Ce travail de thèse s’inscrit dans le contexte identifié de la nécessité de développer de nouveaux polymères plus respectueux de l’environnement. Nous sommes convaincus que l’essor de ces matériaux « verts » exige d’utiliser des additifs « verts » lors de la formulation. Dans le but d’élaborer des additifs respectueux de l’environnement capables d’assurer la stabilisation du polymère au regard du cycle de vie, et en attachant une attention particulière à la valorisation de la biomasse, trois approches ont été étudiées. La première est une voie innovante qui consiste à utiliser un mélange de polyphénols issus des sous-produits de l’industrie vinicole, et de l’industrie du thé. La seconde voie est la valorisation d’une molécule issue du sous-produit majeur de l’industrie du blé. La troisième est une voie d’innovation récente, qui propose l’utilisation de nanocomposites hydroxydes doubles lamellaires (HDL) fonctionnalisés avec des stabilisants biosourcés. L’évaluation de leurs propriétés stabilisantes, est réalisée au regard des processus de thermo- et photo-oxydation, dans les polyoléfines. Les résultats très prometteurs de ce projet mettent en évidence le fort potentiel des molécules et composites d’origine biosourcée à maintenir les propriétés des polymères en conditions d’usages. / This thesis work falls within the identified context of the need to develop new polymers that are more environmentally friendly. We are convinced that the development of these "green" materials requires the use of "green" additives during formulation. To develop environmentally friendly additives capable of stabilizing the polymer, with respect to the life cycle, and paying special attention to biomass valorization, three approaches have been studied. The first is an innovative way of using a mixture of polyphenols from winery by-products and tea industry. The second way is the valorisation of a molecule from the major by-product of the wheat industry. The third is a recent route of innovation, which proposes the use of layered double hydroxides nanocomposites (LDH) functionalized with bio based stabilizers. The evaluation of their stabilizing properties is carried out in polyolefins, against thermo- and photo-oxidation processes. The very promising results of the project highlight the strong potential of bio based molecules and composites to maintain polymers properties under conditions of use.

PhD (Food Science) / Department of Food Science and Technology / Finger millet (FM) [Eleusine coracana] is an underutilised cereal grain used as a food source in South Africa. Increased research interest in FM has span over the years owing to its unique nutritional and bioactive composition. Following the recent interest in natural curative substances over their synthetic counterparts in the treatment of food dependent diseases, FM has shown potential nutraceutical effects. Some important health effects like antidiabetic, antioxidative, anti-inflammatory and antimicrobial properties have been reported in recent trials with FM. In view of the increasing utilisation and application of FM in the region of Thulamela Municipality, Vhembe District of South Africa, two common indigenous FM varieties (brown and dark brown) were obtained and analysed for their physicochemical properties, levels of minerals, phytic acid, phenolic compounds and antioxidant activities. For this process, malted non-alcoholic beverages were produced and analysed for their physicochemical properties, levels of phenolic compounds, and total phenolics and antioxidant activities. FM grains were soaked, germinated and kilned at an interval of 24 h for 96 h, using sorghum as an external reference. Mineral composition of the FM and sorghum samples were analysed using an inductively coupled plasma atomic emission spectroscopy (ICP-AES) and mass spectroscopy (ICP-MS), and atomic absorption spectrometer (AAS). Identification and quantification of phenolic compounds were performed using ultra-performance liquid chromatography mass spectrometer (UPLC-MS). All experiments were performed in triplicate except for the UPLC-MS analysis of the malted non-alcoholic beverages that was done in duplicate. Data were analysed by one way analysis of variance, and the mean values were separated by Duncan’s multiple comparison test using SPSS version 24.0. Data showed that the FM varieties were rich in macro- and micro- or trace elements. The macro-elements calcium, magnesium, potassium, phosphorus and sulphur were found in high amounts ranging from 1597.37 mg/ kg – 6775.03 mg/ kg; iron, zinc, strontium and silicon were found in significant amounts in the range 21.47 mg/ kg – 55.67 iii mg/ kg, copper and boron were found in low amounts (2.2 mg/ kg – 7.7 mg/ kg), along with selenium and cobalt (0.02 mg/ kg – 0.05 mg/ kg). Heavy metals, barium and aluminium were found in the FM varieties. Varietal difference was found to play an important role in the mineral content of the grains during malting. Malting for 24 h reduced mineral content except for sodium. Beyond 48 h of malting, mineral content increased, particularly, for 96 h in FM grain malt. Significant (p < 0.05) increases in the mineral content of FM varieties were noted at 48 h and 96 h of malting. Increase occurred at 72 h of malting for potassium, iron and boron. Malting did not have any effect on the manganese content of the dark brown FM; however, it increased the manganese content at 48 h of malting for brown FM. Malting for 96 h significantly (p < 0.05) reduced sodium content. Consecutive decrease in phytic acid content of the grains was not recorded with durations in malting time. Although statistically significant differences (p < 0.05) were observed, malting did not result in too much change in the physicochemical properties of the grains. Several flavonoids, catechin, epicatechin, quercetin, taxifolin, and hesperitin were isolated, whilst protocatechuic acid was the only phenolic acid detected in the unmalted and malted FM. Increases in catechin, epicatechin and protocatechuic acid were observed for 72 and 96 h malt of brown FM with similar observations recorded for sorghum. Complete loss of taxifolin, catechin, and hesperitin were noted with malting time. FM grains exhibited 2, 2-diphenyl-1-picrylhydrazyl (DPPH), 2, 2՛-azinobis-3-ethylbenzthiazoline-6-sulfonic acid (ABTS) radical scavenging action and iron reducing activities. Increased iron reducing activity alongside ABTS radical scavenging activity was recorded with malting time. A fermentation-time dependent decrease in the pH of the non-alcoholic beverages, with a corresponding increase in sugar content were recorded. A similar decrease was also recorded for the viscosities of the beverages. The FM malt beverages were found to contain a higher amount of citric acid compared to the sorghum malt beverage. A decrease in the citric acid content with fermentation time was noted in the grain malt beverages fermented with Lactobacillus fermentum, particularly for the iv FM beverage. The phenolic compounds detected in the FM malt beverages fermented with the grain microbial flora and Lactobacillus fermentum were protocatechuic acid, catechin and epicatechin. Taxifolin and kaempferol along with the earlier mentioned compounds were detected in the sorghum malt beverage. Catechin was found in higher amount compared to other phenolic compounds in the FM and sorghum malt beverages. FM malt beverages were found to contain a higher amount of total phenolics compared to the beverage prepared from sorghum malt. Fermentation with the grains’ microbial flora and L. fermentum resulted in reduced total phenolics of FM and sorghum malt beverages, particularly after 24 h of fermentation. A fermentation-time dependent decrease in total phenolics of FM beverages fermented with L. fermentum was noted. Fermentation within 24 - 48 h using the grain microbial flora showed higher total individual phenolic compounds for the dark brown FM and sorghum, compared to other fermentation periods. Fermentation of the beverages for 24 h retained a higher amount of the total phenolics compared to other fermentation periods, especially for the L. fermentum beverages. Reduced total phenolic content and antioxidant activity of the beverages were noted at 24 h of fermentation for the two microbial sources. Significant (p < 0.05) increases in total phenolics were observed within 72 – 96 h of fermentation of the brown FM malt beverage with the grains’ microbial flora. Fermentation for 72 h and 96 h with L. fermentum increased the total phenolic content of the brown FM. Increase in total flavonoid content (TFC) of brown FM malt beverage was noted at 72 h fermentation for both microbial sources. Unlike with L. fermentum, no significant (p > 0.05) change in TFC was observed for the dark brown FM beverage after 24 h fermentation with the grains’ microbial flora. Beverages exhibited DPPH, ABTS radical scavenging action and iron reducing activities, which were significantly (p < 0.05) reduced at 96 h fermentation for both microbial sources. The 24 h fermented beverage retained a higher amount of total phenolic and flavonoid contents, and had higher antioxidant activity compared to other fermentation periods for both microbial sources. The study shows that FM is a rich source of essential minerals and v phenolic compounds, and demonstrates that 72 to 96 h of malting has a positive effect on minerals and certain phenolic compounds over the 48 h malting period widely used for preparation of FM malt. The presence of hesperitin in FM grain was established. A new method was developed for the production of FM non-alcoholic beverage with measurable amounts of health-promoting compounds. An ideal fermentation period (24 h) for FM malt non-alcoholic beverage production with enhanced health-promoting compounds, using Lactobacillus fermentum was demonstrated. Fermentation limit (96 h) for production of FM malt beverage using either the grain microbial flora or L. fermentum was confirmed. These findings provide a rationale for increased utilisation of FM as a functional food grain, and its use as malt in production of non-alcoholic beverage for health promotion and wellness. / NRF

Tesis por compendio / [ES] La población mundial está en constante crecimiento, por lo que la soberanía alimentaria se ha convertido en un desafío crucial. Se estima que la demanda de alimentos de origen animal aumentará en un 68% para el año 2050, lo cual resulta insostenible a nivel medioambiental. Así, impulsar un mayor consumo de proteína vegetal se plantea como una de las estrategias dirigidas a promover la sostenibilidad ambiental, asegurando la disponibilidad de proteína dietética para toda la población. Si bien ciertas las legumbres y pseudocereales son una excelente fuente de nutrientes y en particular de proteína, también contienen ciertos antinutrientes que pueden limitar su digestibilidad. Este aspecto es especialmente relevante en aquellos grupos poblaciones con alteraciones gastrointestinales, como las que pueden aparecer con la edad en población sénior. En este contexto, el objetivo general de esta tesis doctoral es aplicar la fermentación en estado sólido (FES) como bioestrategia para la obtención de harinas de lenteja y quinoa con digestibilidad y bioaccesibilidad mejoradas. Para alcanzar este objetivo, se llevó a cabo la fermentación con el hongo Pleurotus ostreatus, en dos variedades de lentejas y quinoa, y se estabilizaron posteriormente mediante secado por aire caliente a diferentes temperaturas, además de la liofilización como método de referencia. Posteriormente, las harinas fermentadas fueron digeridas in vitro simulando el proceso digestivo de un adulto sano (estándar de referencia), así como en condiciones alteradas del adulto mayor. Los resultados obtenidos evidenciaron un incremento de proteína total, así como de la actividad inhibidora de la enzima convertidora de angiotensina (ECA), conjuntamente con una disminución del contenido en ácido fítico, todo ello como resultado de la actividad metabólica del hongo sobre el sustrato. A pesar de que la FES también ocasionó una reducción de la actividad antioxidante, el posterior secado por aire caliente, especialmente a 70 °C incrementó este parámetro. Asimismo, la FES y el secado por aire caliente promovieron cambios en el perfil fenólico, disminuyendo algunos compuestos e incrementando otros como el ácido gálico hasta 5 veces su contenido inicial. En cuanto al perfil volátil de las harinas fermentadas, este se caracterizó por un aroma dulce, afrutado y con matices a cacao, acompañado de notas de setas y sustratos cocidos, debido a las concentraciones de benzaldehído, hexanal, nonanal, furfural y 1-octen-3-ol que se generaron durante la fermentación. Por otro lado, con respecto a la digestibilidad de las harinas fermentadas en condiciones estándar de adulto sano, la FES y el secado a 70 °C incrementó la hidrólisis de las proteínas, así como la liberación de aminoácidos hidrófobos y aminoácidos cargados negativamente. La FES también disminuyó la actividad inhibidora de la ECA en los digeridos, sin embargo, ésta aumentó después del secado a 70 °C debido a las melanoidinas generadas durante el secado. Además, las propiedades antioxidantes y la bioaccesibilidad de minerales también se vieron incrementados con la FES y el posterior secado a 70 °C. Finalmente, la simulación de las alteraciones gastrointestinales que comúnmente se dan en el adulto mayor, indicaron que estas impactaban negativamente en la mayoría de los parámetros evaluados, a excepción de la bioaccesibilidad del magnesio, hierro y calcio en comparación con el modelo estándar. En conclusión, se ha logrado mejorar el perfil nutricional y funcional de las nuevas harinas obtenidas por fermentación con el hongo P. ostreatus, y posterior secado por aire caliente en comparación con las harinas obtenidas a partir de sustrato no fermentado, conduciendo esto a una mejora significativa en la digestibilidad y la bioaccesibilidad de los nutrientes, lo que puede ser especialmente relevante para el diseño de alimentos orientados a grupos de población con alta demanda de proteína de fácil digestión. / [CA] La població mundial està en constant creixement, per la qual cosa la sobirania alimentària ha esdevingut un desafiament crucial. S'estima que la demanda d'aliments d'origen animal augmentarà un 68% per a l'any 2050, cosa que resulta insostenible a nivell mediambiental. Així, impulsar un consum més gran de proteïna vegetal es planteja com una de les estratègies dirigides a promoure la sostenibilitat ambiental, assegurant la disponibilitat de proteïna dietètica per a tota la població. Si bé certs els llegums i pseudocereals són una excel·lent font de nutrients i en particular de proteïna, també contenen certs antinutrients que poden limitar-ne la digestibilitat. Aquest aspecte és especialment rellevant en aquells grups de poblacions amb alteracions gastrointestinals, com les que poden aparèixer amb l'edat en població sènior. En aquest context, l'objectiu general d'aquesta tesi doctoral és aplicar la fermentació en estat sòlid (FES) com a bioestratègia per obtenir farines de llentia i quinoa amb digestibilitat i bioaccessibilitat millorades. Per assolir aquest objectiu, es va dur a terme la fermentació amb el fong Pleurotus ostreatus, en dues varietats de llenties i quinoa, i es van estabilitzar posteriorment mitjançant assecat per aire calent a diferents temperatures, a més de la liofilització com a mètode de referència. Posteriorment, les farines fermentades van ser digerides in vitro simulant el procés digestiu d'un adult sa (estàndard de referència), així com en condicions alterades de l'adult més gran. Els resultats obtinguts van evidenciar un increment de proteïna total, així com de l'activitat inhibidora de l'enzim convertidor d'angiotensina (ECA), conjuntament amb una disminució del contingut en àcid fític, com a resultat de l'activitat metabòlica del fong sobre el substrat. Tot i que la FES també va ocasionar una reducció de l'activitat antioxidant, el posterior assecat per aire calent, especialment a 70 °C va incrementar aquest paràmetre. Així mateix, la FES i l'assecatge per aire calent van promoure canvis en el perfil fenòlic, disminuint alguns compostos i incrementant-ne d'altres com l'àcid gàlic fins a 5 vegades el contingut inicial. Quant al perfil volàtil de les farines fermentades, aquest es va caracteritzar per una aroma dolça, afruitada i amb matisos a cacau, acompanyat de notes de bolets i substrats cuits, a causa de les concentracions de benzaldehid, hexanal, nonanal, furfural i 1-octen -3-ol que es van generar durant la fermentació. D'altra banda, pel que fa a la digestibilitat de les farines fermentades en condicions estàndard d'adult sa, la FES i l'assecatge a 70 °C va incrementar la hidròlisi de les proteïnes, així com l'alliberament d'aminoàcids hidròfobs i aminoàcids carregats negativament. La FES també va disminuir l'activitat inhibidora de l'ACA en els digerits, però aquesta va augmentar després de l'assecat a 70 °C a causa de les melanoïdines generades durant l'assecat. A més, les propietats antioxidants i la bioaccessibilitat de minerals també es van veure incrementats amb la FES i el posterior assecat a 70 °C. Finalment, la simulació de les alteracions gastrointestinals que comunament es donen a l'adult major, van indicar que aquestes impactaven negativament a la majoria dels paràmetres avaluats, a excepció de la bioaccessibilitat del magnesi, ferro i calci en comparació del model estàndard. En conclusió, s'ha aconseguit millorar el perfil nutricional i funcional de les noves farines obtingudes per fermentació amb el fong P. ostreatus, i posterior assecat per aire calent en comparació amb les farines obtingudes a partir de substrat no fermentat, conduint-ho a una millora significativa en la digestibilitat i la bioaccessibilitat dels nutrients, cosa que pot ser especialment rellevant per al disseny d'aliments orientats a grups de població amb alta demanda de proteïna de fàcil digestió. / [EN] The world's population is constantly growing, making food sovereignty a crucial challenge. It is estimated that the demand for animal-based food will increase by 68% by 2050, which is environmentally unsustainable. Thus, encouraging greater consumption of plant protein is one of the strategies aimed to promote environmental sustainability by ensuring the availability of dietary protein for the entire population. Although certain legumes and pseudocereals are an excellent source of nutrients and in particular protein, they also contain certain anti-nutrients that can limit their digestibility. This aspect is especially relevant in those population groups with gastrointestinal disorders, such as those that may appear with age in the elderly population. In this context, the general objective of this doctoral thesis is to apply solid-state fermentation (SSF) as a biostrategy to obtain lentil and quinoa flours with improved digestibility and bioaccessibility. To achieve this objective, fermentation with the fungus Pleurotus ostreatus was carried out on two varieties of lentils and quinoa, and subsequently stabilised by hot air drying at different temperatures, in addition by freeze-drying as a reference method. Subsequently, the fermented flours were digested in vitro simulating the digestive process of a healthy adult (reference standard), as well as under altered conditions of the elderly. The results obtained evidenced an increase in total protein, as well as in angiotensin-converting enzyme (ACE) inhibitory activity, together with a decrease in phytic acid content, all as a result of the metabolic activity of the fungus on the substrate. Although SSF also caused a reduction in antioxidant activity, subsequent hot air drying, especially at 70 °C, increased this parameter. Similarly, SSF and hot air-drying promoted changes in the phenolic profile, decreasing some compounds and increasing others such as gallic acid up to 5 times its initial content. The volatile profile of the fermented flours was characterised by a sweet, fruity aroma with hints of cocoa, accompanied by notes of mushrooms and cooked substrates, due to the concentrations of benzaldehyde, hexanal, nonanal, furfural and 1-octen-3-ol that were generated during fermentation. On the other hand, regarding the digestibility of the fermented flours under standard healthy adult conditions, SSF and drying at 70 °C increased the hydrolysis of proteins, as well as the release of hydrophobic and negatively charged amino acids. SSF also decreased the ACE inhibitory activity of the digests, however, it increased after drying at 70 °C due to melanoidins generated during drying. Furthermore, antioxidant properties and mineral bioaccessibility were also increased with SSF and subsequent drying at 70 °C. Finally, simulation of gastrointestinal disturbances commonly found in the older adult indicated that these impacted negatively on most of the parameters evaluated, with the exception of the bioaccessibility of magnesium, iron and calcium compared to the standard model. In conclusion, the nutritional and functional profile of the new flours obtained by fermentation with the fungus P. ostreatus, and subsequent hot air drying has been improved compared to flours obtained from unfermented substrate, leading to a significant improvement in the digestibility and bioaccessibility of nutrients, which may be particularly relevant for the design of foods oriented to population groups with a high demand of easily digestible protein. / Sánchez García, J. (2023). Desarrollo y caracterización de nuevas harinas de lenteja y quinoa fermentadas con Pleurotus ostreatus [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/202014 / Compendio