Biomedical subjects

Martine Le Meste

Publications and source records attributed to Martine Le Meste.

3 recordsLinked to original sources

PubMed2004

Ascorbic acid oxidation in sucrose aqueous model systems at subzero temperatures.

The reduction of Tempol by ascorbic acid in concentrated sucrose solutions was measured by electron paramagnetic resonance (EPR) at temperatures ranging from 16 to -16 degrees C. This method allowed the determination of the rate constants (k) of this fast reaction, by recording the Tempol reduction as a function of time. The two reactants were initially separated and had to migrate for the reaction to occur. The experimental findings were compared with predicted values according to the equation for diffusion-controlled reaction proposed by Atkins. The experimental reaction rate constants were observed to be lower than the calculated ones. However, the experimental values were found to be controlled by the temperature and viscosity changes of the reaction media, as expected for a diffusion-controlled reaction.

Ascorbic Acid↗

PubMed2002

Study of release kinetics of small and high molecular weight substances dispersed into spray-dried ethylcellulose microspheres.

Spray-dried ethylcellulose microspheres were used as matrices for the encapsulation of a fungal lactase and/or small paramagnetic probes (Tempol or Tempo). Their dissolution in water was studied. Kinetics fitted with the model Q = kt(n) of Korsemeyer et al. [Int. J. Pharm. 15 (1983) 25] exhibited a non-Fickian diffusion. The calculated diffusional exponent (n) values were near 0.26 whatever the encapsulated probes. The release rates (k) were only slightly different for paramagnetic probes and lactase. This result indicated that the probes' release mechanisms are not diffusion controlled. Other factors such as matrix porosity and probe solubility in the matrix and in water could influence the probes' release rate.

Cellulose↗

PubMed2002

Effect of sodium chloride on the gelatinization of starch: a multimeasurement study.

The effect of sodium chloride on the gelatinization and rheological properties of wheat and potato starches has been studied using differential scanning calorimetry, dynamic mechanical thermal analysis, and electron spin resonance techniques. All samples contained 60% water (w/w wet starch basis) and the salt content ranged from 0 to 16% (g/100 g starch-water). The presence of salt affected the onset (T(o)), peak (T(p)), and end (T(e)) temperatures of gelatinization, gelatinization enthalpy (DeltaH), storage modulus (G'), and rotational mobility coefficient (D(rot)), and the effect differed by salt concentration. 1H-NMR was used in parallel in order to elucidate how salts affect the properties of water in starch suspensions and in aqueous salt solutions according to their position on the Hofmeister series classification. The obtained results suggest that the mechanism of starch gelatinization in salt solutions can be attributed to the effect of solute on water properties and direct polymer-solute interactions. These two effects conflict with one another and result in complex effect patterns depending on the concentration of the salts.

Biopolymers↗