Reduction of ochratoxin A in extruded barley meal

The objective of this work was to determine the effects of extrusion cooking on the stability of ochratoxin A (OTA) in an artificially contaminated hulled barley meal (0.73-mm grain diameter) using a single screw extruder. The extrusion cooking parameters were temperature (140, 160, and 180 degrees C), initial moisture content of barley meal (24, 27 and 30%), and residence time (30, 40, 50, 60, and 70 s). Both unextruded and extruded samples were analyzed for OTA by high-performance liquid chromatography. Extrusion cooking variables significantly affected the stability of OTA (P < 0.05). Greater OTA reductions were achieved at higher residence time (70 s), medium temperature level (160 degrees C), and either high (30%) or low moisture (24%) content of samples. The amount of OTA destroyed during the extrusion process ranged from 17 to 86% depending on the studied parameters. The decrease in the amount of OTA after extrusion cooking followed first-order kinetics, showing that the fastest treatment in OTA reduction was that at 140 degrees C and 24% of moisture content.     

Ochratoxin A content in baby food

The purpose of this study was to investigate the ochratoxin A content in baby food. The analysis of ochratoxin A were performed by immunoaffinity column clean-up and HPLC with fluorescence detection. The detection limit was 0.2 mg/kg. Ochratoxin A was detected in 22.5% of 40 samples up to 1.2 mg/kg. Mean level was 0.15 and 0.31 mg/kg. Ochratoxin A level was higher in oat-based samples. Calculations made on the basis of the obtained means showed that the daily ochratoxin A dietary intake were up to 1.72 ng/kg b.w.     

Surveillance of stored grain from the 1997 harvest in the United Kingdom for ochratoxin A

This survey examined 306 samples of farm-stored wheat, barley and oats as received at, or tested by, central grain depots in the UK. Samples were taken from lorries or from stored grain using the existing inhouse procedures used for quality checking and examined for ochratoxin A using a fully validated analytical HPLC method with a detection limit of 0.1 μg/kg. Ochratoxin A was detected in 21 % of the samples examined, with barley more frequently contaminated than wheat. Mean concentrations of ochratoxin A found for all samples were 0.69 μg/kg in barley, 0.29 μg/kg in wheat and 0.15 μg/kg in oats. The highest concentration found was 17.8 μg/kg in a barley feed although concentrations of 81 and 30 μg/kg were found in 'reject-grade' wheat samples whose results were excluded from the main survey. In summary, 2.7 and 0.3 % of samples exceeded concentrations of 5 and 10 μg/kg respectively. There appeared to be significant relationships between ochratoxin A concentrations and moisture content, storage time and geographical area. Although conditions at harvest in 1997 were quite variable countrywide and often wet, results were similar to those found in earlier surveys carried out in the UK.     

Degradation of ochratoxin A and other mycotoxins by Rhizopus isolates

Several filamentous fungi representing the genera Rhizopus and Mucor were examined for their ability to degrade ochratoxin A (OTA), aflatoxin B1, zearalenone and patulin in a liquid medium. While none of the isolates exhibited aflatoxin degrading activity, ochratoxin A, zearalenone and patulin were decomposed by several isolates. Ochratoxin A was successfully degraded by Rhizopus stolonifer, R. microsporus, R. homothallicus and two R. oryzae isolates, and by four unidentified Rhizopus isolates. Kinetics of ochratoxin A detoxification of selected Rhizopus isolates was also examined. Rhizopus isolates were able to degrade more than 95% of ochratoxin A within 16 days. A R. stolonifer isolate could also effectively decompose ochratoxin A on moistened wheat. Further studies are in progress to identify the enzymes and genes responsible for ochratoxin detoxification and to transfer these genes to other Rhizopus isolates or microbes which could be used safely for decontamination of cereal products.     

Mycotoxin production in amber durum wheat stored at 15 and 19% moisture content

Ochratoxin A and citrinin developed in 11 kg parcels of amber durum wheat at 15% and 19% initial moisture content (MC) exposed to simulated bulk storage in a Manitoba granary for 60 weeks between July 1984 and September 1985. Other biotic and abiotic variables were monitored throughout the storage period. Ochratoxin A reached maximum levels of 11.8 and 0.11 ppm at 19 and 15% initial MC, respectively, during weeks 44-48; citrinin reached levels of 80.0 and 0.65 ppm at these respective moistures during the same period. The effect of 19% initial MC was significantly greater for the following variables: ochratoxin A, citrinin, Aspergillus flavus, Aspergillus glaucus group species, Alternaria species, Aspergillus versicolor, bacteria, fungal propagule count, seed germination, O2, CO2, moisture content, and fat acidity. Principal component analysis indicated that the first two components, describing greater than 60% of the variability in the data, partially defined the ecological relationships leading to mycotoxin production in the stored durum wheat system.     

Influence of harvesting and drying techniques on microflora and mycotoxin contamination of figs

Mould growth and mycotoxin (aflatoxins and ochratoxin A) formation were examined in the 1993 dried figs crop. The relationships between mould/mycotoxin contamination and orchard conditions, different harvesting techniques, harvesting time and intactness of fruits were investigated. The fruits were examined during drying and effects of different pretreatments, sun drying and solar drying on the mould and mycotoxin contamination in figs were also studied. Aflatoxins (B₁, B₂, G₁ and G₂) were not present in the firm or shrivelled ripe figs. Among the samples examined during drying, only one of the 32 samples was found to be aflatoxin positive. Ochratoxin A was not detected in any of the samples analysed. The moisture content, a_w and pH values of full ripe and shrivelled fruits were suitable for mould growth and mycotoxin formation while these parameters in pretreated and dried fruits were found to be too low to allow such outcome. It was observed that harvesting the fruit by hand-treating with different solutions and application of solar drying were effective in reducing contamination level.     

Ochratoxin A content in blood

The purpose of this study was to investigate the ochratoxin A content in blood plasma. The analysis of ochratoxin A were performed by immunoaffinity column clean-up and HPLC with fluorescence detection. The detection limit was 0.05 microg/l. Ochratoxin A was detected in all of 50 plasma samples up to 7.44 microg/l. Mean level was 1.54 microg/l. Ochratoxin A level was higher in men than in women and in August than in December. Calculations made on the basis of the obtained mean showed that the daily ochratoxin A dietary intake awere 3.03 ng/kg b.w.     

A simple chemical method reduces ochratoxin A in contaminated cocoa shells

Ochratoxin A (OTA) is a mycotoxin produced by Aspergillus and Penicillium species, which contaminates cocoa among other food commodities. It has been previously demonstrated that the toxin is concentrated in cocoa shells. The aim of this study was to assay a simple chemical method for ochratoxin A reduction from naturally contaminated cocoa shells. In order to determine the efficiency of the method, a high-performance liquid chromatography method with fluorescence detection was set up beforehand and validated. Ochratoxin A was extracted from cocoa shells with methanol-3% sodium bicarbonate solution and then purified with immunoaffinity columns. The recovery attained was 88.7% (relative standard deviation = 6.36%) and the limits of detection and quantification were 0.06 and 0.2 kg/kg, respectively. For decontamination experiments, the solvent extractor ASE 200 was used. First, aqueous solutions of 2% sodium bicarbonate and potassium carbonate were compared under the same conditions (1,500 lb/in2 at 40 degrees C for 10 min). Higher ochratoxin A reduction was obtained with potassium carbonate (83 versus 27%). Then, this salt was used under different conditions of pressure, temperature, and time. The greatest ochratoxin A reduction was achieved with an aqueous potassium carbonate solution (2%), at 1,000 lb/in2 at 90 degrees C for 10 min. This method could probably be applicable to the cocoa industry because it is fast and relatively economic. From the point of view of human health, the use of potassium carbonate, partially eliminated by rinsing the sample with water, does not likely represent a risk for human health.     

Studies on the sample weight for ochratoxin A determination in raw coffee

Ochratoxin A is a mycotoxin that may cause damage to the kidneys and the immune system in man. Foods are examined for this contaminant by the laboratories responsible for official food control. At present, there are no specific provisions for the sampling and examination of ochratoxin A in foods. Therefore, recourse is made to the provisions for aflatoxins. They prescribe the processing of samples with a weight of up to 30 kg. The examination of raw coffee for ochratoxin A in conjunction with the German Food Monitoring Programme of 2000 was undertaken with various sample weights (5, 10 and 30 kg) in order to identify the influence of the sample weight on the result. Overall, the sample weight did not have an effect on the detection and level of the ochratoxin A content in the samples of raw coffee examined.     

Occurrence of ochratoxin A in cocoa by-products and determination of its reduction during chocolate manufacture

This work reports an investigation carried out to assess the natural occurrence of ochratoxin A in 168 samples from different fractions obtained during the technological processing of cocoa (shell, nibs, liquor, butter, cake and cocoa powder) and the reduction of ochratoxin A during chocolate manufacture. Ochratoxin A analyses were performed with immunoaffinity columns and detection by high performance liquid chromatography. Concerning the natural ochratoxin A contamination in cocoa by-products, the highest levels of ochratoxin A were found in the shell, cocoa powder and cocoa cake. The cocoa butter was the least contaminated, showing that ochratoxin A seems to remain in the defatted cocoa solids. Under the technological conditions applied during the manufacture of chocolate in this study and the level of contamination present in the cocoa beans, this experiment demonstrated that 93.6% of ochratoxin A present in the beans was reduced during the chocolate producing.     

Mycotoxins in cereal grain. Part 12. Contamination with ochratoxin A and penicillic acid as indicator of improper storage of cereal grain

Formation of ochratoxin A and penicillic acid in wheat kernels at 6 moisture levels: 15, 18, 21, 24, 27 and 30% at 15 degrees C has been examined during 4 months of storage. The minimum time for formation of significant amount (0.5-1 mg/kg) of ochratoxin A and penicillic acid (6-8 mg/kg) in stored grain has been found for the various water contents as follows: 18%-16 weeks, 21%-6 weeks, 24% and more - 2 weeks. At 15% of moisture content formation of ochratoxin A and penicillic acid was not observed until 4 months of storage.     

玉米中赭曲霉毒素A 的辐照降解效果

目的：探讨γ射线对于玉米中赭曲霉毒素A的辐照降解效果。方法：以受赭曲霉毒素A污染的玉米为研究对象,采用高效液相色谱分析方法定量检测赭曲霉毒素A,比较不同剂量γ射线辐照处理的赭曲霉毒素A的降解率,评价辐照处理后玉米的营养组份。结果：玉米中赭曲霉毒素A经过辐照后,含量明显降低,在10kGy的辐照剂量下,降解率可达50%;经过辐照后玉米的营养组分没有明显变化。结论：辐照能够降解玉米中赭曲霉毒素A,且不会降低玉米品质。     

Mycotoxins in cereal grain Part 12. Contamination with ochratoxin A and penicillic acid as indicator of improper storage of cereal grain

Formation of ochratoxin A and penicillic acid in wheat kernels at 6 moisture levels: 15, 18, 21, 24, 27 and 30% at 15 °C has been examined during 4 months of storage. The minimum time for formation of significant amount (0.5–1 mg/kg) of ochratoxin A and penicillic acid (6–8 mg/kg) in stored grain has been found for the various water contents as follows: 18%–16 weeks, 21%–6 weeks, 24% and more — 2 weeks. At 15% of moisture content formation of ochratoxin A and penicillic acid was not observed until 4 months of storage.     

Ochratoxin degradation and adsorption caused by astaxanthin-producing yeasts

Ochratoxin degrading and adsorbing activities of Phaffia rhodozyma and Xanthophyllomyces dendrorhous isolates were tested. P. rhodozyma CBS 5905 degraded more than 90% of ochratoxin A (OTA) in 15 days at 20 degrees C. The data presented indicate that P. rhodozyma is able to convert OTA to ochratoxin alpha, and this conversion is possibly mediated by an enzyme related to carboxypeptidases. Chelating agents like EDTA and 1,10-phenanthroline inhibited OTA degradation caused by P. rhodozyma indicating that the carboxypeptidase is a metalloprotease, similarly to carboxypeptidase A. The temperature optimum of this enzyme was found to be above 30 degrees C, which is much higher than the temperature optimum for growth of P. rhodozyma cells, which is around 20 degrees C. The enzyme responsible for ochratoxin degradation was found to be cell-bound. Besides, both viable and heat-treated (dead) P. rhodozyma cells were also able to adsorb significant amounts (up to 250 ng ml(-1)) of OTA. Heat treatment enhanced OTA adsorbing activities of the cells. Further studies are in progress to identify the enzyme responsible for OTA degradation in P. rhodozyma.     

Analysis of Norwegian milk and infant formulas for ochratoxin A

Samples of organic cow's milk, conventional cow's milk, and cow's milk-based infant formulas were analysed for the occurrence of ochratoxin A by means of an HPLC method. The detection limit was 10ng/l. Ochratoxin A was detected in 6 out of 40 conventional cow's milk samples (range 11-58ng/l) , and in 5 out of 47 organic milk samples (range 15-28ng/l) . No ochratoxin A was detected in any of the 20 infant formula samples. The ochratoxin A levels in cow's milk found in this investigation are sufficient to cause a higher intake of ochratoxin A than the suggested TDI of 5ng/kg bw/ day, e.g. in small children who consume large quantities of milk.     

动物源性食品中赭曲霉毒素A污染概况及检测方法研究进展

赭曲霉毒素A(ochratoxin A,OTA)是一种由青霉属和曲霉属的真菌所产生的次级代谢产物,具有较强的肝毒性和肾毒性,并有致畸、致突变、致癌作用。赭曲霉毒素A极易造成饲料生产企业的饲料污染,这些产品被加工成为肉制品后,也会对人类造成危害。同时,不当的加工工艺和储存条件,还会造成香肠等肉制品受到赭曲霉毒素A污染。目前,国内缺少相关的国家标准检测方法,也没有动物源性食品中赭曲霉毒素A的判定依据,造成该领域的风险研究相对国外也比较匮乏。本文概述了动物源性食品赭曲霉毒素A污染状况,总结受污染的原因,介绍防控措施,并分析近年来针对不同类型动物源性食品的检测手段,以期为国内进行相关研究提供帮助。     

Effect of the frequency of the mixing of coffee cherries put out for drying on the kinetics of drying and the relationship to ochratoxin A production

The effect of the frequency of the mixing of coffee cherries put out for sun drying on the kinetics of the drying, fungal growth and kinetics of ochratoxin A production was evaluated. The results showed that the more coffee cherries were mixed, the quicker they dried. This rapidity of drying led to a reduction of fungal development. Indeed, coffee cherries mixed eight and ten times a day, dried quickly and were free inside of fungi. However, infection by fungi gives little indication of ochratoxin A production in coffee cherries. Indeed, although coffee cherries mixed twice a day were more contaminated by fungi, the analysis of ochratoxin A content showed they were free of this mycotoxin. The coffee cherries that were more contaminated by ochratoxin A were those mixed four times a day (containing 0.35-5.46 µg kg^-1 ochratoxin A). Ochratoxin A contamination was essentially due to the presence of Aspergillus species capable of producing ochratoxin A inside the coffee cherries.     

Optimization of process parameters for the production of an OTA-hydrolyzing enzyme from Aspergillus niger under solid-state fermentation

Ochratoxin A (OTA) is a mycotoxin found in several food and feed products. Due to its acute toxicity, innovative biological strategies to degrade OTA have been sought. In previous studies, Aspergillus niger MUM 03.58 was found to produce one promising OTA-hydrolyzing enzyme for food and feed applications. In this paper, we describe the optimization of a solid-state fermentation (SSF) process to produce this enzyme using the one-factor-at-a-time and the Taguchi experimental design approaches. A preliminary evaluation of the fermentation time, substrate moisture content and type of carbon source was done by the one-factor-at-a-time method. A final maximization of the OTA-hydrolyzing enzyme production was done using Taguchi's experimental design. An L9 orthogonal array was used to evaluate the effect of four factors at three levels. The substrate composition, the fermentation time, the operating temperature and the moisture content of the substrate were the factors evaluated. The results were tested by ANOVA and optimum conditions for a verification test were determined by statistical calculations. The optimized conditions were 30 g of wheat bran at 70% moisture incubated for 14 days at 25°C. A final productivity of 154 U/g substrate was achieved, which represents an approximately 3.7-fold increase in enzyme yield when compared with the starting point conditions.     

高效液相色谱法对谷物中赭曲霉毒素的测定

<正>霉菌遍布世界各地,种类繁多,依生活习性,分为仓储霉菌和田间霉菌。赭曲霉毒素是温暖地区最重要的仓储毒素,广泛存在于玉米、大麦、小麦和饲料中,麸皮的污染高于整粒谷物。在热带和亚热带地区主要由曲霉菌产生,而温暖地区则由青霉属产生。     

Ochratoxin A in conventional and organic cereal derivatives: a survey of the Italian market, 2001-02.

Ochratoxin A is a mycotoxin produced mainly by Penicillium verrucosum and Aspergillus ochraceus. Although typically considered a cereal contaminant, it has also been detected in dried fruit, nuts, meat and derivatives. To estimate the quantity of ochratoxin A that might be ingested by Italian consumers from these foods, 211 cereal derivatives (flours and bakery products) were analysed by high-performance liquid chromatography. Products were from conventional and organic agriculture and from integrated pest management agriculture. All commercial flours and derivatives examined contained ochratoxin A at concentrations very much below the legal limit (3 microg kg(-1)): the highest value, 0.816 microg kg(-1), was detected in a sample of spelt whole flour from organic agriculture. In many samples, the ochratoxin content was below the limit of detection; only rarely did values exceed 0.5 microg kg(-1). In baby foods, four samples were above the particularly restrictive Italian legal limit of 0.5 microg kg(-1). Although some significant differences were found between samples from conventional and organic agriculture when some product categories were examined (namely, baby foods as semolina and rice creams), no important difference was found between the two types of agricultural practice when all types of cereal derivatives were considered together.