Eric W. Sydenham

Reduction of patulin in apple juice samples — influence of initial processing

Abstract Patulin is a secondary metabolite produced by a wide range of fungi including Penicillium expansum, a common contaminant of apples. Patulin is reputed to be a mutagen and recommendations have been made that levels should not exceed 50 ng g in apple juice intended for human consumption. The production of apple juice requires the use of ripe fruit, which may be pre-disposed to fungal contamination with P. expansum and concurrent contamination with patulin. During a study using selected over-ripe fruit, triplicate samples of apples were withdrawn at several points prior to maceration. The mean patulin level in the non-processed fruit was found to be 920 ng g , but this level dropped to 190 ng g following an initial water treatment step. Analyses of the wash water showed that appreciable levels had been transferred from the solid to the aqueous phase. Additional removal, by hand, of rotten and damaged fruit prior to further processing, significantly reduced the mean patulin level in the juice to 55 ng g . High patulin levels were recorded in the rotten fractions ( mean = 2335 ng g ). Mycological analyses tended to support the chemical data, in that removal of the rotten fruit significantly reduced the total fungal counts in the juice samples.

Natural co-occurrence of fumonisins, deoxynivalenol, zearalenone and aflatoxins in field trial corn in Argentina.

Corn samples collected from the main production area in Argentina in 1995 were surveyed for the natural occurrence of Fusarium mycotoxins and aflatoxins. Fumonisins B1, B2 and B3 and zearalenone were found in all samples. A positive relationship was found between fumonisins B1, B2 and B3, B1 and B3, and B2 and B3. Deoxynivalenol and aflatoxins were not detected. Mycological survey has also revealed the predominance of Fusarium moniliforme. This is the first report on the simultaneous occurrence of fumonisins and zearalenone in corn from the main production area in Argentina.

Biliary excretion of the mycotoxin fumonisin B1 in rats

The biliary excretion of the mycotoxin fumonisin B1 (FB1), produced by the fungus Fusarium moniliforme Sheldon, has been measured in male Wistar rats. After ip injection of a solution of FB1 (7.5 mg/kg body weight), 67% of the applied dose was recovered in bile over a 24-hr period, 88% of this recovery being excreted in the first 4 hr after dosing. In contrast to these results, a similar dose of FB1 given by gavage resulted in only 0.2% recovery of the toxin in bile over a 24-hr period. Hence, although these results show that biliary excretion is a major route of elimination of FB1 from the circulation, only small amounts of the toxin appeared to be absorbed from the gut in rats.

Toxicokinetics of the mycotoxin fumonisin B2 in rats

Fumonisin B2 (FB2), a secondary metabolite of the fungus Fusarium moniliforme, was administered at a dose of 7.5 mg/kg body weight to male BD IX rats by ip injection or by gavage. FB2 was rapidly absorbed from the peritoneum, its level in plasma reaching a maximum within 20 min after injection. It was rapidly eliminated from plasma with a half-life of 26 min. After 24 hr, FB2 could not be detected in plasma (< 20 ng/ml). Analysis of rat plasma for FB2 following a gavage dose failed to detect any toxin over a 6-hr period after dosing. The elimination of FB2 in the urine and faeces was determined over a 3-day period after dosing. After i.p. injection, the mean urinary excretion over this period was 1.2% and faecal elimination accounted for 84.1% of the dose. Similarly, after dosing by gavage, 0.2 and 82.0% of the dose was recovered in urine and faeces, respectively. FB2 appeared to be excreted unmetabolized.

Liquid chromatographic determination of the mycotoxin fumonisin B2 in physiological samples

The fungus Fusarium moniliforme produces a group of mycotoxins, the fumonisins, of which the most abundant are fumonisins B1 (FB1) and B2 (FB2). Previously developed analytical methods for the determination of FB1 in physiological samples have been modified for the determination of FB2 by the use of less polar extraction solvents. Plasma and urine extracts were purified on strong anion-exchange solid-phase extraction cartridges and fecal extracts on reversed-phase (C18) cartridges. FB2 in purified extracts was determined by reversed-phase HPLC with fluorescence detection using performed o-phthaldialdehyde derivatives. These methods were reproducible (R.S.D. of less than 6%) with recoveries greater than 85%. In a short preliminary study, they have been applied to the determination of the fate of FB2 dosed to rats by gavage. Of the dose given to the animals, over 90% was recovered unmetabolised in the feces within 48 h.

Determination of fumonisins in corn: Evaluation of two purification procedures.

The performance of two solid phase extraction (SPE) purification procedures, used in the determination of fumonlsin B1 (FB1), B2 (FB2) and B3 (FB2) In corn, was evaluated using both thin-layer chromatography (TLC) and high performance liquid chromatography (HPLC). Fewer interferences were observed In extracts prepared using the strong anion exchange (SAX) media, in contrast to those purified on C18 media, where on occasions, visual discernment of the TLC bands was hampered by the presence of interfering compounds. Precipitate formation, resulting In the blocking of SPE cartridges was also encountered when using the C18 procedure. HPLC analyses of extracts prepared by both media indicated that they gave comparable fumonlsin recoveries from naturally contaminated corn samples. The results suggest that the C18 procedure, originally developed for the TLC analyses of FB1 in mixed feeds, may also be applied to the determination of FB2 and FB2. However, where TLC is used quantitatively for fumonlsin levels <1 μg/g, purification of sample extracts on SAX media is recommended.

Fumonsin B1, B2, and B3 content of commercial unprocessed maize imported into South Africa from Argentina and the USA during 1992

The widespread occurrence of F. moniliforme and the toxic effects of its secondary metabolites, the fumonisins B1(FB1), B2(FB2) and B3(FB3), make it imperative that fumonisin contamination of maize, a major constituent of animal feed as well as the staple diet of many populations, be closely monitored to reduce the risk of fumonisin exposure. Equine leukoencephalomalacia and porcine pulmonary oedema have been associated with the intake of feed heavily contaminated with fumonisins. In addition, high levels of fumonisins in the maize-based staple diets of certain populations have been linked to a high incidence of oesophageal cancer in the Transkei region of South Africa and in Linxian and Cixian Counties, China. Bulk shipments of maize imported into South Africa from the USA and Argentina during 1992 were sampled at the port of entry to determine fumonisin levels. Of the 79 samples from two US shipments, all were positive for fumonisins, with FB1 constituting approximately 71% of the total fumonisins with an overall mean of 2.35 micrograms/gFB1. The maximum FB1 level observed was 3.9 micrograms/g. These levels contrast with those obtained from two Argentinian bulk shipments, which also were all positive for fumonisins, but had a mean FB1 level of 0.31 microgram/g and a maximum observed level of 0.7 microgram/g FB1 measured over 47 composite samples.

The Reliability and Significance of Analytical Data on the Natural Occurrence of Fumonisins in Food

Several methods are presently used to identify and quantify fumonisins in foods and feeds. HPLC procedures on derivatized fumonisins with fluorescence detection are most commonly used. The validity and significance of reported fumonisin levels depend on several factors such as the specificity, detection limit, accuracy and reproducibility of the analytical method as well as on the sampling procedure used, and the integrity and purity of the analytical standards. The importance of these factors is discussed and the results of two international collaborative studies are presented on the determination of fumonisins in corn by a reversed-phase HPLC method on o-phthaldialdehyde (OPA) derivatized fumonisins using fluorescence detection.