Search

Peritoneal dialysis (PD) is commonly performed by using preprepared dialysis solutions containing glucose, which are thermally treated to achieve commercial sterilization. A series of glucose degradation products (GDPs) are being formed, which react with the tissue during the dialysis procedure, thus baring a negative effect on the patient and the dialysis process. The present study tested the efficacy of ohmic heating as an alternative thermal treatment for continuous sterilization of PD solutions. The process was compared to conventional retort treatment, and GDPs accumulation was measured. Thermal treatments using the ohmic heating system were performed at three temperatures (105, 125, and 150 degrees C) with residence time at each temperature ranging from 0.84 to 12.0 s. The resulting concentrations of glyoxal (GO), methylglyoxal (MGO), and 3-deoxyglucosone (3-DG) in the PD solutions were measured. None of these GDPs were found in PD fluids treated by ohmic heating at 105 degrees C. The concentration of 3-DG, after a standard sterilization treatment (121 degrees C, 20 or 40 min) was one order of magnitude higher (approximately 140 and 242 microM) than after ohmic heating treatment at 125 degrees C. The results of the present study suggest that this technique can be used to produce solutions with much lower content of GDPs. It also demonstrates the advantage of using the ohmic heating technology as a tool for high temperature short time treatment of PD fluids.

Soy isoflavones, present in many processed soy foods, are known for their phytoestrogenic and antioxidant activities. The aim of this work was to study the kinetics of genistein and daidzein degradation at elevated temperatures and to follow changes in their antioxidant activity. Daidzein and genistein in model solutions (pH 7 and 9) were thermally treated at 120 degrees C or incubated at 70, 80, and 90 degrees C. Isoflavone degradation was observed at all temperatures, with apparent first-order kinetics at 70-90 degrees C, and E(a) = 8.4 and 11.6 kcal/mol at pH 9, respectively. Microcalorimetric stability tests showed a similar pattern of degradation, however, with higher E(a) (genistein, 73.7 kcal/mol; daidzein, 34.1 kcal/mol) that may be attributed to the anaerobic conditions. The antioxidant activity of incubated isoflavone solutions, followed by the ABTS test, decreased rapidly at pH 9 for genistein, whereas only moderate reduction was observed for daidzein (pH 7 and 9) or genistein at pH 7. This may indicate different degradation mechanisms for genistein and daidzein.