Three classes of starch granule swelling: Influence of surface proteins and lipids

The role of non-carbohydrate surface components of granular starch in determining gelatinisation behaviour has been tested by treatment of native starches with a range of extractants. Resulting washed starches were analysed for (bio)chemical, calorimetric and theological properties. Sodium dodecyl sulphate (SDS) was the most efficient extractant tested, and resulted in major changes to the subsequent theological properties of wheat and maize starches but not other starches. Three classes of starch granule swelling behaviour are identified: (i) rapid swelling (e.g. waxy maize, potato), (ii) slow swelling that can be converted to rapid swelling by extraction of surface proteins and lipids (e.g. wheat, maize), and (iii) limited swelling not affected by protein/lipid extraction (e.g. high amylose maize/potato). Comparison of a range of extractants suggests that all of protein, lipid and amylose are involved in restriction of swelling for wheat or maize starches. Treatment of starches with SDS leads to a residue at comparable (low) levels of SDS for all starches. C-13 NMR analysis shows that this SDS is present as a glucan inclusion complex, even for waxy maize starch. We infer that under the conditions used, glucan inclusion complexation of SDS is equally likely with amylopectin as with amylose. (c) 2006 Elsevier Ltd. All rights reserved

Distribution of carbon 14 in the terrestrial environment close to French nuclear power plants

For 10 years, 14C measurements have been performed around French nuclear power plant sites, both in zones influenced and zones not influenced by gaseous releases. Examining the results from these measurements in the terrestrial environment shows that the discharges have a very slight impact on the radiocarbon level (with a relative increase in the specific activity of the order of 3 Bq kg-1 C in the influenced areas). In correlation, there is a near-negligible increase in dose, on average less than 0.1 μSv yr -1, with reference to a dose from background radiation, which is of the order of 10 μSv yr-1. The δC13 values are very similar between the influenced zone and the non-influenced zone, with a mean of -27‰. The mean ΔC14 varies from 101‰ in the non-influenced zone to 123‰ in the influenced zone. Moreover, a general reduction in 14C concentration was found, with a time constant of the order of 95 years. The current level of 14C specific activity in terrestrial environment is estimated to be 242 ± 6 Bq kg-1 C. © 2005 Elsevier Ltd. All rights reserved

Influence d'acides organiques sur la désorption de l'américium 241 et du neptunium 237 à partir d'un sol cultivé acide

Effect of organic acids on 241 americium and 237 neptunium desorption from an acidic cultivated soil. Naturally occurring organic substances have been recognised as one important factor affecting the behaviour in the environment of transuranic actinides. This experimental study aims at evaluating if some naturally occurring carboxylic acids (vanillic, citric, lactic, oxalic) would affect 241Am or 237Np availability in an acidic agricultural soil. Data show that these acids enhance the desorption of americium and neptunium from the soil, with a noticeable effect of citric acid. The fraction desorbed is multiplied by more than 10 for 0.1 M citric acid, and by 3 or 4 with other acids, in relation with the complexation of radionuclides with these acids. The desorption increases with molar concentration of the acids because of the decrease of pH in acidified soils, except for oxalic acid. The soil moisture conditions seem to affect the desorption results: the percentage desorbed is approximately 10 times lower for batch experiments (saturated conditions) than for centrifugation corresponding to unsaturated soil conditions. These preliminary data are mainly qualitative, but they show that it could be interesting to take into account more realistic physico-chemical conditions when measuring desorption ratios for cultivated soils

Mesure du plutonium dans des échantillons de sols et de sédiments prélevés en juin 1991 autour du site de la centrale de Creys-Malville

Le plutonium a été mesuré, en 1991, sur 5 échantillons de sols et 12 échantillons de sédiments du Rhône prélevés autour du site de la centrale électronucléaire de Creys-Malville. Les concentrations des sols (fraction tamisée à 2 mm) varient, pour 239+240Pu, de 35 ± 4 à 1411 ± 135 mBq.kg-1 sec et, pour 238Pu, de moins de 1 à 101 ± 6 mBq.kg-1 sec. Dans les sédiments, on observe de l7 ± 4 à 147 ± 12 mBq.kg-1 sec en 239+240Pu et de moins de 1 à 7,2 ± 1,6 mBq.kg-1 sec en 238Pu. Ces résultats sont du même ordre que les résultats de mesures de plutonium faites, à ce jour, dans l'environnement français et les rapports isotopiques 238Pu/239+240Pu sont analogues à ceux des retombées atmosphériques (0,03 à 0,08) et sont différents des rapports caractéristiques de l'usine (0,7 à 0,8). La variabilité des résultats selon les échantillons confirme que la fixation du plutonium sur les sols et les sédiments dépend, pour une large part, des teneurs de ces substrats en matière organique et en particules fines