Determination of ochratoxin A in regional samples of cow's milk from Germany

Detection, Contamination, Toxicity, and Prevention Methods of Ochratoxins: An Update Review

Ochratoxins (OTs) with nephrotoxic, immunosuppressive, teratogenic, and carcinogenic properties are thermostable fungal subordinate metabolites. OTs contamination can occur before or after harvesting, during the processing, packing, distribution, and storage of food. Mold development and mycotoxin contamination can occur in any crop or cereal that has not been stored properly for long periods of time and is subjected to high levels of humidity and temperature. Ochratoxin A (OTA) presents a significant health threat to creatures and individuals. There is also a concern of how human interaction with OTA will also express the remains of OTA from feedstuffs into animal-derived items. Numerous approaches have been studied for the reduction of the OTA content in agronomic products. These methods can be classified into two major classes: inhibition of OTA adulteration and decontamination or detoxification of food. A description of the various mycotoxins, the organism responsible for the development of mycotoxins, and their adverse effects are given. In the current paper, the incidence of OTA in various fodder and food materials is discussed, which is accompanied by a brief overview of the OTA mode of synthesis, physicochemical properties, toxic effects of various types of ochratoxins, and OTA decontamination adaptation methods. To our knowledge, we are the first to report on the structure of many naturally accessible OTAs and OTA metabolism. Finally, this paper seeks to be insightful and draw attention to dangerous OTA, which is too frequently neglected and overlooked in farm duplication from the list of discrepancy studies.

Occurrence of Ochratoxin A in Different Types of Cheese Offered for Sale in Italy

The detection of Ochratoxin A (OTA) in the milk of ruminants occurs infrequently and at low levels, but its occurrence may be higher in dairy products such as cheese. The aim of this study was to investigate the presence of OTA in cheeses purchased in the metropolitan city of Bologna (Italy) and the surrounding area. For the analysis, a LC-MS/MS method with a limit of quantification (LOQ) of 1 µg/kg was used. OTA was detected in seven out of 51 samples of grated hard cheese (concentration range 1.3-22.4 µg/kg), while it was not found in the 33 cheeses of other types which were also analysed. These data show a low risk of OTA contamination for almost all types of cheese analysed. To improve the safety of cheese marketed in grated form, more regulations on cheese rind, which is the part most susceptible to OTA-producing moulds, should be implemented or, alternatively, producers should consider not using the rind as row material for grated cheese. It would be interesting to continue these investigations particularly on grated hard cheeses to have more data to update the risk assessment of OTA in cheese, as also suggested by EFSA in its 2020 scientific opinion on OTA.

Immunochemical methods for ochratoxin A detection: a review

The safety of food and feed depends to a great deal on quality control. Numerous compounds and organisms may contaminate food and feed commodities and thus pose a health risk for consumers. The compound of interest in this review is ochratoxin A (OTA), a secondary metabolite of the fungi Aspergillus and Penicillium. Due to its adverse health effects, detection and quantification are of utmost importance. Quality control of food and feed requires extraction and analysis, including TLC, HPLC, MS, and immunochemical methods. Each of these methods has its advantages and disadvantages. However, with regard to costs and rapidity, immunochemical methods have gained much interest in the last decade. In this review an introduction to immunochemistry and assay design will be given to elucidate the principles. Further, the application of the various formats to the detection and quantification of ochratoxin will be described, including the use of commercially available kits.

Residue of ochratoxin a in chicken tissues-risk assessment

Background: Toxicological investigations of tissues of normally slaughtered chickens were carried out to provide preliminary evaluation of the incidence of OTA in chicken tissues (n=90). Majority of tissue samples were not found to contain measurable amounts of OTA, while in general, the OTA levels found in the analyzed tissue were low. Methods: The presence of OTA in tissue samples was determined by HPLC-FL after liquid-liquid extraction procedure. Method validation was performed according to the Commission Decision 2002/657/EC. Results: Of the 90 liver, kidney and gizzard samples originating from chicken farms located in the different agricultural areas of Serbia, OTA was reported in 23 (38.33%), 17 (28.3%) and 16 (26.6%) samples, respectively, with levels ranging from 0.14 to 3.9 ng/g in liver, 0.1 to 7.02 ng/g in kidneys and 0.25 to 9.94 ng/g in gizzard. None of the tissue samples contained more than the maximum level (10 ng/g) recommended by the European Commission. Conclusion: Low OTA results also suggested that chicken meat available in the retail market is unlikely to pose an adverse health risk to the consumers in respect to OTA toxicity.

Effects of ochratoxin a on livestock production

Ochratoxin A (OTA) contamination often causes large economic losses on livestock production. The intake of feed contaminated by OTA also represents a potential risk for animal health and a food safety issue due to the transfer of the toxin through the food chain to humans. The aim of this paper is to review the available literature on: (1) the frequency and degree of occurrence of OTA in different feedstuffs; (2) the toxicological effects of OTA intake on the performance of the main livestock (i.e., poultry, swine, cattle, goats and sheep); and (3) the transfer of OTA, or its metabolites, from animal feed into animal products such as milk, meat and eggs.

Ochratoxin a: general overview and actual molecular status

Ochratoxin A (OTA) is a mycotoxin produced by several species of Aspergillus and Penicillium fungi that structurally consists of a para-chlorophenolic group containing a dihydroisocoumarin moiety that is amide-linked to L-phenylalanine. OTA is detected worldwide in various food and feed sources. Studies show that this molecule can have several toxicological effects such as nephrotoxic, hepatotoxic, neurotoxic, teratogenic and immunotoxic. A role in the etiology of Balkan endemic nephropathy and its association to urinary tract tumors has been also proved. In this review, we will explore the general aspect of OTA: physico-chemical properties, toxicological profile, OTA producing fungi, contaminated food, regulation, legislation and analytical methods. Due to lack of sufficient information related to the molecular background, this paper will discuss in detail the recent advances in molecular biology of OTA biosynthesis, based on information and on new data about identification and characterization of ochratoxin biosynthetic genes in both Penicillium and Aspergillus species. This review will also cover the development of the molecular methods for the detection and quantification of OTA producing fungi in various foodstuffs.

Ochratoxin A in ruminants−A review on its degradation by gut microbes and effects on animals

Ruminants are much less sensitive to ochratoxin A (OTA) than non-ruminants. The ruminal microbes, with protozoa being a central group, degrade the mycotoxin extensively, with disappearance half lives of 0.6–3.8 h. However, in some studies OTA was detected systemically when using sensitive analytical methods, probably due to some rumen bypass at proportions of estimated 2–6.5% of dosage (maximum 10%). High concentrate proportions and high feeding levels are dietary factors promoting the likeliness of systemic occurrence due to factors like shifts in microbial population and higher contamination potential. Among risk scenarios for ruminants, chronic intoxication represents the most relevant.

Ochratoxin A in ruminants−A review on its degradation by gut microbes and effects on animals

Ruminants are much less sensitive to ochratoxin A (OTA) than non-ruminants. The ruminal microbes, with protozoa being a central group, degrade the mycotoxin extensively, with disappearance half lives of 0.6-3.8 h. However, in some studies OTA was detected systemically when using sensitive analytical methods, probably due to some rumen bypass at proportions of estimated 2-6.5% of dosage (maximum 10%). High concentrate proportions and high feeding levels are dietary factors promoting the likeliness of systemic occurrence due to factors like shifts in microbial population and higher contamination potential. Among risk scenarios for ruminants, chronic intoxication represents the most relevant.

Comparison of off- and in-line solid-phase extraction for enhancing sensitivity in capillary electrophoresis using ochratoxin as a model compound

This paper proposes and compares two approaches based on off- and in-line solid-phase extraction (SPE), intended to enhance sensitivity in capillary electrophoresis with ultraviolet detection (CE-UV) using as a model the determination of ochratoxin A (OA) in river water samples. In the off-line SPE mode, the reversed-phase sorbent (octadecilsylane, C(18)) selectively retains the target analyte (OA) and allows large volumes of the sample (70 mL) to be introduced and subsequently eluted in a small volume (0.1 mL) of an appropriate solution. In the in-line SPE mode, a custom-made microcartridge is inserted near the inlet of the capillary, which is filled with the same C(18) sorbent. This solid phase selectively retains OA present in a sample volume as low as approximately 640 microL for subsequent elution with ca. 135 nL of an appropriate eluent. The limit of detection (LOD) obtained with the in-line SPE method was 1 ng L(-1), which is 3 orders of magnitude lower than that obtained with CE-UV and roughly 1 order lower than that provided by the off-line SPE-CE-UV method.

Ochratoxin a: comparison of extraction methods from grapes and quantitative determination by different competitive enzyme-linked immunosorbent assay kits

The European Community has recently established a maximum limit for ochratoxin A (OTA) concentration in grapevine products, but many practical difficulties remain concerning the establishment of optimum cost-effective methods of quantification. The performance of four extraction procedures and three commercial competitive enzyme-linked immunosorbent assays (cELISAs) for grapes were compared. Results differed for the extractions and the cELISA kits. The advantage of using immunoaffinity columns (IACs) in the extraction was the excellent detection limit, which was between 0.06 and 0.0075 ng ml(-1) depending on the cELISA kit used. Despite lower sensitivity (between 1.2 and 0.15 ng ml(-1) depending on the cELISA kit), an extraction method in liquid phase, which was simple and inexpensive, was confirmed as suitable for quantifying OTA at levels estimated to be dangerous for human health. Two of the three cELISA kits produced satisfactory results. When these two cELISAs were coupled with IAC extraction, the lower quantification limits were 0.010 and 0.0075 ng ml(-1), respectively, and the dynamic ranges were 50 and 27, respectively. The most reliable procedures were then compared with the reference method, high-performance liquid chromatography plus fluorescent detection coupled with an IAC. The results were very similar, although the cELISAs generally provided slightly higher values than did the chromatography method. The IAC method coupled with the cELISA was four times more sensitive than was the IAC method coupled with the chromatography method. The cELISA detection techniques were excellent alternatives to the already established chromatographic protocols, especially for mass screening and for determining concentrations of OTA as low as 0.010 ng ml(-1).

Combined use of supported liquid membrane and solid-phase extraction to enhance selectivity and sensitivity in capillary electrophoresis for the determination of ochratoxin A in wine

This paper proposes a novel strategy to enhance selectivity and sensitivity in CE, using supported liquid membrane (SLM) and off-line SPE simultaneously. The determination of ochratoxin A (OA) in wine has been used to demonstrate the potential of this methodology. In the SLM step, the donor phase (either a 20 mL volume of a standard solution at pH 1 or a wine sample at pH 8) was placed in a vial, where a micromembrane extraction unit accommodating the acceptor phase (1 mL water, pH 11) in its lumen was immersed. The SLM was constructed by impregnating a porous Fluoropore Teflon (PTFE) membrane with a water-immiscible organic solvent (octanol). In the off-line SPE step, the nonpolar sorbent (C-18, 4 mg) selectively retained the target ochratoxin, enabling small volumes of acceptor phase (1 mL) to be introduced. The captured analytes were eluted in a small volume of methanol (0.1 mL). This procedure resulted in sample cleanup and concentration enhancement. The method was evaluated for accuracy and precision, and its RSD found to be 5%. The LODs for OA in the standard solutions and wine samples were 0.5 and 30 microg/L, respectively. The results obtained demonstrate that SLM combined with off-line is a good alternative to the use of immunoaffinity columns prior to CE analysis.

Aflatoxin M1 and ochratoxin A in raw bulk milk from French dairy herds

Mycotoxins in milk are a public health concern and have to be regularly monitored. A survey on the presence of aflatoxin M1 (AFM1) and ochratoxin A (OTA) in raw bulk milk was conducted in 2003 in the northwest of France, the main French milk-producing basin. Randomly selected farms (n = 132) were characterized by a diet based on corn silage and containing a large proportion of on-farm produced cereals, feeding sources that are frequently contaminated by mycotoxins. Farms were surveyed twice in winter and in summer. At each sampling time, a trained surveyor completed a questionnaire recording farm management procedures and production traits. The AFM1 was found in 3 out of 264 samples but at levels (26 ng/L or less) that are below the European legislation limit of 50 ng/L. Traces of AFM1 (less than 8 ng/L) were also found in 6 other samples. The OTA was detected in 3 samples also at low levels, 5 to 8 ng/L. Farms that tested positive to the presence of mycotoxins, 12 in total including 6 farms that had traces of AFM1, differed from negative farms by a more extensive use of total mixed rations, 58 vs. 27%. In addition, the positive farms tended to have lower milk yields. Although the incidence of milk contamination with AFM1 and OTA at the farm level was low during the period studied, production and management data from the surveyed farms suggest a link between feeding management practices and mycotoxin contamination.

Analysis of ochratoxin A in milk after direct immunoaffinity column clean-up by high-performance liquid chromatography with fluorescence detection

The present work describes a new analytical method for direct immunoaffinity column clean-up of ochratoxin A (OTA) in milk samples followed by determination of the toxin using high-performance liquid chromatography with fluorescence detection (HPLC-FD). Two different immunoaffinity cartridges (IAC) were investigated, and Ochraprep columns were chosen because they showed the best results. An average recovery of 89.8% and a mean RSD of 5.8% for artificially contaminated cow's milk in the range of 5-100 ng/L were attained. The calculated limit of detection (LOD) and limit of quantitation (LOQ) were as low as 0.5 and 5 ng/L, respectively. This new easy and fast method avoids a previous liquid-liquid extraction step and therefore the use of toxic chlorinated solvents. Chromatograms of the final extracts were clean and OTA could be easily detected at a retention time of 8.4 min without interferences. To assess the presence of the toxin in cow's milk eight samples of skimmed and four samples of whole milk were analysed and OTA was not detected over the established detection limit.

Determination of ochratoxin A in human urine by solid-phase microextraction coupled with liquid chromatography-fluorescence detection

A new method for the determination of ochratoxin A (OTA) in human urine samples has been developed using solid-phase microextraction (SPME) interfaced with liquid chromatography-fluorescence detection (LC-FD). This method is simpler and cheaper compared to the most widely adopted clean-up procedures for OTA extraction from urine (usually based on immunoaffinity columns). Briefly, urine samples, diluted 1:5 with phosphate buffer (10 mM, pH 3), were partitioned against chloroform and the aqueous phase extracted by a polydimethylsiloxane/divinylbenzene (PDMS/DVB) fiber. The fiber was then "statically" desorbed, through a SPME interface, into a LC system operating in isocratic conditions. The linear range investigated in urine was 0.01-1 ng/ml. Within-day R.S.D.% in urine spiked at 0.1 and 1 ng/ml were 3.9 and 1.9, respectively, whereas the between-days R.S.D.% were 5.5 and 3.0, respectively. The limits of detection (LOD) and quantitation (LOQ) calculated at a signal-to-noise ratio of 3 and 10 (noise calculated peak to peak on a blank chromatogram at the OTA retention time) were 0.01 and 0.05 ng/ml, respectively.

Preliminary study of Ochratoxin A in human plasma in agricultural zones of Chile and its relation to food consumption

Ochratoxin A (OTA) is a mycotoxin produced by different species of Aspergillus and Penicillium fungi. The presence of OTA in human blood has been reported in many studies, especially in Europe, however none have been done in South America. In this study, 88 blood samples from healthy donors from two different Chilean agricultural zones were analyzed. In parallel with sample collection, the donors filled a questionnaire regarding food intake during the last three months. The blood samples were collected in Colbún in March and July of 2004 and in San Vicente de Tagua--Tagua in October of 2004. The extraction procedure was done in the solid phase with a Sep-Pak RP-18 cartridge and a final purification with immunoaffinity Ochraprep columns. The presence of OTA was confirmed by the formation of Ochratoxin A methyl ester. Fifty four percent of the samples collected in Colbún and 91% of samples from San Vicente de Tagua - Tagua were positive to OTA at ranges of 0.07-2.75 ppb and 0.22-2.12 ppb, respectively. The OTA levels in serum did not show a good correlation with normal dietary consumption.

Two different clean-up procedures for liquid chromatographic determination of ochratoxin A in urine

This paper describes two different procedures for extraction of ochratoxin A (OTA) from urine samples: one using acidic chloroform-methanol mixture, followed by solid-phase extraction (SPE) clean-up and the other using commercial Chem Elut columns and a chloroform-formic acid mixture. The recovery of OTA using the procedure with silica gel columns was 82% with a R.S.D. < 8.4% and the detection and quantitation limits were 0.5 and 1.5 ng OTA/ml, respectively. The recovery of OTA in the second procedure with urine samples purified only on commercial Chem Elut columns was 95% with R.S.D. < 4.0%, and detection and quantitation limits 0.3 and 0.9 ng/ml, respectively. Both procedures of OTA extraction effectively eliminate interfering substances and give reliable and repeatable results. However, the procedure with Chem Elut columns gave higher recovery and lower detection and quantitation limits. It was successfully applied in determining OTA in human urine samples.

Analysis of ochratoxin A in foods consumed by inhabitants from an area with balkan endemic nephropathy: a 1 month follow-up study

In the 1950s, a series of publications from Bulgaria, Yugoslavia, and Romania locally described a kidney disease called Balkan Endemic Nephropathy (BEN). In Bulgaria, the exposure of populations to ochratoxin A (OTA) was supported by analysis of individual food items demonstrating a higher prevalence and higher levels of OTA in food from the high-incidence areas of BEN. In this work, food consumption from a series of individuals from two villages of the BEN area during 1 month was followed using the duplicate diet method. Meals consumed by volunteers from both villages showed uneven OTA contents, spreading from below the limit of quantification (<0.07 microg/kg) to 2.6 microg/kg. The average weekly intake of OTA varies from 1.86 to 92.7 ng/kg of body weight. Some of these levels approach the provisional tolerable weekly intake (PTWI) established by the JECFA at 100 ng/kg of body weight. These results confirm previous studies performed in the same area and demonstrate the high exposure of this population to OTA, thus strengthening the hypothesis of the involvement of this mycotoxin in BEN etiology.

Methods of analysis for ochratoxin A

The mycotoxin ochratoxin A (OTA) is produced by the fungi Aspergillus alutaceus and Penicillium verrucosum and has carcinogenic, nephrotoxic, teratogenic and immunosuppressive properties. The levels of OTA in foodstuffs are regulated in several countries, so reliable and sensitive methods are necessary for its determination. Procedures for extraction of OTA from ground foods generally use an organic solvent in the presence of acid or an extraction solvent containing aqueous sodium bicarbonate. Cleanup procedures include partition into aqueous sodium bicarbonate, solid phase extraction (SPE) columns and immunoaffinity chromatography. The latter technique allows detection of sub-ppb levels of OTA in a wide variety of foods and in plasma. The most widely used determinative procedure is reversed phase liquid chromatography (LC) with detection by fluorescence (excitation 330-340 nm, emission 460-470 nm) or, more recently, by tandem mass spectrometry. ELISA methods are also available. Certified reference materials containing OTA have been prepared.

Assessment of dietary exposure to ochratoxin A in the UK using a duplicate diet approach and analysis of urine and plasma samples

The approach to assess exposure to ochratoxin A from the diet by the analysis of human plasma and urine samples has been developed. Composite duplicate diet samples from 50 individuals and corresponding plasma and urine samples were obtained over 30 days. Samples were analysed using sensitive methods capable of measuring ochratoxin A at 0.001 ng g(-1) in food, 0.1 ng ml(-1) in plasma and 0.01 ng ml(-1) in urine. Analysis of the foods indicated ochratoxin A levels contributing to an average intake in the range 0.26-3.54 ng kg(-1) bw day(-1) over the 30 days. Ochratoxin A was found in all plasma samples and in 46 urine samples. The correlation between the plasma ochratoxin A levels and ochratoxin A consumption was not significant (95% confidence limit). However, a significant correlation was found between ochratoxin A consumption and the urine ochratoxin A concentration expressed as the total amount excreted. This new work offers the possibility of using ochratoxin A in urine as a simple and reliable biomarker to estimate exposure to this mycotoxin.

Determination of ochratoxin A in pig liver-derived pâtés by high-performance liquid chromatography

A solid phase extraction procedure followed by HPLC analysis with fluorescence detection has been developed for ochratoxin A (OTA) in pâtés derived from pig liver. After a previous extraction of OTA with 60% acetonitrile, all the samples were purified through C8 columns. The percentage recovery was 85.7% and the lower limits calculated for accurate detection and quantitation were 0.56 ng/g and 0.84 ng/g respectively. The HPLC procedure showed a good linearity in the interval of equivalent OTA concentrations of 0.84 to 3 ng/g. Values <10% were obtained for precision in HPLC determinations performed (n = 3) and (n = 9). Stability of calibration standards and samples during the analytical procedure was also demonstrated. This method was successfully applied to 38 pig-derived pâtés and three samples were found to be positive with OTA levels above the detection limit. The highest concentration (1.77 ng/g) has been found in a home-made pâté.

Solid-phase extraction applied to the determination of ochratoxin A in wines by reversed-phase high-performance liquid chromatography

A reversed-phase high-performance liquid chromatographic method is described for the analysis of Ochratoxin A at low microg l(-1) levels in samples of artificially contaminated wines. The method involves solid-phase extraction of samples using octadecylsilane cartridges and an additional preconcentration step prior to chromatography with isocratic elution and fluorimetric detection. The method was evaluated for accuracy and precision with relative standard deviations lower than 10%. Recoveries of ochratoxin A added to commercial wines over the range 0.1-3.0 microg l(-1) were higher than 80% in the assays. The performance of the octadecylsilane cartridge method tested compared very favourably with results of other published studies of ochratoxin A which use immunoaffinity columns or solvent extraction techniques.

Chromatographic methods for the determination of ochratoxin A in animal and human tissues and fluids

This paper gives a review of chromatographic methods used for the determination of ochratoxin A (OA) in animal and human tissues and fluids. These methods are needed for example for monitoring studies of OA occurrence in the food chain and for studies dealing with the OA carry-over. In this survey, emphasis was given to HPLC methods. The review includes sampling, sample storage, extraction, spiking procedures, clean-up, detection and determination, and confirmation procedures. Emphasis is laid on special problems associated with the analysis of animal tissues and fluids.