Sonia Marín

Mycotoxins: occurrence, toxicology, and exposure assessment.

Mycotoxins are abiotic hazards produced by certain fungi that can grow on a variety of crops. Consequently, their prevalence in plant raw materials may be relatively high. The concentration of mycotoxins in finished products is usually lower than in raw materials. In this review, occurrence and toxicology of the main mycotoxins are summarised. Furthermore, methodological approaches for exposure assessment are described. Existing exposure assessments, both through contamination and consumption data and biomarkers of exposure, for the main mycotoxins are also discussed.

Inhibitory effect of cinnamon, clove, lemongrass, oregano and palmarose essential oils on growth and fumonisin B1 production by Fusarium proliferatum in maize grain

The effect of cinnamon, clove, oregano, palmarose and lemongrass oils on growth and FB1 production by three different isolates of F. proliferatum in irradiated maize grain at 0.995 and 0.950 aw and at 20 and 30 degrees C was evaluated. The five essential oils inhibited growth of F. proliferatum isolates at 0.995 aw at both temperatures, while at 0.950 aw only cinnamon, clove and oregano oils were effective in inhibiting growth of F. proliferatum at 20 degrees C and none of them at 30 degrees C. Cinnamon, oregano and palmarose oils had significant inhibitory effect on FB1 production by the three strains of F. proliferatum at 0.995 aw and both temperatures, while clove and lemongrass oils had only significant inhibitory effect at 30 degrees C. No differences were found using 500 or 1000 microg essential oil g(-1). At 0.950 aw, none of the essential oils had any significant effect on FB1 production. The results suggest that mainly cinnamon and oregano oils could be effective in controlling growth and FB1 production by F. proliferatum in maize under preharvest conditions.

Predicting mycotoxins in foods: a review.

The need to ensure the microbiological quality and safety of food products has stimulated interest in the use of mathematical models for quantifying and predicting microbial behaviour. For 20 years, predictive microbiology has been developed for predicting the occurrence of food-borne pathogens, although these tools are dedicated to bacteria. Recently, the situation has changed and a growing number of studies are available in the literature dealing with the predictive modelling approach of fungi. To our knowledge the present one is the first review focussed on predictive mycology and food safety, including mycotoxins; existing kinetic and probability models applied to mycotoxigenic fungi germination and growth, and mycotoxin production are reviewed.

Environmental factors, in vitro interactions, and niche overlap between Fusarium moniliforme, F. proliferatum, and F. graminearum, Aspergillus and Penicillium species from maize grain

The effects of temperature and water availability on growth and interactions between fumonisin-producing isolates of Fusarium moniliforme and F. proliferatum and seven other fungi from maize grain were determined in vitro . The type of interaction and index dominance ( I d ) between species were markedly influenced by temperature and a w . Generally, F. moniliforme and F. proliferatum were very competitive and dominant against the Penicillium spp. and A. flavus . They were in turn dominated by A. niger , but mutually antagonistic when paired with F. graminearum and A. ochraceus . Under slightly drier conditions ( a w ) A. ochraceus became more competitive and dominant over the fumonisin-producing species. A. flavus was dominant only at 30°C and a w . F. moniliforme and F. proliferatum demonstrated dominance against all species over a range of temperatures and 0.994 to 0.96 a w . At lower a w levels they were less competitive. The growth rate of the two fumonisin-producing species was significantly reduced by F. graminearum , regardless of a w . F. moniliforme and F. proliferatum reduced growth of Penicillium and Aspergillus spp., especially at > 0.96 a w . At a w , growth of these species was unaffected. Using Biolog plates the effect of a w and temperature on utilization patterns of carbon sources in maize were evaluated for the first time. The niche overlap indices relative to F. moniliforme and F. proliferatum were determined and compared with that of each interacting species. NOIs for F. moniliforme and F. proliferatum were > 0.90 at > 0.96 a w and 25 and 30°, indicative of co-existence with other species. Most of species had NOIs > 0.90, except in some cases when paired with F. moniliforme , where NOIs d and NOI methods both suggested that the niche overlap between species was in a state of flux and significantly influenced by both temperature and water availability. This suggests that interpretation of I d NOIs carried out under one set of environmental conditions may be misleading when considering interactions between species and also where screening for biocontrol potential is being considered.

Effect of water activity and temperature on growth and fumonisin B1 and B2 production by Fusarium proliferatum and F. moniliforme on maize grain

S. MARIN, V. SANCHIS, I. VINAS, R. CANELA AND N. MAGAN. 1995. The effect of different water activities (aw, 0.968, 0.956, 0.944, 0.925) and temperature (25°C and 30°C) on colonization and production of fumonisin B1 (FB1) and B2 (FB2) on sterile layers of maize by Fusarium proliferatum and F. moniliforme isolates was determined over periods of 6 weeks. Generally, both F. moniliforme and F. proliferatum grew faster with increasing aw and best at 30°C. All three isolates produced more FB1 than FB2 regardless of aw or temperature. Very little FB1 and FB2 were produced at 0.925 aw, with maximum produced at 0.956 and 0.968 aw at both temperatures tested. Most FB1 and FB2 were produced by F. moniliforme (25N), followed by F. proliferatum isolates (73N and 131N). At all aw levels and both temperatures there was an increase in FB1 and FB2 concentration with time. Statistical analyses of aw, temperature, time, two‐ and three‐way interactions showed some significant differences between isolates and FB1 and FB2 production.

Fumonisin-producing strains of Fusarium: a review of their ecophysiology.

This review focuses on the fumonisin-producing Fusarium species and the ecophysiology of these species. The effects of environmental biotic and abiotic factors on germination, growth, and fumonisin B1 production by Fusarium verticillioides and Fusarium proliferatum have been investigated under laboratory, field, and storage conditions. An understanding of the factors involved in production of fumonisins is the first step in preventing accumulation of these toxins.

Occurrence of Ochratoxigenic Fungi and Ochratoxin A in Green Coffee from Different Origins

Fungal infection and ochratoxin A (OTA) contamination were determined in green coffee samples from different origins, in which OTA-producing fungi were also identified. About 72% of the beans analysed by direct plating presented fungal infection, including species of Aspergillus, Penicillium and Rhizopus. The genus Aspergillus was presented in more than 90% of infected coffee beans. Aspergillus ochraceus and Aspergillus section Nigri isolates represented 2.8 and 65.4%, respectively from the total number of isolates from the coffee beans. The capacity to produce OTA was determined in 260 isolates of A. section Nigri and 19 of A. ochraceus by the agar plug method, giving positive results for 6% of the A. section Nigri isolates and 16% of the A. ochraceus. OTA production was analysed by high performance liquid chromatography. OTA contamination of green coffee beans was analysed by enzyme immunoassay. OTA levels in all samples analysed were above the limit of detection (0.6 mg/kg), with a mean OTA concentration of 6.7 mg/kg.

Effect of water activity and temperature on growth and ochratoxin production by three strains of Aspergillus ochraceus on a barley extract medium and on barley grains

Aspergillus ochraceus Wilhelm is a widespread storage fungus that has been isolated from grains such as barley. The objective of this study was to determine the effects of water activity (a(w)), temperature, time and their interactions on (a) growth on a barley extract agar medium, (b) growth on barley grains and (c) ochratoxin production on barley grains by three strains of A. ochracieus. For the three A. ochreceus isolates examined (NRRL 3174, 3.113 and 3.38), optimal a(w) levels for growth on agar media were in the range 0.98-0.96, with temperature optima of 30 degrees C for two of the isolates and 25-30 degrees C for the other isolate. Growth was observed at 10 and 37 degrees C, but only at higher a(w) levels assayed. Two dimensional profiles were constructed for the range of a(w) and temperature conditions that allow growth of the three isolates. Maximum growth on barley grains was reached at 30 degrees C, at both a(w) levels assayed (0.96 and 0.98), with fungal growth rates in the 4-5 mm day(-1) range. Maximum amounts of ochratoxins were produced at the highest a(w) treatment (0.98 a(w)) and after a three-week incubation time at 25-30 degrees C. The range of ochratoxin concentrations varied considerably, from 1.7 to 12,949 ppm, depending on the a(w) and temperature interactions.

Fate of mycotoxins in cereals during extrusion cooking: A review

Extrusion cooking is one of the fastest growing food-processing operations in recent years due to several advantages over traditional methods. Apart from its main goal of improving the quality of intermediate and final processed products, it may incidentally also improve safety because of the potential to reduce mycotoxin levels in cereals. This review is focused on extrusion cooking and aims to give a general overview of its impact in reducing mycotoxin levels in cereals. Extrusion cooking generally decreases the mycotoxins levels at rates depending on different factors such as the type of extruder, the type of screw, the die configuration, the initial mycotoxin concentration, the barrel temperature, the screw speed, the moisture content of the raw material and the use of additives. Reductions of 100, 95 and 83% for fumonisins, aflatoxins and zearalenone, respectively, have been reported during extrusion cooking of cereals, while lower reductions were observed for deoxynivalenol, ochratoxin A and moniliformin, where maximum reductions did not exceed 55, 40 and 30%, respectively.

Review: Ochratoxin A (OTA) in Wines, Musts and Grape Juices: Occurrence, Regulations and Methods of Analysis:

This work gives a general overview of ochratoxin A (OTA) occurrence in wines and the methodology for OTA analysis. The results of more than two thousand samples taken from the literature have been taken into account to quite extensively describe the present situation of OTA contamination of wine. According to these data, OTA is much more commonly detected in red wines than in rosé and white wines, and OTA concentration is remarkably higher than in the latter ones. Thus OTA could be detected in 45% (median 34%) of white wine samples, whereas it was detected in 66% (median 66%) of rosé and 71% (median 90%) of red wine samples. When comparing the wines from Northern and Southern regions, the latter showed a higher contamination than those from the Northern area. It has been suggested that OTA accumulation could be due to fungi belonging to the genus Aspergillus in wines from Southern European countries because the crops are exposed to elevated temperatures, which favour growth of OTA-producing Aspergillus species over Penicillium. High performance liquid chromatography (HPLC) associated with fluorescence detection preceded by extraction of OTA using commercially available immunoaffinity columns (IAC) is currently the most applied method for OTA determination in wines.