Objective Bioincompatible glucose degradation products (GDPs) develop during heat sterilization of peritoneal dialysis (PD) fluids. However, degradation may also take place during storage. Consequently, storage may add to the bioincompatibility caused by heat sterilization. The aim of the present study was to investigate how different factors such as the sterilization procedure, pH, glucose concentration, and temperature influence GDP production during storage. Design Degradation in glucose solutions was followed by pH and UV absorbance at 228 nm and 284 nm over 2 years of storage. Different sterilization times, storage temperatures, pH, and glucose concentrations were included in the study. Peritoneal dialysis fluids were also used in the experiment. Bioincompatibility was estimated through inhibition of cell growth in L-929 fibroblasts, and GDPs through UV absorption and liquid chromatography. Results The most important factor determining the rate of GDP production during storage was temperature. The GDPs created by heat sterilization promoted further degradation of glucose during subsequent storage. A pH of around 3.2 protected glucose from degradation during both heat sterilization and storage. At a storage temperature of 20°C and a pH of 3.2, degradation was almost negligible. Heat sterilization produced considerable amounts of GDPs absorbing at 228 nm. During initial storage, these 228 nm-absorbing GDPs almost disappeared. After reaching a nadir, absorbance at 228 nm again started to increase. Contrary to this, absorbance at 284 nm [caused mainly by 5-hydroxymethyl-2-furaldehyde (5-HMF)] increased during the whole storage period. After 2 years at 40°C, the concentrations of GDPs produced during storage were of the same magnitude as those caused by heat sterilization. Inhibition of cell growth of L-929 fibroblasts correlated well with the part of the absorbance at 228 nm not caused by 5-HMF in glucose solutions that were heat sterilized under a wide range of conditions. This part of 228 nm absorbance (denoted 228corr) was caused almost entirely by 3,4-dideoxyglucosone-3-ene (3,4-DGE). Conclusions Temperature is the single most important factor for glucose degradation during storage. The concentrations of bioincompatible GDPs produced may, under improper conditions, be as high as those produced during sterilization. High concentrations of glucose and low pH protect glucose from being degraded during both sterilization and storage. A good estimate of 3,4-DGE concentration in the fluids can be obtained correcting the UV absorbance at 228 nm for the influence from 5-HMF (and, when appropriate, for lactate). The 228corr may thus be used as a simple quality control for the fluids.

Objective Fluids for peritoneal dialysis (PD) cause cytotoxic reactions in many different in vitro systems. The low pH, the high osmolality of the fluids, and the glucose degradation products formed during heat sterilization have been considered responsible. In the present study, we investigate the influence of temperature and time during heat sterilization of PD fluids and glucose solutions on glucose degradation and cytotoxicity of the solutions. Design Ampoules containing PD-fluid or glucose solution were heated in an oil bath to predetermined F o values (combinations of time and temperature giving equal energy/bacteriallethality). Cytotoxicity of the solutions was measured as groWth inhibition of cultured L-929 fibroblasts. Glucose degradation was measured as UV absorbance at 228 and 284 nm. Results The same general pattern was seen in both PD fluid and glucose solution. Cytotoxicity decreased from 90% to 15% when the sterilization temperature was increased from 115° to 140°C and concomitantly the length of time shortened in order to maintain equal bacteriallethality. Under the same conditions, degradation products, measured as UV absorbance at 284 nm, decreased from 0.2 to 0.02. Conclusion To minimizethe development of cytotoxic breakdown products, high temperatures over short periods of time should be used to heat-sterilize PD fluids. Even as small an increase as 5°C at around 120°C will improve the quality of the solutions.

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Objective When glucose is present in a medical fluid, the heat applied during sterilization leads to degradation. The glucose degradation products (GDPs) give rise to bioincompatible reactions in peritoneal dialysis patients. The extent of the degradation depends on a number of factors, such as heating time, temperature, pH, glucose concentration, and catalyzing substances. In the present work, we investigated the influence of pH and concentration in order to determine how to decrease the amounts of GDPs produced. Design Glucose solutions (1% - 60% glucose; pH 1 - 8) were heat sterilized at 121°C. Ultraviolet (UV) absorption, aldehydes, pH, and inhibition of cell growth (ICG) were used as measures of degradation. Results Glucose degradation was minimum at an initial pH (prior to sterilization) of around 3.5 and at a high concentration of glucose. There was considerable development of acid degradation products during the sterilization process when the initial pH was high. Two different patterns of development of UV-absorbing degradation products were seen: one below pH 3.5, dominated by the formation of 5-hydroxy-methyl-2-furaldehyde (5-HMF); and one above, dominated by degradation products absorbing at 228 nm. 3-Deoxyglucosone (3-DG) concentration and the portion of 228 nm UV absorbance not caused by 5-HMF were found to relate to the in vitro bioincompatibility measured as ICG; there was no relation between 5-HMF or absorbance at 284 nm and bioincompatibility. Conclusion In order to minimize the development of bioincompatible GDPs in peritoneal dialysis fluids during heat sterilization, pH should be kept around 3.2 and the concentration of glucose should be high. 5-HMF and 284 nm UV absorbance are not reliable as quality measures. 3-DG and the portion of UV absorbance at 228 nm caused by degradation products other than 5-HMF seem to be reliable indicators of bioincompatibility.

The mycoflora of malt which caused gushing beer has been investigated and compared with the mycoflora of malt from nine malting plants in Sweden, Denmark, Finland and England. Malt which caused gushing beer was found to contain a high proportion of grains contaminated by Aspergillus, Penicillium and Rhizopus. The commonest species isolated were found to be Aspergiffus fumigatus and Aspergillus amstelodami. These fungi occurred on all malt samples investigated independent of their origin. The mycoflora on malt differs greatly from that found on barley. Evidence is presented showing that barley becomes contaminated during the malting process.