Modélisation de la viscosité de suspensions de particules molles végétales et observation directe des particules en milieu encombré

Les pure?es de pommes sont des suspensions concentre?es de particules non colloi?dales (180 ?m), non- sphe?riques et tre?s de?formables. Ces particules sont de?limite?es par une paroi cellulaire ve?ge?tale et remplies par la phase continue. Sous contrainte ou lorsque la concentration en particules augmente, elles se compriment, ce qui rend difficile la de?termination de leur fraction volumique re?elle et la compre?hension de leurs proprie?te?s rhe?ologiques. En ge?ne?ral, le comportement rhe?ologique des suspensions de particules ve?ge?tales est de?crit par trois domaines de concentration : un domaine dilue? dans lequel les particules interagissent peu (newtonien), un domaine interme?diaire marque? par l'apparition d'un re?seau entre les particules (comportement de fluide a? seuil, caracte?rise? par un module e?lastique a? faible de?formation qui augmente fortement avec la concentration en particules) et un domaine concentre? dans lequel les particules sont contraintes de se de?former pour s'adapter a? l'espace environnant et permettre l'e?coulement (le module e?lastique est de l'ordre de 103 Pa et la de?pendance a? la concentration en particules diminue). En combinant microscopie confocale et reconstruction 3D, nous avons de?veloppe?? un protocole pour de?terminer le volume de cellules dans des suspensions concentre?es de particules ve?ge?tales. Ce travail a permis de mettre en e?vidence que le volume des cellules diminue uniquement dans les suspensions fortement concentre?es. Par observation directe au sein de l'e?chantillon, nous apportons ainsi la preuve de la capacite?? des particules ve?ge?tales a? se comprimer et a? diminuer ainsi leur volume lorsque la concentration augmente. Dans ce travail, nous proposons e?galement un moyen d'acce?der a? la fraction volumique apparente des particules et un mode?le de?crivant la de?pendance de la viscosite? a? la concentration sur une large plage de concentrations. Le mode?le propose?, adapte? du mode?le de Mendoza (Mendoza 2013), s'ajuste avec pre?cision aux re?sultats expe?rimentaux obtenus sur des pure?es de pommes de distribution granulome?trique variable et sur des suspensions mode?les reconstitue?es dans plusieurs phases continues. Les parame?tres du mode?le refle?tent la rigidite? et l'asphe?ricite? des particules. Ce travail offre des perspectives inte?ressantes pour l'industrie des fruits et le?gumes transforme?s et a permis une avance?e vers la mode?lisation de ces syste?mes. Re?fe?rences : Day L., Xu M., Øiseth S.K., Hemar Y. & Lundin L. (2010). Control of Morphological and Rheological Properties of Carrot Cell Wall Particle Dispersions through Processing. Food and Bioprocess Technology, 3(6), 928?934. doi :10.1007/s11947-010-0346-0. Espinosa-Mun?oz L., Renard C., Symoneaux R., Biau N. & Cuvelier G. (2013). Structural parameters that determine the rheological properties of apple puree. Journal of Food Engineering, 119(3), 619?626. doi :10.1016/j.jfoodeng.2013.06.014. Mendoza C.I. (2013). Model for the Shear Viscosity of Suspensions of Star Polymers and Other Soft Particles. Macromolecular Chemistry and Physics, 214(5), 599?604. doi :10.1002/macp.201200551

Antiplasmodial volatile extracts from Cleistopholis patens Engler & Diels and Uvariastrum pierreanum Engl. (Engl. & Diels) (Annonaceae) growing in Cameroon

In a search for alternative treatment for malaria, plant-derived essential oils extracted from the stem barks and leaves of Cleistopholis patens and Uvariastrum pierreanum (Annonaceae) were evaluated in vitro for antiplasmodial activity against the W2 strain of Plasmodium falciparum. The oils were obtained from 500 g each of stem barks and leaves, respectively, by hydrodistillation, using a Clevenger-type apparatus with the following yields: 0.23% and 0.19% for C. patens and 0.1% and 0.3% for U. pierreanum (w/w relative to dried material weight). Analysis of 10% (v/v) oil in hexane by gas chromatography and mass spectrometry identified only terpenoids in the oils, with over 81% sesquiterpene hydrocarbons in C. patens extracts and U. pierreanum stem bark oil, while the leaf oil from the latter species was found to contain a majority of monoterpenes. For C. patens, the major components were α-copaene, δ-cadinene, and germacrene D for the stem bark oil and β-caryophyllene, germacrene D, and germacrene B for the leaf oil. The stem bark oil of U. pierreanum was found to contain mainly β-bisabolene and α-bisabolol, while α- and β-pinenes were more abundant in the leaf extract. Concentrations of oils obtained by diluting 1-mg/mL stock solutions were tested against P. falciparum in culture. The oils were active, with IC50 values of 9.19 and 15.19 μg/mL for the stem bark and leaf oils, respectively, of C. patens and 6.08 and 13.96 μg/mL, respectively, for those from U. pierreanum. These results indicate that essential oils may offer a promising alternative for the development of new antimalarials

COVID-19: Is There Evidence for the Use of Herbal Medicines as Adjuvant Symptomatic Therapy?

Background: Current recommendations for the self-management of SARS-Cov-2 disease (COVID-19) include self-isolation, rest, hydration, and the use of NSAID in case of high fever only. It is expected that many patients will add other symptomatic/adjuvant treatments, such as herbal medicines. Aims: To provide a benefits/risks assessment of selected herbal medicines traditionally indicated for “respiratory diseases” within the current frame of the COVID-19 pandemic as an adjuvant treatment. Method: The plant selection was primarily based on species listed by the WHO and EMA, but some other herbal remedies were considered due to their widespread use in respiratory conditions. Preclinical and clinical data on their efficacy and safety were collected from authoritative sources. The target population were adults with early and mild flu symptoms without underlying conditions. These were evaluated according to a modified PrOACT-URL method with paracetamol, ibuprofen, and codeine as reference drugs. The benefits/risks balance of the treatments was classified as positive, promising, negative, and unknown. Results: A total of 39 herbal medicines were identified as very likely to appeal to the COVID-19 patient. According to our method, the benefits/risks assessment of the herbal medicines was found to be positive in 5 cases (Althaea officinalis, Commiphora molmol, Glycyrrhiza glabra, Hedera helix, and Sambucus nigra), promising in 12 cases (Allium sativum, Andrographis paniculata, Echinacea angustifolia, Echinacea purpurea, Eucalyptus globulus essential oil, Justicia pectoralis, Magnolia officinalis, Mikania glomerata, Pelargonium sidoides, Pimpinella anisum, Salix sp, Zingiber officinale), and unknown for the rest. On the same grounds, only ibuprofen resulted promising, but we could not find compelling evidence to endorse the use of paracetamol and/or codeine. Conclusions: Our work suggests that several herbal medicines have safety margins superior to those of reference drugs and enough levels of evidence to start a clinical discussion about their potential use as adjuvants in the treatment of early/mild common flu in otherwise healthy adults within the context of COVID-19. While these herbal medicines will not cure or prevent the flu, they may both improve general patient well-being and offer them an opportunity to personalize the therapeutic approaches

Étude des processus de structuration de la matière sous contraintes physico-chimiques et mécaniques

Publis013-iate-01

Effect of lignin removal on the properties of coconut coir fiber/wheat gluten biocomposite

UMR IATE AXE 2; Contact: [email protected] effect of fiber lignin content on biocomposite properties was investigated. Coconut fiber was treated with 0.7% sodium chlorite to selectively decrease amounts of lignin. The fiber lignin content was then reduced from 42 to 21 wt.%. The composition and mechanical properties of the individual modified fibers were characterized. Gluten-based materials reinforced with modified fibers were prepared by compression molding. Then, the mechanical properties, water sensibility, matrix glass transition and infrared spectra of biocomposites prepared with fibers containing various amounts of lignin were evaluated. This study showed that the addition of coconut coir fiber significantly improved properties of wheat gluten biomaterials. In addition, the variation of lignin content in the fibers, in the investigated range, had no significant effect neither on matrix deplasticization nor fiber/matrix adhesion, suggesting that a partial lignin removal is not an efficient way to improve the properties of natural fiber/plasticized protein biocomposite

Etude du procédé d'élaboration de membranes poly (ether-imide) par inversion de phase induite par des vapeurs de non-solvant (relations entre paramètres du procédé, cinétiques de transfert et structuration du matériau)

MONTPELLIER-BU Sciences (341722106) / SudocSudocFranceF