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Oxydation (des lipides ?) dans les matières grasses et les aliments : mécanismes et évaluation
No full textConception d’une préparation pour nourrisson native par filtration et conséquences sur sa digestion
No full textIntroduction
Les nourrissons français reçoivent en majorité des préparations pour nourrissons (PPN), qui reçoivent de nombreux traitements thermiques pour assurer leur sécurité sanitaire. Ces traitements peuvent dénaturer/agréger les protéines et favoriser la réaction de Maillard, ce qui peut impacter les propriétés nutritionnelles et organoleptiques des PPN. Le but de cette étude était de développer un itinéraire technologique permettant de produire une PPN conservant ses protéines à l’état natif tout en garantissant sa qualité bactériologique grâce à la filtration membranaire, et d’en évaluer l’impact sur la digestion des protéines.
Matériel et Méthodes
Des PPN en poudre ont été produites à l’échelle semi-industrielle à partir de lait frais écrémé et épuré, additionné d’un concentré de protéines solubles natives, tous deux obtenus par microfiltration (1,4 et 0,1 m, respectivement). Lactose, huiles végétales, minéraux et vitamines ont été ajoutés pour obtenir une PPN complète (1er âge) au sens de la réglementation. Trois modalités ont été testées : T-, sans traitement thermique ; T+, avec pasteurisation seule du concentré (75°C, 2min) avant séchage ; T+++, combinant pasteurisation du lait (72°C, 30s) et du concentré (85°C, 2 min).
Le taux de dénaturation protéique a été déterminé par Kjeldahl. Les produits de la réaction de Maillard ont été dosés par analyse de la furosine en chromatographie liquide en phase inverse et de la Nε-carboxyméthyl-lysine (CML) en spectrométrie de masse tandem (LC-MS/MS). Ces PPN ont été soumis à une digestion in vitro dynamique mimant le stade nouveau-né à terme. La cinétique de protéolyse a été évaluée par quantification des NH2 libérés et la microstructure des digestas a été suivie par granulométrie à diffraction laser et visualisée par microscopie confocale.
Résultats
Les PPN répondaient toutes aux exigences bactériologique et nutritionnelle, et présentaient des taux de dénaturation protéique différents (3 à 6% pour T- et T+ vs. 58% pour T+++). T+++ possédait une teneur en CML de 25% plus élevée que T- et T+, alors que des teneurs similaires en furosine étaient observées. Peu de différences ont été remarquées entre les PPN concernant le degré de protéolyse, ce qui peut masquer des différences d’hydrolyse des protéines individuelles. La microstructure des PPN était similaire avant digestion ; en revanche, les digestas provenant de T- et T+++ présentaient une microstructure différente en phase gastrique dès 80 min de digestion.
Conclusion
Cette étude a démontré la faisabilité de production de PPN conservant leurs protéines à l’état natif et sûres bactériologiquement. Les expérimentations de digestion in vitro ont montré que la microstructure des digestas était différente entre la PPN native et la PPN la plus traitée thermiquement, ce qui pourrait impacter les mécanismes de régulation de la digestion chez le nourrisson. La digestion des protéines individuelles sera investiguée prochainement
Taking Advantage of Bacterial Adaptation in Order to Optimize Industrial Production of Dry Propionibacterium freudenreichii
No full textPropionibacterium freudenreichii is a beneficial bacterium, used both as a probiotic and as
a cheese starter. Large-scale production of P. freudenreichii is required to meet growing consumers’
demand. Production, drying and storagemust be optimized, in order to guarantee high P. freudenreichii
viability within powders. Compared to freeze-drying, spray drying constitutes the most productive
and e cient, yet the most stressful process, imposing severe oxidative and thermal constraints.
The aim of our study was to provide the tools in order to optimize the industrial production of
dry P. freudenreichii. Bacterial adaptation is a well-known protective mechanism and may be used
to improve bacterial tolerance towards technological stresses. However, the choice of bacterial
adaptation type must consider industrial constraints. In this study, we combined (i) modulation
of the growth medium composition, (ii) heat-adaptation, and (iii) osmoadaptation, in order to
increase P. freudenreichii tolerance towards technological stresses, including thermal and oxidative
constraints, using an experimental design. We further investigated optimal growth and adaptation
conditions, by monitoring intracellular compatible solutes accumulation. Glucose addition, coupled
to heat-adaptation, triggered accumulation of trehalose and of glycine betaine, which further provided
high tolerance towards spray drying and storage. This work opens new perspectives for high quality
and fast production of live propionibacteria at the industrial scale
Critical issues on magnesium status and magnesium assessment, from cell to clinic
No full textThis speech will introduce a roundtable on the assessment of magnesium status, focusing on current
knowledge and future trends. Suboptimal magnesium intake in a large part of the population in western countries
supports an increased risk of latent magnesium deficiency. This mild and chronic deficiency is linked to a wide
spectrum of health disorders that can be considered nonspecific and can lead to progressive and severe health
deterioration, especially cardiometabolic diseases. In turn, several pathophysiological conditions e.g. metabolic
syndrome, obesity, type 2 diabetes, stress and dysfunctions related to aging can contribute and aggravate chronic magnesium deficiency. The diagnosis of latent deficiency is difficult because of nonspecific clinical symptoms and magnesemia often within reference intervals. Current clinical laboratory tests are almost limited to total serum magnesium. Less frequently ionized serum magnesium, red blood cell magnesium and urinary excretion of magnesium are measured. However, the assessment of magnesium status to diagnose latent deficiency remains problematic because only subtle changes occur in these parameters and there is a large inter-individual variability. Magnesium is primarily an intracellular cation and is found mainly in bone and soft tissues. Therefore, it is difficult to develop a rapid and robust test representative of intracellular magnesium or body magnesium in humans. The purpose of the presentation and the roundtable is to discuss progress in various areas (chemistry, molecular biology, mass spectrometry), offering great opportunities for the development of new methods for evaluating magnesium status, e.g. use of stable isotopes of magnesium, new dyes for intracellular magnesium or magnesium metabolism related gene expression measurements. In addition, it can be considered that magnesium deficiency diagnosis and deficiency risk patterns can be obtained from combined data composed of questionnaires, laboratory tests and physiological measurements
Une intervention au domicile mobilisant différentes dimensions du plaisir alimentaire permet-elle de réduire la charge calorique des goûters consommés par des enfants ?
No full textFluvio-lacustrine sedimentation in the agadir-tissint feija (Anti-atlas, morocco): A promising palaeoclimate archive for the last glacial cycle in northwest africa
No full textMountainous depocentres are often the single available archives in intracontinental areas. As such, the investigation of their sedimentary dynamics is the only way to reconstruct palaeoenvironmental evolution in these peculiar regions. Here, the basin-scale sedimentary dynamics of the Agadir-Tissint Feija (i.e. feija is the local name for lowlands) are discussed together with new palaeoenvironmental information on the late Quaternary in the north-western Sahara margin. The succession consists of up to ca 40 m thick fluvio-lacustrine deposits subdivided into three depositional sequences (S1-S3) that were deposited between ca 75 ka and ca 10 ka. S1 and S2 reflect the evolution of a palaeolake intercalated by carbonate-rich palustrine to alluvial plain environments, while S3 shows the transition to an entirely clastic alluvial plain environment. The three sequences are genetically associated with three pulses of tufa buildups at the outlet of the depocentre. Each pulse of tufa buildup is attributed to wet conditions, while each interruption is associated with drier conditions. The wet-dry alternation at the origin of S1 fits with summer insolation fluctuation suggesting that precession parameters may have paced long-term climate variability in the area. Superimposed on wet-dry cycles, submillennial-scale (750-900 year) shorter-term lake fluctuations are identified in S1 and S2; their origins may be related to North Atlantic Oscillation mechanisms. Furthermore, the sudden increase in clastic sediment supply in S3 evidences a change in sediment production in the catchment area attributed to lower temperatures established during the last glacial period. Finally, this newly identified continental archive is unique at the northern Sahara margin; it enables reconstructions of the local and regional hydrological conditions during the last glacial cycle. Even if a more systematic investigation of palaeoclimate forcing is still necessary, the Agadir-Tissint Feija will potentially bring important information to understand past and anticipate future regional climate change
rst1 and ripr connect the cytosolic rna exosome to the ski complex in arabidopsis
No full textThe RNA exosome is a key 3'-5' exoribonuclease with an evolutionarily conserved structure and function. Its cytosolic functions require the co-factors SK17 and the Ski complex. Here we demonstrate by co-purification experiments that the ARM-repeat protein RESURRECTION1 (RST1) and RST1 INTERACTING PROTEIN (RIPR) connect the cytosolic Arabidopsis RNA exosome to the Ski complex. rst1 and ripr mutants accumulate RNA quality control siRNAs (rqc-siRNAs) produced by the post-transcriptional gene silencing (PTGS) machinery when mRNA degradation is compromised. The small RNA populations observed in rstl and ripr mutants are also detected in mutants lacking the RRP45B/CER7 core exosome subunit. Thus, molecular and genetic evidence supports a physical and functional link between RST1, RIPR and the RNA exosome. Our data reveal the existence of additional cytosolic exosome co-factors besides the known Ski subunits. RST1 is not restricted to plants, as homologues with a similar domain architecture but unknown function exist in animals, including humans
