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Methods assessment of self-tanning of a rapeseed meal fraction enriched in proteins and phenolic compounds
No full textConnectivité des gouttes de matières grasse par des agrégats de protéiques et texturation des émulsions.
No full textClassiquement, la texture des desserts lactés à pH neutre, est obtenue grâce à des épaississants ou des gélifiants. Dans certaines conditions, des agrégats de protéines laitières sont également capables de connecter les gouttelettes de l’émulsion et de texturer le système. Au cours de ces travaux, nous avons étudié la capacité de différents agrégats à texturer des émulsions tout en faisant le lien avec leurs propriétés d’adsorption et d’étalement à l’interface dans un mélange complexe contenant aussi des protéines solubles. L’objectif était de contrôler la compétition d’adsorption entre ces différentes espèces et au final, la composition interfaciale, afin de maîtriser la texture des émulsions. Les résultats montrent la possibilité de texturer les émulsions pendant l’homogénéisation (gel instantané) mais également au cours du stockage (gel différé), et ce, même pour des teneurs en matière grasse faible
Filtration de dispersions de micelles de caséine : propriétés physiques, rhéologiques et cohésives des couches accumulées à la surface de la membrane
No full textLors de l’ultra- ou de la microfiltration de lait écrémé, les micelles de caséine, particules colloïdales poreuses et déformables, viennent s’accumuler à la surface des membranes passant de l’état liquide (sol) à l’état solide (gel) sous certaines conditions. Cela conduit à des altérations notables des performances de la filtration. Afin de mieux maîtriser les opérations de filtration, il est nécessaire de mieux connaître les conditions opératoires qui conduisent à la formation de ces gels et leurs propriétés. Deux stratégies ont été adoptées pour cela : (i) une approche ex-situ, pour étudier les propriétés physiques, rhéologiques et cohésives des micelles de
caséine concentrées; (ii) une approche in-situ par diffusion de rayons X aux petits angles (SAXS) lors de l'ultrafiltration de micelles, afin de suivre les évolutions spatio-temporelles des profils de concentration en micelles de caséines à la surface de la membrane. Par l'approche ex-situ, il a été mis en évidence
des différences de comportement entre les dispersions de micelles de caséine à 7 et 20°C : à 7°C les micelles de caséine sont moins compressibles, leur concentration de transition sol-gel est plus basse et elles développent des interactions plus cohésives qu'à 20 °C. Par l'approche in-situ, les résultats montrent qu’il est possible d’éliminer partiellement les dépôts formés durant les filtrations tangentielles et frontales, en
relâchant la pression appliquée. L’élimination du dépôt semble se faire par gonflement du gel de micelles de caséine par diffusion du solvant à la fois du côté de la veine liquide (côté rétentat) et au voisinage de la membrane (côté perméat). Ceci permet d'envisager des perspectives en termes de rinçage et nettoyage des membranes.During skim milk ultra- or microfiltration, casein micelles that are porous and deformable colloidal particles, accumulate at the membrane surface and can turn from liquid state (sol) to solid state (gel) under some
operating conditions. This leads to significant alterations of the filtration performances. In order to control filtration operations, it is necessary to better understand the operating conditions that lead to the formation of these gels and to their properties. Two approaches have been developed to answer to this problematic: (i) an ex-situ approach, to study physical, rheological and cohesive prop erties of concentrated dispersions of casein micelles; (ii) an in-situ approach with Small-Angle X-ray Scattering (SAXS) to follow spatio-temporal
evolution of casein micelle concentration profiles at the membrane surface during casein micelle
ultrafiltration. By the ex-situ approach, the results show a difference of casein micelle dispersion behavior between 7 and 20 °C: at 7 °C, casein micelles are less compressible, their sol-gel transition concentration is lower and they developed more cohesive interactions than at 20 °C. By the in-situ approach, the results show that it is possible to partially remove deposits accumulated during crossflow and frontal filtration by a pressure relaxation. The deposit is removed likely by swelling of the casein micelle gel with diffusion of the solvent
together in the bulk side (retentate part) and near the membrane surface (permeate part). These results allow to consider new perspectives of the rinsing and cleaning steps of membranes
Disease resistant bouquet vine varieties: assessment of the phenolic, aromatic, and sensory potential of their wines
No full textThe search for grape varieties resistant to diseases and to climatic changes notably concerns the wine industry. Nine monovarietal wines from new red grape varieties resistant to cryptogamic diseases (downy and powdery mildews) were evaluated in terms of their total phenolic, anthocyanin and proanthocyanidin contents, anthocyanin profile, volatile composition, and sensory attributes. Thus, the question remains, will these hybrid grapes (>= 97.5% of Vitis vinifera genome) lead to wines with organoleptic properties similar to those of Vitis vinifera wines that consumers are used to? Total phenolic (1547-3418 mg GA/L), anthocyanin (186-561 mg malvidin/L), and proanthocyanidin (1.4-4.5 g tannins/L) contents were in broad agreement with those previously described in the literature for monovarietal wines produced with well-known red grape varieties (Cabernet Sauvignon, Merlot, Syrah). With regard to fruity aroma, ethyl esters of straight-chain fatty acids (530-929 mu g/L) stood out clearly as the major volatile components for all hybrid wines considered. Sensory analysis revealed significant differences (p < 0.05) for visual aspect, aroma, flavor, global balance, astringency, and body. Overall, these new hybrid grape varieties are not only resistant to cryptogamic diseases, but also present enough potential to become quality wines, since their phenolic and volatile attributes are close to those of common red monovarietal wines
Differential susceptibility to the mycoparasite Paraphaeosphaeria minitans among Sclerotinia sclerotiorum isolates
No full textThe mycoparasitic fungus Paraphaeosphaeria minitans (formerly Coniothyrium minitans), is increasingly used by farmers to reduce soilborne inoculum of Sclerotinia sclerotiorum. In France, its field efficacy tends to be higher in the North than in the South, leading to the hypothesis of possible regional differences in the susceptibility of the pathogen to the biocontrol agent. A standardized assay was developed and four quantitative criteria were used to assess the susceptibility to P. minitans of 75 S. sclerotiorum isolates collected from different regions of France. There was no significant difference between the group of isolates from the North and that from the South, but wide differences were observed among isolates, with consistent responses for all quantitative criteria. This study suggests that biocontrol efficacy might vary locally depending on the frequency of less susceptible isolates and it brings to attention the possibility that selection pressure could lead to a gradual increase in the frequency of less susceptible isolates, as this biocontrol method becomes widely adopted by farmers. To our knowledge, this is the first report of the variable susceptibility of S. sclerotiorum to a commercialized strain of P. minitans and the first detailed characterization of a large group of isolates from France for traits related to fitness, such as mycelial growth and production of sclerotia
Serological evidence of infection with dengue and Zika viruses in horses on French Pacific Islands
No full textNew Caledonia and French Polynesia are areas in which arboviruses circulate extensively. A large serological survey among horses from New Caledonia and French Polynesia was carried out to investigate the seroprevalence of flaviviruses in the horse population. Here, 293 equine sera samples were screened for flaviviruses using a competitive enzyme-linked immunosorbent assay (cELISA). The positive sera were then confirmed using a flavivirus-specific microsphere immunoassay (MIA) and seroneutralization tests. This serosurvey showed that 16.6% (27/163) and 30.8% (40/130) of horses were positive for cELISA tests in New Caledonia and French Polynesia, respectively, but the MIA technique, targeting only flaviviruses causing neuro-invasive infections in humans and horses (i.e. West Nile virus [WNV], Japanese encephalitis virus [JEV] and tick-borne encephalitis virus [TBEV]), showed negative results for more than 85% (57/67) of the cELISA-positive animals. Seroneutralization tests with the main flaviviruses circulating in the South Pacific revealed that 6.1% (10/163; confidence interval [95% CI] 3.0%-11.0%) of sera in New Caledonia and 7.7% (10/130; 95% CI 3.8%-13.7%) in French Polynesia were positive for dengue virus serotype 1 (DENV1) and 4.3% (7/163; 95% CI 1.7%-8.6%) in New Caledonia and 15.4% (20/130, 95% CI 9.7%-22.8%) in French Polynesia were found positive for Zika virus (ZIKV). Seroprevalence of the JEV and WNV flaviviruses on the 293 samples from both island groups were comparatively much lower (less than 2%). This seroprevalence study in the horse population shows that horses can be infected with dengue and Zika viruses and that these infections lead to seroconversions in horses. The consequences of these infections in horses and their role in ZIKV and DENV epidemiological cycles are two issues that deserve further investigation. Author summary New Caledonia and French Polynesia, located in the South Pacific, are facing circulation of dengue virus (DENV) for a long time and emergence of Zika virus (ZIKV) since 2013. A large serosurvey among horses' population from these two islands was carried out to investigate the seroprevalence of the main flaviviruses circulating in the South Pacific. We find out that 6 to 7% of equine sera tested were positive for DENV serotype 1 in the two islands and 4% and 15% were positive for ZIKV in New Caledonia and French Polynesia respectively. Our study highlighted serological evidence of DENV serotype 1 and ZIKV infections of horses leading to meaningful seroconversion. Seroprevalence of other mosquito-borne flaviviruses (i.e. Japanese encephalitis and West-Nile viruses) were comparatively much lower (less than 2%) in New Caledonia and French Polynesia groups suggesting the absence of past active circulation of these viruses in both islands. This finding emphasized the need to investigate the consequences of such infections in the horse population and to determine the role of domestic animals in ZIKV and DENV epidemiological cycles
Alteration of erythrocyte membrane polyunsaturated fatty acids in preterm newborns with retinopathy of prematurity
No full textExtremely preterm infants are at high risk for retinopathy of prematurity (ROP), a potentially blinding disease characterized by abnormalities in retinal vascularization. Whereas animal studies revealed that n-3 polyunsaturated fatty acids (PUFAs) may be of benefit in preventing ROP, human studies conducted on preterm infants during the 1st weeks of life showed no association between blood n-3 PUFA bioavailability and ROP incidence and/or severity, probably because of the influence of nutrition on the lipid status of infants. In the OmegaROP prospective cohort study, we characterized the erythrocyte concentrations of PUFAs in preterm infants aged less than 29 weeks gestational age (GA) without any nutritional influence. We show that GA is positively associated with the erythrocyte n-6 to n-3 PUFA ratio, and particularly with the ratio of arachidonic acid (AA) to docosahexaenoic acid (DHA), in infants with ROP. A time-dependent accumulation of AA at the expense of DHA seems to occur in utero in erythrocytes of preterm infants who will develop ROP, thus reinforcing previous data on the beneficial properties of DHA on this disease. In addition, preliminary data on maternal erythrocyte membrane lipid concentrations suggest modifications in placental transfer of fatty acids. Documenting the erythrocyte AA to DHA ratio at birth in larger cohorts might be useful to set up new prognostic factors for ROP
Willingness-to-pay of anglers for catch-and-release: results from a choice experiment in Britanny
No full textIn 2017, a survey of salmon anglers was conducted in three départements in West Brittany to ascertain their willingness to pay for different fishing management parameters: season, total allowable catch (TAC), fishing method, catch and release, and level of river use. The anglers were asked to choose between hypothetical fishing destinations, differing in terms of their combination of management parameters and travel distance. On average, we observe that catch and release has a depressive effect on the valuation of a day’s fishing, at €25 per day if removal is allowed and €15 per day if catch and release is compulsory. However, some socioeconomic groups (the most qualified) positively value catch and release. All in all, it is of note that the majority of the anglers nonetheless hold a positive valuation of a catch-and-release fishing day, which could therefore be used to generate economic returns for the river after the close of the TAC. Lastly, the fishing season, and especially the level of river use, impact more on the value of fishing than catch and release
Mapping plant diversity in cocoa-based agroforestry systems to improve overall productivity
No full textPopulation genetics and genotyping as tools for planning rat management programmes
No full textBrown rats are a prolific synanthropic pest species, but attempts to control their populations have had limited success. Rat population dynamics, dispersal patterns, and resistance to rodenticides are important parameters to consider when planning a control programme. We used population genetics and genotyping to investigate how these parameters vary in contrasting landscapes, namely one urban and two rural municipalities from eastern France. A total of 355 wild brown rats from 5 to 6 sites per municipality were genotyped for 13 microsatellite loci and tested for mutations in the Vkorc1 gene which confers resistance to some rodenticides. Results revealed a strong genetic structure of the sampled rat populations at both regional (between municipalities) and local (between sites within municipalities) levels. A pattern of isolation by distance was detected in the urban habitat and in one of the rural municipalities. GeneClass and DAPC analyses identified 25 (7%) and 36 (10%) migrants, respectively. Migrations occurred mostly between sites within each municipality. We deduced that rat dispersal is driven by both natural small-scale movements of individuals and longer-distance (human-assisted) movements. Mutation Y139F on gene Vkorc1 was significantly more prevalent in rural (frequency 0.26-0.96) than in urban sites (0.00-0.11), likely due to differences in selection pressures. Indeed, pest control is irregular and uncoordinated in rural areas, whereas it is better structured and strategically organised in cities. We conclude that simultaneous pest control actions between nearby farms in rural habitats are highly recommended in order to increase rat control success while limiting the spread of resistance to rodenticides