of protein-polysaccharide conjugates was confirmed by SDS-polyacrylamide gel electrophoresis and by FTIR spectra. At both pH values, the conjugates subjected to longer reaction times presented less emulsifying capability, probably due to insoluble compounds formation. Furthermore, the conjugates provided high stability in O/W emulsions at pH 7 due to the electrostatic repulsion of protein charged groups. However, even though the conjugates were not charged at pH 3.5, the stabilization process occurred at this condition probably due to the formation of a thicker interfacial layer, which provided an increase in steric repulsion between the droplets. Thus, the conjugates formed by sodium caseinate and locust bean gum can be characterized as a good emulsifying agent to be applied in different pH conditions. Graphical Abstract

Gelled Double-Layered Emulsions for Protection of Flaxseed Oil

Multilayer systems may present different functional properties according to the number of layers deposited, the type of biopolymers, the sequence of biopolymer layers, and the solution properties used during deposition. In this study, gelatin-stabilized emulsions were coated with alginate in order to produce double-layered emulsions. Concentrations of both primary emulsion and alginate in the outer layer were evaluated by a stability map. Results indicated the occurrence of depletion flocculation in emulsions with lower gelatin concentration due to excess of alginate. Stable emulsions were atomized in a calcium chloride solution for producing microgels, which resulted in semi-rounded monomodal particles. Emulsification process promoted a reduction in the content of the secondary oxidation products of flaxseed oil as compared to non-emulsified oil, while the gelation process was responsible for a considerable improvement on oxidative stability with significant reduction on both primary and secondary oxidation products during storage. These lipid-based microgels could be potentially used as delivery systems with improved oxidative stability.