Effect of oxidoreduction potential and of gas bubbling on rheological properties and microstructure of acid skim milk gels acidified with glucono-delta-lactone

Milk oxidoreduction potential was modified using gases during the production of a model dairy product and its effect on gel setting was studied. Acidification by glucono-δ-lactone was used to examine the physicochemistry of gelation and to avoid variations due to microorganisms sensitive to oxidoreduction potential.Four conditions of oxidoreduction potential were appliedto milk: milk was gassed with air, nongassed, gassed with N2, or gassed with N2H2. The rheologicalproperties and microstructure of these gels were determined using viscoelasticimetry, measurement of whey separation, and confocal laser scanning microscopy. It appeared that a reducing environment led to less-aggregated proteins within the matrix and consequently decreased whey separation significantly. The use of gas to modify oxidoreduction potential is a possible way to improve the quality of dairy products

Two Cases of Dogs with Infiltrative Lipomas of the Thigh Region

Two Cases of Dogs with Infiltrative Lipomas of the Thigh Regio

2 Cas de Lipomes Infiltrants de la Cuisse

Malgré la bonne connaissance des lipomes par le vétérinaire, les lipomes infiltrants et les autres tumeurs du tissu adipeux restent méconnus. Ces cas illustrent le diagnostic et le traitement des lipomes infiltrants

18- The reducing power of LAB in fermentation and biomass production

International audienceLactic acid bacteria (LAB) are found in highly variable environments. Among the various parameters that characterize these environments, the redox state has already been indirectly addressed in studies on the impact of oxidative stress. Nevertheless, it is possible to offer a broader vision about the capacity of LAB to extracellular electron transfer. The metabolism of LAB, which are chemotrophic organisms, involves a series of reactions of dehydrogenation (oxidation) and hydrogenation (reduction). This metabolism obeys the principle of conservation of energy and matter, and therefore it requires the availability of a final electron acceptor; in LAB a carbon intermediate will be reduced. The vision of perfect coupling, which is theoretically consistent, must however be qualified depending on environmental conditions, and in particular the redox state of the extracellular medium. This process is not without influence on metabolism fluxes, growth, and physicochemical environment in which the microorganism bathes. This multifactorial interaction system is a difficulty in studying extracellular electron transfer by lactic acid x, but also a subject of interest to understand better the redox activity of these microorganisms. The purpose of this chapter is to present how LAB manage their reducing power according to the redox environment

Chap. 7.2.2.1. Modified Atmosphere Packaging and Controlled Atmosphere Packaging : Effect of gases on microorganisms

International audienceNo abstrac

Bases scientifiques de la qualité du Venaco, fromage traditionnel au lait cru (mise au point de ferments sélectionnés spécifiques)

Cette thèse avait pour objectif de déterminer dans quelle mesure l'emploi de ferments sélectionnés spécifiques dans le fabrication d'un fromage traditionnel de Corse, le type Venaco, permet au fromager de mieux contrôler la cinétique d'acidification du fromage, contribue à conserver ses caractéristiques sensorielles spécifiques. Les principaux résultats sont les suivants : Une enquête a mis en évidence que la plupart des fromagers interrogés sont intéressés par l'usage de ferments spécifiques. L'identification et la caractérisation des souches locales isolées a permis de constituer une collection de bactéries lactiques. L'expérimentation réalisée dans les fromageries a conduit à la mise au point de ferments sélectionnés spécifiques qui apportent une garantie en terme d'acidification, pouvant inhiber la croissance des germes d'altération et pathogènes. Les souches ensemencées dans le lait s'implantent durablement. La microflore naturelle, notamment lactique, se développe également pendant l'affinage, ce qui traduit un certain équilibre entre les ferments et cette microflore. Sur le plan sensoriel, les fromages fabriqués avec des ferments spécifiques sont, dans la plupart des cas, significativement différents des témoins élaborés avec des ferments industriels ou CNRZ, probablement à cause d'une modification des degrés de lipolyse et de protéolyse. Basée sur la participation directe des fromagers, cette démarche originale a abouti à la mise au point d'un outil pertinent pour maîtriser la qualité du fromage et maintenir son identité, face à l'évolution des écosystèmes microbiens dans les fromageries.DIJON-BU Sciences Economie (212312102) / SudocSudocFranceF

Optimisation de l'utilisation des Leuconostoc au cours de la fabrication du roquefort

DIJON-BU Sciences Economie (212312102) / SudocSudocFranceF

Ion-selective electrode integrated in small-scale bioreactor for continuous intracellular pH determination in Lactobacillus plantarum

International audienceThe aim of the present study was to develop an ion-selective electrode method for the continuous determination of the intracellular pH in Lactobacillus plantarum using a small-scale bioreactor. This method employed a salicylate-selective electrode basing on the distribution of salicylic acid across the cytoplasmic membrane. This developed electrode responded to salicylate concentrations above 20 μmol/L with a Nernstian sensitivity. The energized and concentrated cells were added into a thermostated small-scale bioreactor that contained the salicylate anions dissolved in a 100 mmol/L potassium phosphate buffer at different pH values. The changes in salicylate concentration that occurred in the medium containing bacterial suspension were measured as a voltage change. The cells of Lactobacillus plantarum showed maintenance of pH homeostasis at the studied pH ranging from 4.0 to 7.0, and they kept a neutral intracellular pH up to 5.8. The simplicity of the measuring preparation and the relatively low cellular concentration, as well as the advantages of the small-scale bioreactor, lead us to believe that the described method can facilitate the study of the physicochemical factors on the intracellular pH of lactic acid bacteria using a single pH probe in one method

Impacts de modifications du potentiel d'oxydoréduction par des gaz sur les aptitudes technologiques des bactéries lactiques

DIJON-BU Sciences Economie (212312102) / SudocSudocFranceF