Mariano Michelon

Designing Food Structure Using Microfluidics

Microfluidics is an emerging technology that can be employed as a powerful tool for designing structures in the food industry. Those structures can modify the texture and flavor perception in a food product or can be used as carrying vehicles for a wide range of bioactive compounds. Microfluidic processes occur in strictly laminar flow, which is quite interesting to process control. This results in particles with more homogeneous size and shape, which improve the properties of controlled release of active compounds and their stability. Innumerable complex structures can be designed, with single or multiple shells, one or more cores inside the particles. In addition, self-assembled structures can be formed in microfluidic devices. However, most of the published works have fundamental character. Fundamental studies are important to understand the physical phenomena that occur at the microscale, in order to obtain successful results in the design of microstructures. Especially in the case of food-grade ingredients, more complex variables have to be considered, such as their rheological and mass- and heat-transport properties. In this review, the fundamentals of microfluidics will be presented, such as the main forces and dimensionless numbers that are involved in the microscale processes and droplet formation regimes. In addition, the most common microfluidic devices will be described, covering their geometries and materials. The review will also present results from studies on structure design using microfluidics, including emulsion-based techniques for the production of microparticles and strategies for the production of self-assembled structures.

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-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.