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| Author(s): |
Joice Aline Pires Vilela
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | Campinas, SP. |
| Institution: | Universidade Estadual de Campinas (UNICAMP). Faculdade de Engenharia de Alimentos |
| Defense date: | 2016-01-09 |
| Examining board members: |
Rosiane Lopes da Cunha;
Edvaldo Sabadini;
Paulo José do Amaral Sobral;
Pedro Esteves Duarte Augusto;
Samantha Cristina de Pinho
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| Advisor: | Rosiane Lopes da Cunha |
| Abstract | |
Emulsions stabilized by solid particles, called Pickering emulsions, could be used as an alternative emulsion type in comparison to classic emulsions stabilized by surfactants. These emulsions are characterized by a high stability to coalescence and reduced sensitivity to environmental changes. Acylated (HA) and deacylated (LA) gellan were the materials studied in this work for future use in emulsions stabilization. Significant differences were observed between the properties of HA and LA gellans, mainly on rheological behavior and zeta potential, which allowed understanding the emulsion stabilization mechanism performed by these polysaccharides. Dispersions containing low polysaccharide concentrations showed that the thickening capacity and the zeta potential values of HA gellan was much higher than LA gellan. Moreover, the LA gellan did not show emulsifying capacity in the studied conditions. Regarding emulsions containing HA gellan, low concentrations of polysaccharide (from 0.05% w/w) were able to stabilize emulsions containing 30% (w/w) of sunflower oil. The effect of ionic strength in the emulsions containing gellan HA was also determined. Emulsions properties were quite dependent of the polysaccharide/salt ratio and also of the type of salt used. The increased viscosity of the continuous phase, the electrostatic repulsion between the charged droplets and deposition of solid particles onto the interface (Pickering) were the suggested stabilization mechanisms, and the predominance of each mechanism was dependent on the composition and conditions used to prepare the emulsions. Regardless of the stabilization mechanism, it is important to highlight the low polysaccharide concentrations used, showing that HA gellan can be potentially used as a stabilizer/emulsifier ingredient. This carbohydrate is GRAS and therefore it is an interesting option in the stabilization of food emulsions, especially considering the current interest in reducing the use of synthetic ingredients or animal derivatives, as egg or milk derivatives commonly used as emulsifiers. Another part of this work (Annex I) involved the study of coffee grounds particles, a byproduct of the food industry rich in carbohydrates, which particles can be applied in several areas. It was observed that the coffee grounds is a material consisting of particles with average size in a wide range (37 ?m to 10 mm), with heterogeneous morphology, and negative zeta potential at the natural pH (5.0). No significant differences in composition were observed among the fractions separated by size using sieves. Chemical and physical methods have been used to achieve size reduction of the coffee grounds particles. The use of rotor-stator followed by separation by filtration allowed obtaining micro/nanoparticles. Because of the low yield in obtaining these particles, their application in the stabilization of emulsions was not performed in this work (AU) | |
| FAPESP's process: | 12/11794-5 - Study and preparation of polysaccharide nanoparticles to stabilize Pickering emulsions |
| Grantee: | Joice Aline Pires Vilela |
| Support Opportunities: | Scholarships in Brazil - Doctorate |