SynopsisElectron spin measurement of the local Cu++ concentrations have been performed in different cation exchange membranes by comparison with reference frozen aqueous solutions of Cu++ salts.Comparison of the obtained values with the average chemical concentrations has therefore permitted direct evidence of microphase separation in these systems. Local concentrations approximately four times larger than average chemical concentrations have been found. Information about composition of this ion-containing phase has also been obtained from changes in local Cu++ concentrations versus water content. INTRODUCTIONWe are interested in the microstructure of ion-containing polymers, especially in this paper of polymeric cation exchange membranes. Ion associations will generally depend on both ion concentration and the dielectric constant of the matrix. Small ionic associations called multiplets, involving a few ion pairs and larger aggregates, have to be considered when the dielectric constant of the matrix is sma1l.l In polymeric membranes, the situation is complicated because the ions of one sign are fixed on the chain leading to an excluded volume effect. Larger ionic associations are possible which give specific mechanical and physical properties to these materials. Knowledge of the microstructures of these membranes is therefore very important to explain membrane characteristics such as permselectivity, ionic conductivity, water diffusion, etc. Different experiments can be performed involving bulk properties measurements up to very local investigation of specific nuclei.The knowledge of the local ionic concentration and its comparison with the overall chemical concentration will be an efficient way to define a possible ionic phase segregation and to give information about its composition. The aim of this paper is to estimate the local Cu++ concentrations by electron spin resonance (ESR) measurements of different Cu++ neutralized cationic membranes. Small-angle neutron scattering experiments have shown that no drastic changeJournal of Applied Polymer Science, Vol. 28,1093-1103 (1983 change in the spectra is observed when varying the concentration (Fig. 1). A few empirical parameters such as the widths at half and quarter of maximum and relative heights of various components have been used to characterize the spectra, and their change vs. Cu++ concentrations have been plotted in Figures 2 and 3.The various reference solutions obtained by changing both the nature of the salt (sulfate, nitrate, and bromure) and the cryoprotector (dimethylsulfoxide, glycerol, ethyleneglycol) have given essentially the same results for the same Cu++ concentration. The changes observed from one spectrum to another are small compared to the changes observed with a small modification of the Cu++ concentration. We can therefore assume in first approximation that an ESR spectrum is characteristic of the Cu++ concentration. Because the dipole-dipole and exchange interactions are short range, the measured concentrations are local concentrati...

The fortification of dairy beverages is a widely developed strategy using non-heme or heme iron. Heme iron has a higher bioavailability. The investigation aimed to elaborate pasteurized milk with fortified chocolate flavor with heme iron that has good sensory acceptability. The preparation of the flavored milk was carried out based on the regulations and heme iron, obtained from a commercial source of whole blood of porcine origin, was added before the pasteurization process to achieve its complete dilution. The concentration of iron and chocolate flavoring was established as variables in order to evaluate the optimal formulation based on Sensory Acceptability (SA). The experimental design was a 32 factorial design in which eight formulations were established, which were sensory acceptability evaluated by a total of 35 school-age children, aged between 8 and 11 years using a five-point facial hedonic scale. The results of the analysis of variance and optimization of the response showed that SA was 4.71 (on a scale of 1 to 5) for a fortification of 6.76 mg Fe kg-1 sample and a chocolate concentration of 2.0 g kg-1 sample. The physicochemical characterization indicated a higher percentage of carbohydrates, a higher concentration of iron (9.3 mg Fe kg-1 sample) and vitamin C (349.0 mg kg-1 sample) with respect to fresh milk. According to the physicochemical and microbiological results, the approximate life time of the beverage was 5 days, which is in accordance with Peruvian regulations. These results showed a method of fortification of flavored milk that allowed the use of heme iron, whose content could contribute to the daily requirement of this mineral in children aged between 8 and 11 years old (8 mg of iron per day).