Tesis doctoral de Irene Rodriguez Meizoso
In this phd report, we present the main results obtained from the green processes development to obtain food antioxidants from natural origin using subcritical water and other compressed fluids. this work deals with obtaining new functional ingredients, such as antioxidants, from plants and microalgae, using the most green solvent known, water, by subcritical water extraction (swe) (at high pressure and temperature). Moreover, by using another green solvent, supercritical co2, we have deepened in purifying a certain antioxidant by using supercritical fluids extraction as support technique. finally, we have taken advantage of the supercritical co2 properties in different particle formation processes as an efficient alternative to the traditional drying processes needed once samples are obtained. presentation and objectives this report is divided into eight chapters. Chapter i is an introduction about characteristics and applications of compressed fluids in food science and technology, definition of functional food and a brief description of the novel functional ingredients, the natural sources of functional ingredients used in this work, and the applications of the chemical and functional characterization techniques used. in chapter ii the application of swe to obtain extracts with antioxidant activity to be used as a functional ingredient from the microalgae haematococcus pluvialis is described. The selectivity of the extraction according to the temperature and the influence of sample pretreatment in the extraction yield was studied. The functional (antioxidant activity analysis) and chemical characterization (hplcdad, hplc-qqqms and gc-ms) of the extracts was carried out. The presence of proved antioxidant compounds that could justify the extract bioactivity observed was studied. In this sense, intermediate caramelization products, maillard reaction products and the presence of simple phenols were studied. Swe allowed extraction yields around 30% in a fast and environmentally friendly way. The combined use of advanced techniques allowed the identification of vitamin e, simple phenolic compounds, caramelization products and possible maillard intermediate products as the responsible compounds of the antioxidant activity in the extracts obtained at high temperature (200 ºc). in chapter iii the application of swe to obtain extracts with antioxidant activity to be used as functional ingredients from the microalgae phormidium sp. Is described. Functional (antioxidant activity analysis) and chemical (tlc, hplcdad y hplc-qqqms) characterization was carried out. Citotoxicity of the extracts was also estudied to guarantee food safety. The use of pressurized fluids extraction has been proved to be suitable for the extraction of antioxidants from phormidium species. The use of tlc, hplc-dad and hplc-qaqms techniques allowed the correlation between the antioxidant activity and the carotenoids content in the case of the organic solvent extracts, and simple phenols in the case of the water extracts obtained at high temperatures. in chapter iv the application of swe to obtain extracts with antioxidant activity to be used as functional ingredients from oregano is described. Functional (antioxidant activity analysis and total phenol content) and chemical (hplcdad) characterization was carried out. Antioxidant activity of the extracts was correlated to the presence of flavones, flavanones and flavonols. Swe was proved to be selective for different compounds depending on the temperature. thus, the process could be scaled-up due to the good possibilities observed. next chapters (v,vi and vii) are within the framework of the national plan project (agl2004-06893-co2-o1/ali), entitled ¿study of the health benetif of rosemary antioxidants by in vivo assays and clinical trials with diabetic type i children. purification of carnosic acid by sfc with selective polymers¿, which has been carried out in different laboratories settled in department of food characterization of the institute of industrial fermentations (csic), biomaterials group of the institute of polymer science and technology (csic), department section of food science of the autonoma university of Madrid (uam), department of analytical chemistry of the san pablo-ceu university and the pediatrics-endocrinolgy service of la paz children¿s hospital. in chapter v, swe application to obtain extracts with antioxidant activity is described. The selectivity of swe with temperature to extract antioxidants from rosemary leaves, that could be used as functional ingredients, was studied. A chemical characterization of the extracts was carried out, and the extraction process was evaluated according to three parameters: extraction yield, antioxidant activity of the extracts, and carnosic acid (a potent antioxidant) content in comparison with the rest of compounds present in the extracts. optimization of the extraction with the commercial swe extractor was statistically achieved. The compound composition extracts is comparable to sequential extractions reported in bibliography, but better antioxidant activity was achieved. chapters vi and vii deal with the use of sfe and swe, coupled to the use of selective polymers, to purify carnosic acid present in rosemary (rosmarinus officinalis l.). As a previous step, chapter vi deals with the study of selective interactions between a polymer synthesized in our laboratory (ethylpyrrolidine methacrylate¿methyl methacrylate copolymer) and carnosic acid in supercritical media. The characterization of the samples was carried out by spectroscopic and thermogravimetric techniques like nmr, ftir and tga. Polar interactions between the pyrrolidine amine groups of the copolymer and the carboxylic group of the antioxidant were observed, and were found to be maintained when treating the samples under supercritical conditions. These results show the promising applications of the copolymer as a selective sorbent for the purification of carnosic acid by sfe, that was approached in chapter vii, together with a similar purifying approach by swe. Although none of these experiments were totally successful, interactions between carnosic acid and the copolymer were suggested to be maintained when using water at high temperature and pressure. the selectivity of swe coupled to the use of the selective copolymer led to extracts with 75% carnosic acid content. in chapter viii, a new particle formation process, environmentally clean, is described. The process is based on the use of supercritical fluids to dry complex extracts from rosemary leaves extracted with subcritical water. The efficiency of the process was evaluated according to the antioxidant activity of the particles, their composition (by hplc-dad) and their morphology (by scanning electron microscopy). Rosemary and oregano leaves were studied. The subcritical water flow in the drying process was observed to affect the particle morphology, with maximum 140 ¿m length at the tested conditions. The composition of the particles was similar to the swe extracts obtained in previous chapters of this thesis. moreover, the antioxidant activity of the particles obtained was comparable to the extracts one. in conclusion, in this thesis we have approached the following objectives: ¿ development of new extraction methods to obtain natural antioxidants based on subcritical water (swe) and comparison with the pressurized liquid extraction (ple) with other solvents. ¿ development of new chemical characterization methods to study the compounds responsible of the antioxidant activity of the extracts. ¿ study of new extraction processes combining sfe or swe with smart polymers for the selective purification of potent antioxidants (carnosic acid). Study of the polymer-antioxidant interactions in supercritical media. english summary ¿ development of new swe plus particle formation on-line processes by technologies based on supercritical fluids, for complex antioxidant extracts drying.
Datos académicos de la tesis doctoral «Desarrollo de procesos medioambientales limpios para la obtención de antioxidantes alimentarios de origen natural: agua subcrítica y otros fluidos comprimidos.«
- Título de la tesis: Desarrollo de procesos medioambientales limpios para la obtención de antioxidantes alimentarios de origen natural: agua subcrítica y otros fluidos comprimidos.
- Autor: Irene Rodriguez Meizoso
- Universidad: Autónoma de Madrid
- Fecha de lectura de la tesis: 25/02/2009
Dirección y tribunal
- Director de la tesis
- Elena Ibañez Ezequiel
- Tribunal
- Presidente del tribunal: guillermo Reglero rada
- María del coral Barbas arribas (vocal)
- Antonio Segura carretero (vocal)
- marja-liisa Riekkola (vocal)