Antonio J. Ramos

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.

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.

Prevention of aflatoxicosis in farm animals by Means of hydrated sodium calcium aluminosilicate addition to feedstuffs: a review

Abstract Mycotoxins are a wide group of fungal toxins that have been associated with severe toxic effects in man and animals. Aflatoxins are the most dangerous of these fungal secondary metabolites. Because there is no definitive way in which complete detoxification of food and feed contaminated with mycotoxins can be achieved, new methods to eliminate mycotoxicosis are sought. Hydrated sodium calcium aluminosilicate (HSCAS), a sorbent compound obtained from natural zeolite, has demonstrated an ability to sorb mycotoxins with a high affinity. Addition of this compound to feedstuffs contaminated with aflatoxins has shown a protective effect against the development of aflatoxicosis in farm animals. Several authors have postulated that the main mechanism implicated in this process could be chemisorption of the toxins through the formation of a stable complex comprising HSCAS and the mycotoxins. This complex is not able to cross the luminal membrane of the gastrointestinal tract and therefore the bioavailability of aflatoxins is reduced in a dose-dependent manner. This review comments on the in vitro and in vivo application of HSCAS to sorb aflatoxins and other mycotoxins. The effect on animal performance of dietary addition of HSCAS to feedstuffs contaminated with mycotoxins is discussed in a variety of farm animals.

In vitro aflatoxin adsorption by means of a montmorillonite silicate. A study of adsorption isotherms

Abstract To evaluate the affinity and capacity of a feedstuff additive, a montmorillonite silicate, to adsorb the four major naturally occurring aflatoxins, a study of the Langmuir and Freundlich adsorption isotherms was carried out. The Freundlich isotherm fits the data better than the Langmuir isotherm. The data reveal adsorptions of about 1000 μg aflatoxin B 1 g −1 montmorillonite, 425–450 μg aflatoxin G 1 g −1 , 230 μg aflatoxin G 2 g −1 and 200 μg aflatoxin B 2 g −1 . The superior results obtained with the Freundlich isotherm suggest either the presence of a heterogeneous sorbent surface, or the co-existence of different adsorption mechanisms, or both phenomena at the same time, the saturation of the adsorbent material being far from complete.

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.

Survey: Ochratoxin A in European special wines

The occurrence of Ochratoxin A (OTA) was examined in 121 special wines made using different winemaking techniques and from many European origins. The wine groups with the highest OTA content and occurrence, above 90%, were those were the must was fortified before fermentation (mean: 4.48μg/l) and those made from grapes dried by means of sun exposure (mean: 2.77μg/l). Fortified wines with long aging in wooden casks were about 50% contaminated, with OTA levels below 1.00μg/l. Wines affected by noble rot, late harvest wines and ice wines did not contain OTA. Overall, 19.8% of the wines studied contained OTA levels above the maximum permissible limit for the European Union (2μg/kg) in wine (excluding liqueur wines).

VeA and LaeA transcriptional factors regulate ochratoxin A biosynthesis in Aspergillus carbonarius

Ochratoxin A (OTA) is a mycotoxin with nephrotoxic, teratogenic and immunotoxic properties which represents a serious risk for human and animal health. Aspergillus carbonarius is considered the main OTA-producing species in grapes and products such as raisins, wine or juices, although it has also been isolated from coffee, cocoa and cereals. Till now not much information is available about regulatory mechanisms of OTA production by A. carbonarius. A better understanding of how environmental factors influence OTA production and which genes are involved in its regulation could help us design new control strategies. In this study, we have evaluated the role of VeA and LaeA transcriptional factors, which have been shown to regulate secondary metabolism in response to light in A. carbonarius. To this aim, veA and laeA genes were deleted in an ochratoxigenic A. carbonarius strain by targeted gene replacement using Agrobacterium tumefaciens-mediated transformation. Loss of veA and laeA in A. carbonarius yields to an organism with slight differences in vegetative growth but a strong reduction in conidial production. A drastic decrease of OTA production that ranged from 68.5 to 99.4% in ΔveA and ΔlaeA null mutants was also observed, which was correlated with a downregulation of a nonribosomal peptide synthetase involved in OTA biosynthesis. These findings suggest that VeA and LaeA have an important role regulating conidiation and OTA biosynthesis in response to light in A. carbonarius in a similar way to other fungi where functions of VeA and LaeA have been previously described. This is the first report of a transcriptional factor governing the production of OTA by A. carbonarius.

In situ absorption of aflatoxins in rat small intestine

To evaluate the rate at which the four main aflatoxins (aflatoxins B1, B2, G1 and G2) are able to cross the luminal membrane of the rat small intestine, a study about intestinal absorption kinetics of these mycotoxins has been made. In situ results obtained showed that the absorption of aflatoxins in rat small intestine is a very fast process that follows first-order kinetics, with an absorption rate constant (ka) of 5.84±0.05 (aflatoxin B1), 4.06±0.09 (aflatoxin B2), 2.09±0.03 (aflatoxin G1) and 1.58±0.04 (aflatoxin G2) h−1, respectively.

Mycobiota and co-occurrence of mycotoxins in Capsicum powder

This study aimed to: (1) determine the mycobiota of Capsicum powder samples, paying a special attention to the mycotoxigenic moulds; (2) evaluate the contamination levels of aflatoxins (AF), ochratoxin A (OTA), zearalenone (ZEA), deoxynivalenol (DON), T2 and HT2 toxins in those samples. Thirty-two samples were obtained through the methods of sampling established by the European Union legislation. Aspergillus and Eurotium were the most frequently found genera. Aspergillus section Nigri had the higher relative frequency in the samples, A. niger aggregate being the most representative group of this section. Other potentially mycotoxigenic Aspergillus, Fusarium and Penicillium species were found, but in a lower frequency. Co-occurrence of mycotoxins was confirmed in the 32 Capsicum powder samples. All samples were contaminated with AF and OTA, 27% with ZEA (36% of chilli and 18% of paprika samples), 9% with DON (18% of chilli and 6% of paprika samples), 6% with T2 (18% of chilli samples) and none of the samples contained HT2. Although in the present study the most common genera found (Aspergillus and Eurotium) belong to storage moulds, some field fungi such as Fusarium spp. were also found, and their toxins were sometimes detected. This fact supports the hypothesis that mycotoxin contamination of Capsicum products may occur both in the field and/or during storage.

Modelling Aspergillus flavus growth and aflatoxins production in pistachio nuts.

Aflatoxins (AFs) are the main contaminants in pistachio nuts. AFs production in pistachio has been attributed to Aspergillus flavus. The aim of this study was to apply existing models to predict growth and AFs production by an A. flavus isolated from pistachios as a function of moisture content and storage temperature of pistachios in order to test their usefulness and complementarities. A full factorial design was used: the moisture content levels assayed were 10, 15, 20, 25 and 30% and incubation temperatures were 10, 15, 20, 25, 30, 37 and 42 °C. Both kinetic and probability models were built to predict growth of the strain under the assayed conditions. Among the assayed models, cardinal ones gave a good quality fit for radial growth rate data. Moreover, the progressive approach, which was developed based on a reduced number of experimental points led to an improved prediction in the validation step. This is quite significant as may allow for improved experimental designs, less costly than full factorial ones. Probability model proved to be concordant in 91% of the calibration set observations. Even though the validation set included conditions around the growth/no-growth interface, there was a 100% agreement in the predictions from the data set (n = 16, cut off = 0.5) after 60 days. Similarly, the probability for AF presence was rightly predicted in 89% of the cases. According to our results EC maximum aflatoxin levels would be surpassed in a period as short as 1 month if pistachio nuts reach 20 °C, unless %mc is ≤10%.