AN ENGINEERING APPROACH TO DESIGN FOOD STRUCTURES FOR THE DELIVERY OF TARGETED FUNCTIONALITY: APPLICATION TO BIOACTIVES ENCAPSULATION
Creators: name: ROVERSI, TOMMASO
Publisher: name: Universit� degli Studi di Milano
Year: 2014

description: The food industry is constantly challenged to meet consumer demands for new food products that are safe, convenient, affordable, pleasurable and healthy. An understanding of fundamental structure and function relationships of food components is a key to stimulate and accelerate the development of innovative, complex and highly structured products and suitable production processes. The goal of the Thesis is the design of health supporting food functions with development of food structure/health benefits relationships based on fundamental soft material concepts. New capsules for bioactive controlled release to be used as ingredient for new formulated foods have been designed and developed. Food material science, engineering process and soft matter?s basic principles are here linked to deliver new real products that could improve health and well-being.
A first step of our research, described in chapter 1, was focused on the selection of the most appropriate shell material to be used in capsules manufacturing. A number of studies were performed regarding the gelation kinetics and the rheological properties of alginate, a natural biopolymer having unique properties that have enabled it to be used as a matrix for the entrapment and/or delivery of a variety of biological agents. The kinetics of alginate gelation has been investigated by means of photon correlation imaging (collaboration with POLIMI) and large deformation rheology. Our results showed that the alginate gelling kinetics displays a peculiar non-diffusive behavior, and the subsequent restructuring of the gel structure shares several features in common with the aging of colloidal gels, in particular for what concerns the occurrence of heterogeneous dynamics effects. A comparative analysis of the gel macroscopic mechanical properties at different aging stages further highlights distinctive effects arising from the non-permanent nature of the bonds.
In addition to the selection of an appropriate shell material, the challenges in developing commercially viable microcapsules rely on the selection of the most appropriate process to provide the desired morphology and stability. Thus a second step of our work, described in chapter 2 of the thesis, was focused on the realization of a batch coaxial encapsulation unit on lab scale for the production of alginate microbeads. A dual jet of liquid core and liquid shell material was pumped through concentric extrusion nozzles and droplets were formed by jet cutting technology. The shell of the bead was then hardened in a cross-linking solution. After process optimization, microcapsules containing a liquid core of bioactive with a narrow size distribution and mean diameter of 0.73�0.03 mm were produced.
As third step (see chapter 3), different types of microcapsules were produced and tested for engineered release of bioactive. Alginate microspheres containing a liquid core of cyanocobalamin, in presence or not of a double coating polymer, were tested for vitamin release under simulated intestinal peristaltic flow conditions of the lumen content. The small intestine model, designed and implemented at the University of Birmingham, mimics the peristaltic flow patterns by means of a pneumatic mechanism that reproduces the characteristic segmentation movements responsible for the flow and mixing. Diffusional experiment showed a good retention of the carried vitamin under simulated intestinal condition, and an overall mass transfer was calculated. Diffusivity seems to be directly related to the wall material solubility. Microbeads containing a modified luminescent Bifidobacterium longum were also efficiently used to protect bacteria?s vitality under simulated gastric condition.
While designing a functional ingredient, a prerequisite is that it could accomplish a specific function whilst being palatable enough to be eaten. The engineering of these properties is necessary and extremely challenging and clearly can be obtained at multiple length scales. Thus, the last research topic faced in this thesis and here reported in chapter 4 was aimed to increase knowledge on the influence of size-scale of the structures designed for bioactive release. In particular the investigation, developed in collaboration with the Food and Soft Material Group at ETH of Zurich, focused on exploring the potential of using a physical inspired (solvent shifting) production process of biopolymer-based nanoparticles. Specifically, we clearly demonstrated the possibility to produce nanospheres with a diameter as much as small as 20 nanometers without using any kind of mixing energy. Nanoparticles were studied by using advanced optical techniques, such as dynamic light scattering and depolarized dynamic light scattering, and finally used in preliminary experiments to increase the stability of a spontaneous food emulsion.
A main deliverable of this thesis is a contribution in increasing knowledge on the influence of structure and physical properties of food materials on the nutritional and health inducing properties, an essential step which is needed in the studies of bio-physical and gastro intestinal engineering aspects of nutrient absorption. An innovative approach has been followed that explores the relationship: material properties-processing-destructurization behavior in the gut, aimed to food properties generation, preservation and delivery. It relies on the concepts of multiscale structure dynamics and on biophysics-driven strategies for structure design.