Mycobiota of cocoa: From farm to chocolate

Counts of mesophilic aerobic, mesophilic anaerobic, thermophilic aerobic sporeforming bacteria and persistence of Bacillus cereus spores throughout cocoa powder processing chain

Sporeforming bacteria are a concern in some food raw materials, such as cocoa powder. Samples (n = 618) were collected on two farms and at several stages during cocoa powder manufacture in three commercial processing lines to determine the impact of each stage on bacterial spore populations. Mesophilic aerobic, mesophilic anaerobic, thermophilic aerobic, and Bacillus cereus spore populations were enumerated in all the samples. Genetic diversity in B. cereus strains (n = 110) isolated from the samples was examined by M13 sequence-based PCR typing, partial sequencing of the panC gene, and the presence/absence of ces and cspA genes. The counts of different groups of sporeforming bacteria varied amongst farms and processing lines. For example, the counts of mesophilic aerobic spore-forming (MAS) populations of cocoa bean fermentation were lower than 1 log spore/g in Farm 1 but higher than 4 log spore/g in Farm 2. B. cereus isolated from cocoa powder was also recovered from cocoa beans, nibs, and samples after roasting, refining, and pressing, which indicated that B. cereus spores persist throughout cocoa processing. Phylogenetic group IV was the most frequent (73%), along with processing. Strains from phylogenetic group III (14 %) did not show the ces gene's presence.

The Deletion of LeuRS Revealed Its Important Roles in Osmotic Stress Tolerance, Amino Acid and Sugar Metabolism, and the Reproduction Process of Aspergillus montevidensis

Aspergillus montevidensis is an important domesticated fungus that has been applied to produce many traditional fermented foods under high osmotic conditions. However, the detailed mechanisms of tolerance to osmotic stress remain largely unknown. Here, we construct a target-deleted strain (ΔLeuRS) of A. montevidensis and found that the ΔLeuRS mutants grew slowly and suppressed the development of the cleistothecium compared to the wide-type strains (WT) under salt-stressed and non-stressed conditions. Furthermore, differentially expressed genes (p < 0.001) governed by LeuRS were involved in salt tolerance, ABC transporter, amino acid metabolism, sugar metabolism, and the reproduction process. The ΔLeuRS strains compared to WT strains under short- and long-term salinity stress especially altered accumulation levels of metabolites, such as amino acids and derivatives, carbohydrates, organic acids, and fatty acids. This study provides new insights into the underlying mechanisms of salinity tolerance and lays a foundation for flavor improvement of foods fermented with A. montevidensis.

Study of co-occurrence of mycotoxins in cocoa beans in Brazil by liquid chromatography-tandem mass spectrometry (LC-MS/MS)

In this study, 135 samples of cocoa beans collected in the Amazon and Atlantic Forest regions of Brazil were analysed to evaluate the possible co-occurrence of 34 mycotoxins. The results indicate that 42% of the cocoa samples exhibited quantifiable levels for 11 mycotoxins: aflatoxins (AFs) B1, B2 and G1; ochratoxin A; citrinin; cyclopiazonic acid; tenuazonic acid; paxilline; sterigmatocystin; zearalenone and fumonisin B2. Of the samples, 18% exhibited the co-occurrence of up to six mycotoxins. No toxins belonging to the groups of trichothecenes or ergot alkaloids were detected. Contingency analysis of the incidence of mycotoxins did not show significant differences between the two regions evaluated. Seven samples were contaminated with AFs, while only one contained ochratoxin A above 10 μg kg-1. The accuracy of the method was evaluated by proficiency testing for ochratoxin A, where satisfactory Z-scores were obtained.

Microbial Characterization of Retail Cocoa Powders and Chocolate Bars of Five Brands Sold in Italian Supermarkets

A microbial characterization of cocoa powder and chocolate bars of three batches of five different brands sold in Italian markets was performed. The results showed a variable microbial population consisting of mesophilic and thermophilic spore formation in both types of products. The chocolate bars were also contaminated with molds of environmental origin. Bacillus spp. and Geobacillus spp. were found in both products. The chocolate bars were also contaminated by molds belonging to the genera Penicillium and Cladosporium. The sporogenous strains mainly originate from the raw materials, i.e., cocoa beans, as the heat treatments involved (roasting of the beans and conching of the chocolate) are not sufficient to reach commercial sterility. Furthermore, the identified spore-forming species have often been isolated from cocoa beans. The molds isolated from chocolate seem to have an origin strictly linked to the final phases of production (environment and packaging). However, the level of contaminants is limited (<2 log CFU/g); the molds do not develop in both products due to their low Aw (<0.6) and do not affect the safety of the products. However, a case of mold development in chocolate bars was observed. Among the isolated molds, only Penicillium lanosocoeruleum demonstrated a high xero-tolerance and grew under some conditions on chocolate bars. Its growth could be explained by a cocoa butter bloom accompanied by the presence of humidity originating from the bloom or acquired during packaging.

Microbial Community Analysis in Sichuan South-road Dark Tea Piled Center at Pile-Fermentation Metaphase and Insight Into Organoleptic Quality Development Mediated by Aspergillus niger M10

Microbes are critical in the Sichuan South-road Dark Tea (SSDT) organoleptic quality development during pile-fermentation. Piled tea center at fermenting metaphase is crucial for the conversion of its quality components. In this study, we investigated the microbial community of piled SSDT center below the stacked tea surface of 15 cm (SSDTB), 50 cm (SSDTX), and 85 cm (SSDTH) on the second turning time of pile-fermentation, respectively. Results showed that SSDTH and SSDTB had a higher similarity in the microbial community. Pantoea (36.8%), Klebsiella (67.7%), and Aspergillus (35.3%) were the most abundant in SSDTH, SSDTB, and SSDTX, respectively. We found 895 species were common among all samples, but 86, 293, and 36 species were unique to SSDTB, SSDTX, and SSDTH, respectively. Aspergillus niger showed high co-occurrence and was positively correlated with numerous microbes in SSDT samples, and Aspergillus niger M10 isolated from SSDTX was excellent at enhancing soluble sugar (SS), amino acids (AAs), theaflavin (TF), and thearubigins (TR) contents, while decreasing catechin (Cat), tea polyphenols (TPs)/AA, Caf/SS, Cat/SS, TPs/SS, and (TPs + Caf)/SS levels in AM10 post-fermentation, as compared with the control. Moreover, it also produced a noticeable difference in the CIELab parameters in dried, liquor, and infused tea colors between AM10 and control during fermentation. When it was further inoculated on differential mediums, we detected glycoside hydrolases, namely, β-glucosidase, mannosidase, pectinase, cellulase, amylase, and α-galactosidase being secreted by Aspergillus niger M10. Taken together, SSDXT presented a more unique microbial community. Aspergillus niger M10 probably improved the sweet and mellow taste, and the yellow brightness and red color of SSDT during fermentation. It also provided new insights into the microbial profile and organoleptic quality development mechanism of SSDT during pile-fermentation.

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.

Functional role of yeasts, lactic acid bacteria and acetic acid bacteria in cocoa fermentation processes

Cured cocoa beans are obtained through a post-harvest, batchwise process of fermentation and drying carried out on farms in the equatorial zone. Fermentation of cocoa pulp-bean mass is performed mainly in heaps or boxes. It is made possible by a succession of yeast, lactic acid bacteria (LAB) and acetic acid bacteria (AAB) activities. Yeasts ferment the glucose of the cocoa pulp into ethanol, perform pectinolysis and produce flavour compounds, such as (higher) alcohols, aldehydes, organic acids and esters. LAB ferment the glucose, fructose and citric acid of the cocoa pulp into lactic acid, acetic acid, mannitol and pyruvate, generate a microbiologically stable fermentation environment, provide lactate as carbon source for the indispensable growth of AAB, and contribute to the cocoa and chocolate flavours by the production of sugar alcohols, organic acids, (higher) alcohols and aldehydes. AAB oxidize the ethanol into acetic acid, which penetrates into the bean cotyledons to prevent seed germination. Destruction of the subcellular seed structure in turn initiates enzymatic and non-enzymatic conversions inside the cocoa beans, which provides the necessary colour and flavour precursor molecules (hydrophilic peptides, hydrophobic amino acids and reducing sugars) for later roasting of the cured cocoa beans, the first step of the chocolate-making.

Methodology development based on "dilute and shoot" and QuEChERS for determination of multiple mycotoxins in cocoa by LC-MS/MS

This work proposes an extraction method based on the "dilute and shoot" approach and QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) for the simultaneous determination of 42 mycotoxins (34 quantified and 8 qualitatively studied) in dried cocoa bean samples. The purpose of the developed methodology was the reduction of co-extractives from the matrix and an efficient extraction without a cleanup step, and subsequent analysis by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). In order to obtain the best extraction conditions, gravimetric tests were performed and parameters that influenced the extraction efficiency were evaluated, such as the proportion of extraction phases, amount of salt, acidification, and extraction time. The performance of the developed method was evaluated to ensure its reliability. Considering the recovery range of 70-120% as an accuracy parameter, four of the mycotoxins under study (acetyl T-2, tenuazonic acid, wortmannin, and zearalenone) showed undesirable values at one of the levels evaluated. The repeatability of the method was assessed for 34 mycotoxins by the relative standard deviation (RSD%) of the responses, and all presented satisfactory values. The quantification limits ranged from 1.0 to 33.0 μg kg^-1. Modification of the extraction methods made it possible to simultaneously analyze multiple mycotoxins, eliminating the need for the cleanup step, which led to analyte losses. The proposed methodology has a low cost, which makes it advantageous in routine analysis. It also has the potential for scope extension to cocoa-based foods, which are naturally exposed to a greater variety of mycotoxins. Graphical abstract.

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.

Understanding Mycotoxin Contamination Across the Food Chain in Brazil: Challenges and Opportunities

Brazil is one of the largest food producers and exporters in the world. In the late 20th century, the European Union program for the harmonization of regulations for contaminants in food, including mycotoxins, led to the examination of mycotoxin contamination in foods at a global level. The problem of the rejection of food by the European Union and other countries became a Brazilian national priority because of economic and food safety aspects. Ochratoxin A in coffee and cocoa and aflatoxins in Brazil nuts are examples of the impact of technical trade barriers on Brazilian foods. To overcome these threats, several strategies were undertaken by Brazilian and international organizations. In this context, the Codex Commission on Food Contaminants (CCCF) has emerged as a forum to discuss with more transparency issues related to mycotoxins, focusing on establishing maximum levels and codes of practices for some commodities and mycotoxins to ensure fair trade and food safety. Our experience in investigating and understanding mycotoxin contamination across the food chains in Brazil has contributed nationally and internationally to providing some answers to these issues.

Aflatoxins and ochratoxin A in chocolate products in Turkey

This survey describes the occurrence and levels of AFs and OTA in chocolate products consumed in Turkey. A total of 130 samples, including bitter chocolate, milk chocolate and chocolate wafers were analysed for these mycotoxins by high-performance liquid chromatography coupled with fluorescence detection (HPLC-FLD). The values of recovery (81-92%) and precision (RSD < 9%) fulfilled the requirements of EC Regulation No. 401/2006. OTA was the most prevalent mycotoxin, with an incidence of 46.7% in bitter chocolate, 22.8% in milk chocolate and 17.4% in chocolate wafers, ranging from 0.18 to 0.75 μg kg^-1. AFs were detected in 13.3% of bitter chocolate, in 19.6% of milk chocolate and in 8.7% of chocolate wafers, in concentrations ranging from 0.15 to 2.04 μg kg^-1.

Cocoa and chocolate are sources of vitamin D2

Cocoa beans are susceptible to fungal contamination and often contain substantial amounts of ergosterol, the precursor to vitamin D₂. We hypothesized that sun-drying the fermented cocoa beans might lead to the conversion of ergosterol to vitamin D₂. We quantified vitamin D in cocoa and cocoa-based foods by liquid chromatography-tandem mass spectrometry. Here, we show that cocoa beans from different growing regions contain vitamin D₂. Particularly high vitamin D₂ content was found in cocoa powder and butter. Among the chocolates, dark chocolate had the highest vitamin D₂ content (ranging from 1.90 to 5.48 µg/100 g), white chocolate had the lowest vitamin D₂ content (ranging from 0.19 to 1.91 µg/100 g), and chocolate nut spreads had a comparatively low vitamin D₂ content, with an average of 0.15 µg/100 g. Thus, cocoa and chocolate are clearly a dietary source of vitamin D, therefore, it is necessary to update food composition databases.

Occurrence, distribution and contamination levels of heat-resistant moulds throughout the processing of pasteurized high-acid fruit products

Heat-resistant moulds (HRMs) are well known for their ability to survive pasteurization and spoil high-acid food products, which is of great concern for processors of fruit-based products worldwide. Whilst the majority of the studies on HRMs over the last decades have addressed their inactivation, few data are currently available regarding their contamination levels in fruit and fruit-based products. Thus, this study aimed to quantify and identify heat-resistant fungal ascospores from samples collected throughout the processing of pasteurized high-acid fruit products. In addition, an assessment on the effect of processing on the contamination levels of HRMs in these products was carried out. A total of 332 samples from 111 batches were analyzed from three processing plants (=three processing lines): strawberry puree (n = 88, Belgium), concentrated orange juice (n = 90, Brazil) and apple puree (n = 154, the Netherlands). HRMs were detected in 96.4% (107/111) of the batches and 59.3% (197/332) of the analyzed samples. HRMs were present in 90.9% of the samples from the strawberry puree processing line (1-215 ascospores/100 g), 46.7% of the samples from the orange juice processing line (1-200 ascospores/100 g) and 48.7% of samples from the apple puree processing line (1-84 ascospores/100 g). Despite the high occurrence, the majority (76.8%, 255/332) of the samples were either not contaminated or presented low levels of HRMs (<10 ascospores/100 g). For both strawberry puree and concentrated orange juice, processing had no statistically significant effect on the levels of HRMs (p > 0.05). On the contrary, a significant reduction (p < 0.05) in HRMs levels was observed during the processing of apple puree. Twelve species were identified belonging to four genera - Byssochlamys, Aspergillus with Neosartorya-type ascospores, Talaromyces and Rasamsonia. N. fumigata (23.6%), N. fischeri (19.1%) and B. nivea (5.5%) were the predominant species in pasteurized products. The quantitative data (contamination levels of HRMs) were fitted to exponential distributions and will ultimately be included as input to spoilage risk assessment models which would allow better control of the spoilage of heat treated fruit products caused by heat-resistant moulds.

State-of-the-Art Chocolate Manufacture: A Review

The aroma, taste, shine, snap, smoothness, "melt-in-your-mouth" sensation, and texture are all qualities that define chocolate, and all depend on how the cocoa and the chocolate itself are processed. Postharvest handling of the cocoa (fermentation, drying, cleaning, storage, and transport) and its transformation into chocolate (roasting, grinding, conching, tempering, molding, and the addition of core and other ingredients), as well as the packaging, storage, transport, and refrigeration of the finished product all have an important influence on the characteristics of chocolate. The aim of this review was to identify and study the key factors, including microbiological aspects that affect the quality of chocolate, from harvesting the beans right up to the manufacture of the finished products.

Isolation, Characterization, and Selection of Molds Associated to Fermented Black Table Olives

Table olives are one of the most important fermented food in the Mediterranean countries. Apart from lactic acid bacteria and yeasts that mainly conduct the olive fermentation, molds can develop on the brine surface, and can have either deleterious or useful effects on this process. From the food safety point of view, occurring molds could also produce mycotoxins, so, it is important to monitor and control them. In this respect, identification of molds associated to two Italian and two Greek fermented black table olives cultivars, was carried out. Sixty strains were isolated and molecularly identified as Penicillium crustosum (21), P. roqueforti (29), P. paneum (1), P. expansum (6), P. polonicum (2), P. commune (1). A group of 20 selected isolates was subjected to technological (beta-glucosidase, cellulolytic, ligninolytic, pectolytic, and xylanolytic activities; proteolytic enzymes) and safety (biogenic amines and secondary metabolites, including mycotoxins) characterization. Combining both technological (presence of desired and absence of undesired enzymatic activities) and safety aspects (no or low production of biogenic amines and regulated mycotoxins), it was possible to select six strains with biotechnological interest. These are putative candidates for future studies as autochthonous co-starters with yeasts and lactic acid bacteria for black table olive production.

Food Evolution: The Impact of Society and Science on the Fermentation of Cocoa Beans

Cocoa is part of the cultural heritage in many areas of South and Central America and has played an important role in the history of human culture there. The modern methods of cocoa bean production for the purpose of the manufacture of modern chocolate are tied to the origin and development of cocoa bean fermentation and processing methods and the science of microbiology. To date, however, there has not been a study that discusses the impacts of both science and culture on the evolution of cocoa beans and cocoa bean processing. This work provides both a detailed overview of the evolution and historical development of cocoa, from its earliest forms to modern chocolate manufacturing, an in-depth discussion of the biochemistry of cocoa bean fermentation, as well as a compilation of primary research studies with details on fermentation methods, the scientific bases of interactions in microbial fermentations, and methods for their investigation, as well as metabolites that are produced. As a result, we present here the major microorganisms among all the ones that have been identified in previous studies. This database will aid researchers seeking standardized inoculants to drive cocoa bean fermentation, as well as serve as a guide for inventorying and assessing other food evolution-related studies regarding traditional and artisanal-based food systems.

Impact of food processing and detoxification treatments on mycotoxin contamination

Mycotoxins are fungal metabolites commonly occurring in food, which pose a health risk to the consumer. Maximum levels for major mycotoxins allowed in food have been established worldwide. Good agricultural practices, plant disease management, and adequate storage conditions limit mycotoxin levels in the food chain yet do not eliminate mycotoxins completely. Food processing can further reduce mycotoxin levels by physical removal and decontamination by chemical or enzymatic transformation of mycotoxins into less toxic products. Physical removal of mycotoxins is very efficient: manual sorting of grains, nuts, and fruits by farmers as well as automatic sorting by the industry significantly lowers the mean mycotoxin content. Further processing such as milling, steeping, and extrusion can also reduce mycotoxin content. Mycotoxins can be detoxified chemically by reacting with food components and technical aids; these reactions are facilitated by high temperature and alkaline or acidic conditions. Detoxification of mycotoxins can also be achieved enzymatically. Some enzymes able to transform mycotoxins naturally occur in food commodities or are produced during fermentation but more efficient detoxification can be achieved by deliberate introduction of purified enzymes. We recommend integrating evaluation of processing technologies for their impact on mycotoxins into risk management. Processing steps proven to mitigate mycotoxin contamination should be used whenever necessary. Development of detoxification technologies for high-risk commodities should be a priority for research. While physical techniques currently offer the most efficient post-harvest reduction of mycotoxin content in food, biotechnology possesses the largest potential for future developments.

Incidence, populations and diversity of fungi from raw materials, final products and air of processing environment of multigrain whole meal bread

This study aimed to assess the incidence, to quantify and to assess the diversity of fungi in a multigrain whole meal bread processing plant. Two hundred and eight one (n=281) samples were analyzed, including raw materials (n=120), air samples (n=136) and multigrain breads (n=25). Among the raw materials, the whole corn flour showed the highest counts of fungi (4.8logCFU/g), followed by whole-wheat flour (3.1logCFU/g). The counts of fungi in the air of processing environment were higher in post-baking steps (oven output, cooling, slicing, packaging) than in pre-baking steps (weighing and mixer) (p<0.05). Species of fungi isolated from spoiled bread samples stored at 5, 20, 25 and 30, and 40°C corresponded mostly to Penicillium paneum and Penicillium polonicum isolated from 20 and 24% of samples, respectively. These species were also isolated from raw materials (P. paneum and P. polonicum) and air collected at different processing sampling points (P. polonicum). The high counts of filamentous fungi in raw materials and air samples in processing steps such as cooling, slicing, and packaging, suggest that contamination that may occur in these steps can be critical for the shelf life of breads. The results of this study highlight that the prevention of contamination of breads by fungal spores is still a challenge for bakery industries and that other strategies such as control of germination and growth of spoilage fungi through the development of more stable formulations have to be developed.

Portable and low cost fluorescence set-up for in-situ screening of Ochratoxin A

The present article describes a portable and low cost fluorescence set-up designed and characterized for in-situ screening of Ochratoxin A (OTA) in cocoa samples at field settings. The sensing module (the set up) consists of a LED with the wavelength of 370-380nm and a color complementary metal oxide semiconductor (CMOS) micro-camera inbuilt at upright position of a black box to obtain an image of the sensing molecule. It allows the user to get an image of the sensing analytes under excitation conditions and process the image in order to predict the toxicity of the samples. The image capturing and processing of the system was based on the OTA concentration in the sample and analyzed data can be presented as RGB values. For each concentration of the OTA, the R, G, B co-ordinates were obtained and plotted to quantify actual OTA presents in the sample. Moreover, the system was tested for real sample analysis using cocoa contaminated with OTA. The system could detect OTA as low as 1.25ng/ml with the maximum recovery of 87.5% in cocoa samples. The OTA was extracted in 1% NaHCO3 and cleaned up using molecular imprinted polymer column (MIP). The method demonstrated a good linear range between 1.25 and 10ng/ml. The obtained results were cross validated using chromatographic method HPLC and also compared with commercially available fluorescence instrument. The developed fluorescence setup is simple, economical, and portable with added advantages of digital image processing. The system could be deployable to cocoa fields for monitoring of OTA in quick successions. It is noteworthy to mention that this is the first report of such portable fluorescence setup where, OTA sensing was explored.

Conidia survival of Aspergillus section Nigri, Flavi and Circumdati under UV-A and UV-B radiation with cycling temperature/light regime

BACKGROUND

Bio-geographical differences in fungal infection distribution have been observed around the world, confirming that climatic conditions are decisive in colonization. This research is focused on the impact of ultraviolet radiation (UV) on Aspergillus species, based on the consideration that an increase in UV-B radiation may have large ecological effects.

RESULTS

Conidia of six mycotoxigenic Aspergillus species isolated from vineyards located in the northeast and south of Spain were incubated for 15 days under light/dark cycles and temperatures between 20 and 30 °C per day. Additionally, 6 h of exposure to UV-A or UV-B radiation per day were included in the light exposure. UV irradiance used were 1.7 ± 0.2 mW cm(-2) of UV-A (peak 365 nm) and 0.10 ± 0.2 mW cm(-2) of UV-B (peak 312 nm). The intrinsic decrease in viability of conidia over time was accentuated when they were UV irradiated. UV-B radiation was more harmful.

CONCLUSION

Conidial sensitivity to UV light was marked in Aspergillus section Circumdati. Conidia pigmentation could be related to UV sensitivity. Different resistance was observed within species belonging to sections Flavi and Nigri. An increase in UV radiation could lead to a reduction in the Aspergillus spp. inoculum present in the field (vineyards, nuts, cereal crops). In addition, it could unbalance the spore species present in the field, leading to a higher predominance of dark-pigmented conidia.

Sensitive analytical performance of folding based biosensor using methylene blue tagged aptamers

This work demonstrates the development of a folding based electrochemical aptasensor using methylene blue (MB) tagged anti-Ochratoxin A (OTA) aptamers. Different aptamer coupling strategies were tested using Hexamethylenediamine, polyethylene glycol, simple adsorption and diazonium coupling mechanism. The best sensitivity was recorded by oxidation of amines using hexamethylenediamine (HDMA) on screen printed carbon electrode (SPCE). To achieve the direct detection of OTA, aptamer conjugated redox probe was used and detection was demonstrated based on the conformational changes in aptamer structure upon OTA sensing. Signaling in this class of sensors arises from changes in electron transfer efficiency upon target-induced changes in the conformation/flexibility of the aptamer probe. These changes can be readily recorded electrochemically. The developed aptasensor is unique in its own mechanism as redox probe tagged aptamer coupling such as MB has never been tried to immobilize using long carbon chain spacers as, addition of spacers would provide more sensitive detection methods. A good dynamic range 0.01-5ng/ml was obtained for OTA with Limit of detection (LOD) 0.01ng/ml and Limit of quantification (LOQ) of 0.03ng/ml respectively. The good reproducibility was recorded with RSD% of 3.75. The obtained straight line equation was y=0.4035x+0.90311, r=0.9976. We believe that the sensor design guidelines outlined here represents a general strategy for developing new folding-based electrochemical aptasensors. The developed aptasensor was extended to screen cocoa samples for OTA contamination. The cocoa samples were extracted and purified using molecular imprinted polymer (MIP) columns. The aptasensor displayed good recovery values in the range 84-85% thus, exhibited the effectiveness of proposed aptasensor for such complex matrices.

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.

A label free aptasensor for Ochratoxin A detection in cocoa beans: An application to chocolate industries

Contamination of food by mycotoxin occurs in minute/trace quantities. Nearly 92.5% of the cocoa samples present Ochratoxin A (OTA) levels at trace quantity. Hence, there is a necessity for a highly sensitive and selective device that can detect and quantify these organic toxins in various matrices such as cocoa beans. This work reports for the first time, a facile and label-free electrochemical impedimetric aptasensor for rapid detection and quantitation of OTA in cocoa beans. The developed aptasensor was constructed based on the diazonium-coupling reaction mechanism for the immobilization of anti-OTA-aptamer on screen printed carbon electrodes (SPCEs). The aptasensor exhibited a very good limit of detection (LOD) as low as 0.15 ng/mL, with added advantages of good selectivity and reproducibility. The increase in electron transfer resistance was linearly proportional to the OTA concentration in the range 0.15-2.5 ng/mL, with an acceptable recovery percentage (91-95%, RSD = 4.8%) obtained in cocoa samples. This work can facilitate a general model for the detection of OTA in cocoa beans based on the impedimetric aptasensor. The analysis can be performed onsite with pre-constructed and aptamer modified electrodes employing a portable EIS set up.

Detection and identification of xerophilic fungi in Belgian chocolate confectionery factories

Chocolate confectionery fillings are generally regarded as microbiologically stable. The stability of these fillings is largely due to the general practice of adding either alcohol or preservatives. Consumer demands are now stimulating producers to move away from adding alcohol or other preservatives to their confectionery fillings and instead to search for innovative formulations. Such changes in composition can influence the shelf life of the product and may lead to spoilage by xerophilic fungi. The aim of this study was to test whether the production environment of Belgian chocolate confectionery factories and common ingredients of chocolate confectioneries could be potential sources of contamination with xerophilic fungal species. In the factory environment, the general and strictly xerophilic fungal spore load was determined using an RCS Air Sampler device in combination with DG18 and MY50G medium, respectively. Four basic ingredients of chocolate confectionery fillings were also examined for fungal spore levels using a direct plating technique. Detected fungi were identified to species level by a combination of morphological characterization and sequence analysis. Results indicated a general fungal spore load in the range of 50-250 colony forming units per cubic meter of air (CFU/m(3) air) and a more strict xerophilic spore load below 50 CFU/m(3) air. These results indicate rather low levels of fungal spores present in the factory environment. The most prevalent fungi in the factory environment were identified as Penicillium spp., particularly Penicillium brevicompactum. Examination of the basic ingredients of confectionery fillings revealed nuts to be the most likely potential source of direct contamination. In nuts, the most prevalent fungal species identified were Eurotium, particularly Eurotium repens.

Computational fluid dynamics approaches in quality and hygienic production of semisolid low-moisture foods: a review of critical factors

Low-moisture foods have been responsible for a number of salmonellosis outbreaks worldwide over the last few decades, with cross contamination from contaminated equipment being the most predominant source. To date, actions have been focused on stringent hygienic practices prior to production, namely periodical sanitization of the processing equipment and lines. Not only does optimum sanitization require in-depth knowledge on the type and source of contaminants, but also the heat resistance of microorganisms is unique and often dependent on the heat transfer characteristics of the low-moisture foods. Rheological properties, including viscosity, degree of turbulence, and flow characteristics (for example, Newtonian or non-Newtonian) of both liquid and semisolid foods are critical factors impacting the flow behavior that consequently interferes heat transfer and related control elements. The demand for progressively more accurate prediction of complex fluid phenomena has called for the employment of computational fluid dynamics (CFD) to model mass and heat transfer during processing of various food products, ranging from drying to baking. With the aim of improving the quality and safety of low-moisture foods, this article critically reviewed the published literature concerning microbial survival in semisolid low-moisture foods, including chocolate, honey, and peanut butter. Critical rheological properties and state-of-the-art CFD application relevant to quality production of those products were also addressed. It is anticipated that adequate prediction of specific transport properties during optimum sanitization through CFD could be used to solve current and future food safety challenges.

Mucormycoses caused by Lichtheimia species

Mucormycoses are life-threatening infections with fungi from the order Mucorales (Mucoromycotina). Although mucormycoses are uncommon compared to other fungal infections, e.g. aspergillosis and candidiasis, the number of cases is increasing especially in immunocompromised patients. Lichtheimia (formerly Absidia) species represent the second to third most common cause of mucormycoses in Europe. This mini review presents current knowledge about taxonomy and clinical relevance of Lichtheimia species. In addition, clinical presentation and risk factors will be discussed. Proper animal infection models are essential for the understanding of the pathogenesis and the identification of virulence factors of fungal pathogens. To date, several animal models have been used to study Lichtheimia infection. A brief overview of the different models and the main conclusions from the infection experiments is summarised in this review.

Gene expansion shapes genome architecture in the human pathogen Lichtheimia corymbifera: an evolutionary genomics analysis in the ancient terrestrial mucorales (Mucoromycotina)

Lichtheimia species are the second most important cause of mucormycosis in Europe. To provide broader insights into the molecular basis of the pathogenicity-associated traits of the basal Mucorales, we report the full genome sequence of L. corymbifera and compared it to the genome of Rhizopus oryzae, the most common cause of mucormycosis worldwide. The genome assembly encompasses 33.6 MB and 12,379 protein-coding genes. This study reveals four major differences of the L. corymbifera genome to R. oryzae: (i) the presence of an highly elevated number of gene duplications which are unlike R. oryzae not due to whole genome duplication (WGD), (ii) despite the relatively high incidence of introns, alternative splicing (AS) is not frequently observed for the generation of paralogs and in response to stress, (iii) the content of repetitive elements is strikingly low (<5%), (iv) L. corymbifera is typically haploid. Novel virulence factors were identified which may be involved in the regulation of the adaptation to iron-limitation, e.g. LCor01340.1 encoding a putative siderophore transporter and LCor00410.1 involved in the siderophore metabolism. Genes encoding the transcription factors LCor08192.1 and LCor01236.1, which are similar to GATA type regulators and to calcineurin regulated CRZ1, respectively, indicating an involvement of the calcineurin pathway in the adaption to iron limitation. Genes encoding MADS-box transcription factors are elevated up to 11 copies compared to the 1-4 copies usually found in other fungi. More findings are: (i) lower content of tRNAs, but unique codons in L. corymbifera, (ii) Over 25% of the proteins are apparently specific for L. corymbifera. (iii) L. corymbifera contains only 2/3 of the proteases (known to be essential virulence factors) in comparison to R. oryzae. On the other hand, the number of secreted proteases, however, is roughly twice as high as in R. oryzae.

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.

Microbiota dynamics and diversity at different stages of industrial processing of cocoa beans into cocoa powder

We sampled a cocoa powder production line to investigate the impact of processing on the microbial community size and diversity at different stages. Classical microbiological methods were combined with 16S rRNA gene PCR-denaturing gradient gel electrophoresis, coupled with clone library construction, to analyze the samples. Aerobic thermoresistant spores (ThrS) (100°C; 10 min) were also isolated and characterized (identity, genetic diversity, and spore heat resistance), in view of their relevance to the quality of downstream heat-treated cocoa-flavored drinks. In the nibs (broken, shelled cocoa beans), average levels of total aerobic microorganisms (TAM) (4.4 to 5.6 log CFU/g) and aerobic total spores (TS) (80°C; 10 min; 4.3 to 5.5 log CFU/g) were significantly reduced (P < 0.05) as a result of alkalizing, while fungi (4.2 to 4.4 log CFU/g) and Enterobacteriaceae (1.7 to 2.8 log CFU/g) were inactivated to levels below the detection limit, remaining undetectable throughout processing. Roasting further decreased the levels of TAM and TS, but they increased slightly during subsequent processing. Molecular characterization of bacterial communities based on enriched cocoa samples revealed a predominance of members of the Bacillaceae, Pseudomonadaceae, and Enterococcaceae. Eleven species of ThrS were found, but Bacillus licheniformis and the Bacillus subtilis complex were prominent and revealed great genetic heterogeneity. We concluded that the microbiota of cocoa powder resulted from microorganisms that could have been initially present in the nibs, as well as microorganisms that originated during processing. B. subtilis complex members, particularly B. subtilis subsp. subtilis, formed the most heat-resistant spores. Their occurrence in cocoa powder needs to be considered to ensure the stability of derived products, such as ultrahigh-temperature-treated chocolate drinks.

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.

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.