Enzyme activity and colour changes in apple juice pasteurised thermally and by pulsed electric fields

Pasteurisation of apple juice by a high temperature-short time treatment (HTST) at 90 °C for 30 s was compared with a high-voltage pulsed electric field treatment (PEF). The PEF treatment was carried out using a laboratory unit set with a bipolar pulse (4 μs wide), an intensity of 35 kV cm−1, and a frequency of 1200 pulses per second (pps). Enzyme inactivation and colour changes of the treated juices were compared, using a non-treated sample as control. Enzyme residual activities of pectinmethylesterase (PME) and polyphenoloxidase (PPO), as well as the chroma index for colour, showed statistical difference between treatments. No statistical significant difference was observed for the hue colour index. PEF could be considered a feasible alternative for producing pasteurised and stable apple juice

Iron influence on uranium removal from water using cellulose acetate membranes doped with activated carbon

International audienceUltrafiltration removal of uranium from water was investigated using cellulose triacetate-activated carbon (CTA-AC) composite membranes. Two different approaches were adopted: (i) adding iron chloride to the uranyl solution (FeCl3 at 0.5, 1.0, and 2.0ppm), and (ii) filtration of pure uranyl nitrate throughout composite membranes made of CTA filled with AC doped with iron. The solution to be filtrated was mixed with uranyl nitrate dissolutions at very low concentration (1.2ppm), with pH 6-8. AC was added to CTA using a casting film process to obtain dense membranes. Average uranium removal was 22 +/- 3%. The presence of iron in the membrane, either dissolved or incorporated into the activated carbon, contributed to uranium filtration, allowing reaching up to 50% removal efficiency (RE). The lowest RE value (4%) was obtained using a membrane prepared with AC oxidized with nitric acid (3HNO-AC) which does not present a significant amount of iron. Another parameter driving uranium transport is the pH, as uranium forms high molecular weight compounds in alkaline solutions, and therefore remains trapped into membrane structure. This explains the RE value of 21%, using 3HNO-AC membrane at high pH. AC dispersion also plays an important role during uranium transport. If it is well dispersed into the polymeric matrix, high RE is attained due to the high surface area available into the material. On the contrary, if AC agglomerates, uranium can go throughout the membrane, thereby increasing its permeability