Filamentous fungi producing ochratoxin a during cocoa processing in Cameroon

Surveillance of ochratoxin A in cocoa beans from cocoa-growing regions of Ghana

Cocoa is one of the agricultural commodities which is highly susceptible to mycotoxin contamination. During two crop/harvest seasons, the occurrence and distribution of ochratoxin A (OTA) in viable commercial cocoa beans were investigated. The cocoa bean samples were collected randomly from farmers across cocoa-growing regions of Ghana. OTA concentrations in the samples were determined by liquid chromatography-tandem mass spectrometry (LC-MS/MS) methods following purification on immunoaffinity solid phase column. The result showed that 21.7% of all samples analyzed were contaminated with OTA at concentrations ranging from 0.01 μg/kg to 12.36 μg/kg. The Western South region had the highest occurrence of OTA-positive samples at 32.5%, followed by the Western North region at 28.75%, the Eastern and Volta regions at 25% each, Brong Ahafo (16.25%), Central (15%) and the Ashanti region at 11.25%. However, 0.9% and 3.5% of the total OTA-positive samples exceeded the OTA maximum limits of 10 μg/kg for cocoa beans and 3 μg/kg for cocoa powder, set by the Brazilian National Health Surveillance Agency and the European Commission, respectively. During the Main and Light crop seasons, the highest concentrations of OTA were detected in the Western North region, reaching up to 12.36 μg/kg and 3.45 μg/kg, respectively. OTA concentrations between the cocoa-growing regions in the Main crop season were not significantly different (p > 0.05), however, the Light crop season indicated a significant difference (p < 0.05). There was a significant difference (p < 0.05) between the two crop seasons. The need for regular monitoring and careful adherence to agronomic strategies such as good agricultural practices (GAPs), recommended code of practices (COPs) and good manufacturing practices (GMPs) for the prevention and reduction of OTA throughout the cocoa value chain cannot be overemphasized.

Molecular identification of endophytes from maize roots and their biocontrol potential against toxigenic fungi of Nigerian maize

Plants benefit from plant-associated microorganisms, of which endophytes are of particular interest as they are transmitted from generation to generation. This study characterises endophytes from maize roots and determines their biocontrol potential against toxigenic fungi in Nigerian maize. Maize roots were collected from farms in Lafia, and stored grain samples were collected from the six Northern States of Nigeria, from which endophytes and toxigenic fungal strains were isolated. Molecular identification employing 16SrRNA/internal transcribed spacer (ITS) sequences for isolated fungal endophytes was carried out, and mycotoxins produced by fungi were determined by high-performance liquid chromatography analysis. Biocontrol activity of the endophytes was determined using the dual culture confrontation test. Aspergillus and Fusarium genera were the prevalent isolated fungal species. Eight fungal endophytes were identified of which Trichoderma harzianum, Dichotomopilus erectus and Burkholderia spp. were the isolates with biocontrol activities, while 12 Aspergillus spp. were found to produce varying amounts of ochratoxin A and aflatoxin B1, respectively. T. harzianum showed the best inhibition (74%), followed by D. erectus (50%) and Burkholderia spp. (48%). T. harzianum showed poor inhibition of Aspergillus flavus (B7) at 30%. However, results from the Pakdaman Biological Control Index showed that T. harzianum has the best antifungal biocontrol activity of the three endophytes. The study concludes that antifungal biocontrol agents can be sourced from endophytes to obtain indigenous control activities that can check mycotoxin contamination of food and livestock feed, as well as elucidate possible metabolites for agricultural and industrial applications, which will help improve plant performance, increase crop yield and sustainability.

Survey of knowledge, and attitudes to storage practices preempting the occurrence of filamentous fungi and mycotoxins in some Ghanaian staple foods and processed products

Mycotoxigenic fungi can infect and produce potent mycotoxins in foodstuffs prior to harvest, during harvest (field fungi), and in storage after harvest (storage fungi), which when ingested, can result in adverse health effects. This study was aimed at assessing the knowledge, attitudes, and practices adopted by the Ghanaian populace to help mitigate the occurrence of molds and mycotoxins in foods. A cross-sectional survey involving a structured questionnaire was conducted with 642 respondents from twelve regions of Ghana. Descriptive statistics and analyses of variance were calculated. Correct Classification Rate (CCR) was measured to assess the utility of a logistic regression model. The results of the study showed that the majority of 299 (46.6%) of the respondents were between the ages of 18-25. Age and educational level were related to knowledge about the occurrence of fungi and mycotoxins in foods (p < 0.05). More than half the respondents, 50% indicated that they knew of aflatoxins as a major mycotoxin present in food. Higher education directly influenced on the knowledge of mycotoxicosis and the management of stored food to present intoxication by fungal metabolites. 502 (32.9%) knew that consuming foods with toxins could cause stomach aches. The most commonly consumed food commodity despite the presence of visible growth of fungi was bread (35.3%). The average KAP score for knowledge showed that, out of 100%, there was adequate knowledge (63.8%) among the members of the Ghanaian populace. Favorable environmental conditions of high humidity (> 85% ERH) and temperature (> 28-32 °C) enhance the proliferation of fungi in most foods and the attendant production of mycotoxins such as aflatoxins, ochratoxins, and fumonisins are associated with several severe human and animal health conditions; mycotoxicosis was associated with high fever, pain, vomiting, suppression of immunity, cancer, etc. when these foods are consumed on regular basis for a prolonged length of time. Future examination of the food items used for the School Feeding Programme in Ghana will offer opportunities to examine the risks of feeding youth with fungal-contaminated food preparations from providers.

Effect of spontaneous fermentation location on the fingerprint of volatile compound precursors of cocoa and the sensory perceptions of the end-chocolate

Cocoa pod-opening delay and bean fermentation promote the organoleptic quality of chocolate. The present research investigated the changes in the volatile fingerprint of cocoa harvested at a traditional plantation. Cocoa beans extracted from 2-days pod-opening delay were simultaneously fermented for 5 days using container and then sun-dried to 7-8% moisture content at five different locations: Akoupé, San Pedro, Soubré, Djekanou and Daloa. The aromatic analysis were done on cocoa using the HS-SPME-GC/MS technique. Professional panelists evaluated the sensory perceptions of the chocolate. The results shows that cocoa fermented in both Daloa and Soubré regions were differentiated by 2,3-butanediol while those processed in other regions presented highest acetoin content. However, fermented cocoa from Soubré region exhibited most amount of 2,3-butanediol, diacetate A whereas 2,3,5,6-tetramethylpyrazine differentiated those from Daloa region. Sensory properties of chocolate were not linked to the aromatic compound precursors profile of beans. The fermentation performed in San Pédro region promote both the generation of more desirable aromatic compounds of cocoa and sensory attributes of the finished chocolate. The fermentation location generates a greater differentiation of the volatile fingerprint of cocoa and the sensory perceptions of the finished chocolate.

The Role of Fungi in the Cocoa Production Chain and the Challenge of Climate Change

Background: The role of fungi in cocoa crops is mainly associated with plant diseases and contamination of harvest with unwanted metabolites such as mycotoxins that can reach the final consumer. However, in recent years there has been interest in discovering other existing interactions in the environment that may be beneficial, such as antagonism, commensalism, and the production of specific enzymes, among others. Scope and approach: This review summarizes the different fungi species involved in cocoa production and the cocoa supply chain. In particular, it examines the presence of fungal species during cultivation, harvest, fermentation, drying, and storage, emphasizing the factors that possibly influence their prevalence in the different stages of production and the health risks associated with the production of mycotoxins in the light of recent literature. Key findings and conclusion: Fungi associated with the cocoa production chain have many different roles. They have evolved in a varied range of ecosystems in close association with plants and various habitats, affecting nearly all the cocoa chain steps. Reports of the isolation of 60 genera of fungi were found, of which only 19 were involved in several stages. Although endophytic fungi can help control some diseases caused by pathogenic fungi, climate change, with increased rain and temperatures, together with intensified exchanges, can favour most of these fungal infections, and the presence of highly aggressive new fungal genotypes increasing the concern of mycotoxin production. For this reason, mitigation strategies need to be determined to prevent the spread of disease-causing fungi and preserve beneficial ones.

Moulds and their secondary metabolites associated with the fermentation and storage of two cocoa bean hybrids in Nigeria

Fungi and mycotoxin contamination of cocoa beans during fermentation and storage may constitute a hazard in the cocoa value chain and risk to consumers of its products. In this study, fungal profile and secondary metabolite patterns in two cocoa bean hybrids, F and T series, during fermentation and storage were determined. Additionally, secondary metabolite production by the recovered fungi in the beans was examined in culture media. Fungal isolates spanned six genera and eight species: Aspergillus niger, A. tamarii, Paecilomyces variotii, Penicillium citrinum, Pseudopithomyces palmicola, Simplicillium sp., Talaromyces atroroseus and Talaromyces sp.. In both hybrids, Aspergilli (38%) dominated the other fungi while more than one half of all the fungal isolates were from the beans in storage. Among the diverse secondary metabolites produced in media by the isolates were uncommon compounds, e.g. aspulvinone E produced by A. niger, aspterric acid by P. variotii, scalusamid A and sydowinin A by P. citrinum, norlichexanthone and siccanol by Simplicillium, and fallacinol and orsellinic acid by Talaromyces. The strains of P. citrinum produced up to 372 mg/kg citrinin. Forty-four fungal metabolites were quantified in both bean hybrids across the various processing stages, with about 86% occurring in the fermented beans stored for 30 days. The nephrotoxic citrinin, which was not previously reported in cocoa beans worldwide, was the only mycotoxin found in the fermented beans at overall mean concentration of 368 μg/kg. Additionally, its metabolite, dihydrocitrinone, was detected in fermented and stored beans. Consumption of freshly fermented cocoa beans may result in citrinin exposure. Appropriate fungal and mycotoxin control measures are proposed.

The challenges and perspectives of the selection of starter cultures for fermented cocoa beans

Fermentation is an essential process step to develop precursor compounds for aroma and flavour characteristics of chocolate, as well as preventing germination of the cocoa bean. Despite the importance of the role of microorganisms during the chocolate production, to date, there are some discrepancies of the "cocobiota" community found during fermentation and the impact of starter culture in fermented cocoa beans. This review provides both a detailed overview of the starter cultures used in fermented cocoa beans and the microbial diversity involved during this process, and an in-depth discussion of the methods used to identify these microorganisms. In this review, we included only published articles from 2008 to 2018 in English language. A total of forty-seven studies contributed to the description of the cocobiota from 13 different countries. In detail, we observed that the most common fermentation method used is the wooden box, followed by heap. Interestingly, 37% of the studies cited in this review did not mention the type of cocoa variety studied. Most of the techniques used to identify the microbiota are fingerprinting based (DGGE); however, few studies have been using next-generation technologies to elucidate the possible functions and interactions among microbes. Our results showed a greater diversity of yeasts if compared with bacterial involved in the fermentation. This review will help researchers seeking to design starter cultures to drive cocoa bean fermentation, and thus achieve a homogenous mass of fermented cocoa beans as well as serve as a guide for assessing methodologies for the identification of microorganisms.

Effects of environmental conditions and substrate on growth and ochratoxin A production by Penicillium verrucosum and Penicillium nordicum: Relative risk assessment of OTA in dry-cured meat products

Ecological conditions during ripening of dry-cured meat products favour the growth of an uncontrolled mould population that could suppose a risk of ochratoxin A (OTA) production. In this work the influence of water activity (a_w), temperature and substrate composition on fungal growth and OTA production by Penicillium nordicum and Penicillium verrucosum isolated from dry-cured meat products have been studied. In addition, the relative risk of OTA presence on dry-cured meat products has been evaluated using the Risk Ranger software. Fungal growth was observed in the range of 0.99-0.90 a_w and 15-25 °C being mainly temperature-dependent. P. nordicum and P. verrucosum were able to produce OTA in every substrate in these ranges of a_w and temperature. The production of OTA by P. verrucosum was mainly influenced by temperature and media composition. However, P. nordicum it is affected mainly by substrate or temperature depending on the strain studied. Both species produce a large amount of OTA on dry-cured ham and on dry-cured fermented sausage "salchichón" in environmental conditions usually found throughout the ripening of these products. The Risk Ranger software reveals that the relative risk of OTA on dry-cured meat products is 75%. Thus, control measures during dry-cured meat products processing to prevent OTA risk should be established.

Determination of potentially mycotoxigenic fungi in coffee (Coffea arabica L.) from Nayarit

A total of fourteen roasted coffee samples were collected from different local markets in Nayarit, Mexico. Twenty-two fungi isolates were related to the genera Aspergillus (54.54%) and Penicillium (4.5%). The strains R16 (0.33 μg/kg), 6N (1.16 μg/kg) and 11 (0.36 μg/kg) tested positive for OTA (ochratoxin A) production in PDA, the other fungi samples were not toxigenic. According to the sequence analysis of their ITS1-5.8S-ITS2 rDNA region, fungi OTA producers correspond to A. niger, A. versicolor and Byssochlamys spectabilis. These three strains were able to produce OTA when inoculated in roasted coffee in concentrations ranging from 75 to 90 μg/kg, after 21 days. Different production stages of roasted coffee (crop management, postharvest practices and storage) along with environmental conditions do not ensure mycotoxigenic fungi free products. This is the first report of OTA natural occurrence in roasted coffee from Nayarit.

Modified mycotoxins: An updated review on their formation, detection, occurrence, and toxic effects

Modified mycotoxins are metabolites that normally remain undetected during the testing for parent mycotoxin. These modified forms of mycotoxins can be produced by fungi or generated as part of the defense mechanism of the infected plant. In some cases, they are formed during food processing. The various processing steps greatly affect mycotoxin levels present in the final product (free and modified), although the results are still controversial regarding the increase or reduction of these levels, being strongly related to the type of process and the composition of the food in question. Evidence exists that some modified mycotoxins can be converted into the parent mycotoxin during digestion in humans and animals, potentially leading to adverse health effects. Some of these formed compounds can be even more toxic, in case they have higher bioaccessibility and bioavailability than the parent mycotoxin. The modified mycotoxins can occur simultaneously with the free mycotoxin, and, in some cases, the concentration of modified mycotoxins may exceed the level of free mycotoxin in processed foods. Even though toxicological data are scarce, the possibility of modified mycotoxin conversion to its free form may result in a potential risk to human and animal health. This review aims to update information on the formation, detection, occurrence, and toxic effects caused by modified mycotoxin.

Cocoa agronomy, quality, nutritional, and health aspects

The history of cocoa and chocolate including the birth and the expansion of the chocolate industry was described. Recent developments in the industry and cocoa economy were briefly depicted. An overview of the classification of cacao as well as studies on phenotypic and genetic diversity was presented. Cocoa agronomic practices including traditional and modern propagation techniques were reviewed. Nutrition-related health benefits derived from cocoa consumption were listed and widely reviewed. The specific action of cocoa antioxidants was compared to those of teas and wines. Effects of adding milk to chocolate and chocolate drinks versus bioavailability of cocoa polyphenols were discussed. Finally, flavor, sensory, microbiological, and toxicological aspects of cocoa consumption were presented.

Effect of post-harvest treatments on the occurrence of ochratoxin A in raw cocoa beans

Cocoa beans are the principal raw material for chocolate manufacture. Moulds have an important place in the change in the quality of cocoa beans due to their role in the production of free fatty acids and mycotoxins, namely ochratoxin A (OTA). This study investigated the impact of the key post-harvest treatments, namely the fermentation and drying methods on OTA contamination of raw cocoa beans. Analytical methods for OTA detection were based on solid-liquid extraction, clean-up using an immunoaffinity column, and identification by reversed-phase HPLC with fluorescence detection. Of a total of 104 randomly selected cocoa samples analysed, 32% had OTA contents above 2 µg kg(-1). Cocoa sourced from pods in a bad state of health had a maximum OTA content of 39.2 µg kg(-1), while that obtained from healthy pods recorded 11.2 µg kg(-1). The production of OTA in cocoa beans increased according to the pod-opening delay and reached 39.2 µg kg(-1) after an opening delay of 7 days after harvest, while 6.1 and 11.2 µg kg(-1) were observed when pods were opened after 0 and 4 days. OTA production also seemed to depend considerably to the cocoa fermentation materials. When using plastic boxes for bean fermentation, the OTA production was enhanced and reached an average OTA content of about 4.9 µg kg(-1), while the raw cocoa treated in banana leaves and wooden boxes recorded 1.6 and 2.2 µg kg(-1) on average respectively. In parallel, the OTA production was not really influenced by either the mixing or the duration of the fermentation or the drying materials.

Fungi and mycotoxins in cocoa: from farm to chocolate

Cocoa is an important crop, as it is the raw material from which chocolate is manufactured. It is grown mainly in West Africa although significant quantities also come from Asia and Central and South America. Primary processing is carried out on the farm, and the flavour of chocolate starts to develop at that time. Freshly harvested pods are opened, the beans, piled in heaps or wooden boxes, are fermented naturally by yeasts and bacteria, then dried in the sun on wooden platforms or sometimes on cement or on the ground, where a gradual reduction in moisture content inhibits microbial growth. Beans are then bagged and marketed. In processing plants, the dried fermented beans are roasted, shelled and ground, then two distinct processes are used, to produce powdered cocoa or chocolate. Filamentous fungi may contaminate many stages in cocoa processing, and poor practices may have a strong influence on the quality of the beans. Apart from causing spoilage, filamentous fungi may also produce aflatoxins and ochratoxin A. This review deals with the growth of fungal species and formation of mycotoxins during the various steps in cocoa processing, as well as reduction of these contaminants by good processing practices. Methodologies for fungal and mycotoxin detection and quantification are discussed while current data about dietary exposure and regulation are also presented.

Influence of fermentation and drying materials on the contamination of cocoa beans by ochratoxin A

Ochratoxin A (OTA) is a mycotoxin produced mainly by species of Aspergillus and Penicillium. Contamination of food with OTA is a major consumer health hazard. In Côte d’Ivoire, preventing OTA contamination has been the subject of extensive study. The current study was conducted to evaluate the influence of fermentation and drying materials on the OTA content in cocoa. For each test, 7000 intact cocoa pods were collected, split open to remove the beans, fermented using 1 of 3 different materials, sun-dried on 1 of 3 different platform types and stored for 30 days. A total of 22 samples were collected at each stage of post-harvesting operations. The OTA content in the extracted samples was then quantified by high-performance liquid chromatography. OTA was detected in beans at all stages of post-harvesting operations at varying levels: pod-opening (0.025 ± 0.02 mg/kg), fermentation (0.275 ± 0.2 mg/kg), drying (0.569 ± 0.015 mg/kg), and storage (0.558 ± 0.04 mg/kg). No significant relationships between the detected OTA level and the materials used in the fermentation and drying of cocoa were observed.

Producers and important dietary sources of ochratoxin A and citrinin

Ochratoxin A (OTA) is a very important mycotoxin, and its research is focused right now on the new findings of OTA, like being a complete carcinogen, information about OTA producers and new exposure sources of OTA. Citrinin (CIT) is another important mycotoxin, too, and its research turns towards nephrotoxicity. Both additive and synergistic effects have been described in combination with OTA. OTA is produced in foodstuffs by Aspergillus Section Circumdati (Aspergillus ochraceus, A. westerdijkiae, A. steynii) and Aspergillus Section Nigri (Aspergillus carbonarius, A. foetidus, A. lacticoffeatus, A. niger, A. sclerotioniger, A. tubingensis), mostly in subtropical and tropical areas. OTA is produced in foodstuffs by Penicillium verrucosum and P. nordicum, notably in temperate and colder zones. CIT is produced in foodstuffs by Monascus species (Monascus purpureus, M. ruber) and Penicillium species (Penicillium citrinum, P. expansum, P. radicicola, P. verrucosum). OTA was frequently found in foodstuffs of both plant origin (e.g., cereal products, coffee, vegetable, liquorice, raisins, wine) and animal origin (e.g., pork/poultry). CIT was also found in foodstuffs of vegetable origin (e.g., cereals, pomaceous fruits, black olive, roasted nuts, spices), food supplements based on rice fermented with red microfungi Monascus purpureus and in foodstuffs of animal origin (e.g., cheese).

Analysis of cocoa products for ochratoxin A and aflatoxins

Eighty-five samples of cocoa products sampled in Canada were analysed for ochratoxin A (OTA) and aflatoxins in 2011–2012. Inclusion of the aflatoxins in this survey required additional method development. Chocolate was extracted with methanol–water plus NaCl, while for cocoa two successive extractions with methanol and methanol–water were made. Extracts were cleaned on an AflaOchra immunoaffinity column (IAC). Determination was by reversed phase high performance liquid chromatography (HPLC). Detection of the aflatoxins was with a post-column photochemical reactor and of OTA by fluorescence detection. Mean limits of quantification (LOQ) of chocolate and cocoa powders were 0.16 ng/g (OTA) and 0.07 ng/g (aflatoxin B₁), respectively. Survey results showed that the incidences of OTA above the LOQ in natural cocoa were 15/15 (mean 1.17 ng/g), 20/21 for alkalized cocoa (mean 1.06 ng/g), 9/9 for baking chocolate (mean 0.49 ng/g), 20/20 for dark chocolate (mean 0.39 ng/g), 7/10 for milk chocolate (mean 0.19 ng/g), 5/5 for cocoa liquor (mean 0.43 ng/g), and 0/5 for cocoa butter. These results confirm our previous work with OTA. In the same samples, incidences of aflatoxin B₁ above the LOQ were 14/15 for natural cocoa (mean 0.86 ng/g), 20/21 for alkalized cocoa (mean 0.37 ng/g), 7/9 for baking chocolate (mean 0.22 ng/g), 16/20 for dark chocolate (mean 0.19 ng/g), 7/10 for milk chocolate (mean 0.09 ng/g), 4/5 for cocoa liquor (mean 0.43 ng/g), and 0/5 for cocoa butter. Both aflatoxins and OTA were confirmed by HPLC-MS/MS when OTA or aflatoxin levels found were above 2 ng/g in cocoa.

Masked mycotoxins: a review

The aim of this review is to give a comprehensive overview of the current knowledge on plant metabolites of mycotoxins, also called masked mycotoxins. Mycotoxins are secondary fungal metabolites, toxic to human and animals. Toxigenic fungi often grow on edible plants, thus contaminating food and feed. Plants, as living organisms, can alter the chemical structure of mycotoxins as part of their defence against xenobiotics. The extractable conjugated or non-extractable bound mycotoxins formed remain present in the plant tissue but are currently neither routinely screened for in food nor regulated by legislation, thus they may be considered masked. Fusarium mycotoxins (deoxynivalenol, zearalenone, fumonisins, nivalenol, fusarenon-X, T-2 toxin, HT-2 toxin, fusaric acid) are prone to metabolisation or binding by plants, but transformation of other mycotoxins by plants (ochratoxin A, patulin, destruxins) has also been described. Toxicological data are scarce, but several studies highlight the potential threat to consumer safety from these substances. In particular, the possible hydrolysis of masked mycotoxins back to their toxic parents during mammalian digestion raises concerns. Dedicated chapters of this article address plant metabolism as well as the occurrence of masked mycotoxins in food, analytical aspects for their determination, toxicology and their impact on stakeholders.

Antimicrobial activities of polyhexamethylene guanidine hydrochloride-based disinfectant against fungi isolated from cocoa beans and reference strains of bacteria

This study was conducted to assess the antibacterial and the antifungal activity of a polyhexamethylene guanidine hydrochloride (PHMGH)-based disinfectant and to determine if it could be used as a disinfectant for the treatment of cocoa beans. The activity of PHMGH was tested in vitro for efficacy against five reference strains of pathogenic bacteria and six strains of fungi isolated from cocoa beans. All the strains tested were sensitive to the disinfectant. The MICs reported were between 0.01 and 1.9 mg/ml and equal to the MBC or minimum fungicidal concentration (MFC) regardless of the strains of those microorganisms. The bacteria were more sensitive to PHMGH than were the fungi. Enterobacter cloacae was the most sensitive bacterium with a MIC and MBC of 0.01 mg/ml, whereas the genus Aspergillus was the least susceptible of the microorganisms tested, with a MIC and MFC from 1.0 to 1.9 mg/ml. The time required for the activity of PHMGH varies from 2 min for Enterobacter cloacae to 12 min for Aspergillus tamarii and generally increases with the MBC or the MFC. Through this in vitro study, the PHMGH has been proved to be bactericidal and fungicidal on the strains studied. Hence, it could probably serve as a fungicidal disinfectant for the treatment of cocoa beans after harvesting.

The effect of cocoa fermentation and weak organic acids on growth and ochratoxin A production by Aspergillus species

The acidic characteristics of cocoa beans have influence on flavor development in chocolate. Cocoa cotyledons are not naturally acidic, the acidity comes from organic acids produced by the fermentative microorganisms which grow during the processing of cocoa. Different concentrations of these metabolites can be produced according to the fermentation practices adopted in the farms, which could affect the growth and ochratoxin A production by fungi. This work presents two independent experiments carried out to investigate the effect of some fermentation practices on ochratoxin A production by Aspergillus carbonarius in cocoa, and the effect of weak organic acids such as acetic, lactic and citric at different pH values on growth and ochratoxin A production by A. carbonarius and Aspergillus niger in culture media. A statistical difference (ρ<0.05) in the ochratoxin A level in the cured cocoa beans was observed in some fermentation practices adopted. The laboratorial studies demonstrate the influence of organic acids on fungal growth and ochratoxin A production, with differences according to the media pH and the organic acid present. Acetic acid was the most inhibitory acid against A. carbonarius and A. niger. From the point of view of food safety, considering the amount of ochratoxin A produced, fermentation practices should be conducted towards the enhancement of acetic acid, although lactic and citric acids also have an important role in lowering the pH to improve the toxicity of acetic acid.

The effects of different ecophysiological factors on ochratoxin A production

Mycotoxin biosynthesis is affected by peculiar agro-ecosystem dependent conditions. Accordingly, the correlation between mycotoxin contamination and environmental condition change scenarios should be carefully considered. This is because fungal colonization and mycotoxin contamination could critically impair the availability of food products, especially in poor countries. At any time, the agricultural products might become susceptible to fungal contamination and mycotoxin production in uncontrolled storage. From 2000 to 2010, many studies were carried out in the case of the effects of different parameters on ochratoxin A (OTA) production by fungi in order to avoid providing the appropriate conditions for producing OTA. Water activity (a(w)), temperature, type of species and the substrates were introduced as the most important in these articles. This paper reviews the major published articles regarding the different ecophysiological factors influencing on OTA production.

Aflatoxigenic fungi and aflatoxin in cocoa

This paper reports the occurrence of aflatoxigenic fungi and the presence of aflatoxins in 226 cocoa samples collected on Brazilian farms. The samples were taken at various stages of fermentation, drying and storage. A total of 819 potentially aflatoxigenic fungi were isolated using Dichloran 18% Glycerol agar after surface disinfection, and identified by standard techniques. The ability of the fungi to produce aflatoxins was determined using the agar plug technique and TLC. The presence of aflatoxins in cocoa samples was determined by HPLC using post-column derivatization with bromide after immunoaffinity column clean up. The aflatoxigenic fungi isolated were Aspergillus flavus, A. parasiticus and A. nomius. A considerable increase in numbers of these species was observed during drying and storage. In spite of the high prevalence of aflatoxigenic fungi, only low levels of aflatoxin were found in the cocoa samples, suggesting the existence of limiting factors to the accumulation of aflatoxins in the beans.

Influence of post-harvest processing on ochratoxin A content in cocoa and on consumer exposure in Cameroon

Ochratoxin A (OTA) is a mycotoxin that contaminates several foodstuffs, including cocoa. It has nephrotoxic, teratogenic and carcinogenic properties in humans. The effect of post-harvest processing and storage on the OTA contamination of cocoa was studied over three successive cocoa seasons (2005, 2006 and 2007) in Cameroon. The type of fermentation (box or heap) did not significantly influence bean OTA content, which varied from undetectable (<0.03 ng/g) to 0.25 ng/g, remaining below 2 ng/g (the defined standard for cocoa beans). However, pod damage and late pod opening were aggravating factors for OTA contamination of cocoa. If pods were not intact (intentionally or naturally damaged), OTA was found in samples with contents of up to 75.5 ng/g before processing and 32.2 ng/g after 4 months' storage. This contamination exceeded the levels tolerated for export. In addition, some of the cocoa produced is processed locally and consumed as chocolate, cocoa powder, chocolate filled sweets, cocoa-based drinks and cocoa butter. In Cameroon, the average daily consumption of cocoa by-products is estimated at 0.75 g/d for adults and 1 g/d for children. Consequently, for maximum OTA contamination of cocoa beans, the maximum daily exposure to OTA would be 1.61 ng/kg bw/d in young children weighing around 20 kg, greatly contributing to the exposure of young consumers.

OTA-producing fungi isolated from stored cocoa beans

AIMS

The aim of this study was to identify fungal populations in unroasted cocoa beans stored in Spain in order to evaluate the ochratoxin A (OTA)-production ability of certain Aspergillus isolates.

METHODS AND RESULTS

Twenty batches of cocoa beans from different origins and with different OTA content were selected for this study. Three Aspergillus carbonarius and 13 Aspergillus niger aggregate strains isolated from these cocoa bean samples were selected to evaluate their OTA synthesis ability, being the only A. carbonarius isolates which are OTA producers [<limit of detection (LOD) = 3520 microg kg(-1) culture medium; LOD = 6 microg kg(-1) culture medium].

CONCLUSIONS

No correspondence was found between the OTA levels in cocoa beans and the presence of OTA-producing fungi. Nonetheless, some samples contained A. carbonarius with a high OTA-producing ability and, consequently, specific fungal controls should be set up during storage to avoid this toxin.

SIGNIFICANCE AND IMPACT OF THE STUDY

Toxigenic fungi in cocoa beans are not well understood. This study attempted to identify these fungi and evaluate their OTA-producing ability.

Ochratoxin A production by Aspergillus westerdijkiae in orange fruit and juice

To evaluate the incidence of fungi producing ochratoxin A in orange fruit and juice a survey was carried out by challenge test with ochratoxin A producing strains of Aspergillus westerdijkiae used as the model system. A. westerdijkiae grew into experimental lesions caused on orange surfaces, in orange natural medium and in orange juice and produced OTA in all environments. The higher temperature of 26 degrees C had a greater influence than temperatures of 20 degrees C and 4 degrees C on the growth of the mould, and OTA production. The environmental temperature of 20 degrees C, slows down but does not prevent toxin production. At the lowest temperature of 4 degrees C no growth was observed.