Food Mycology Research Articles

Thermal and digital imaging information acquisition regarding the development of Aspergillus flavus in pistachios against Aspergillus carbonarius in table grapes

The phenotypic diagnostics in food mycology exhibit hysteresis in fungal detection during the early stages since hyphal and fruiting structures become visible only in advanced growth stage. Aspergillus flavus is a saprotrophic and pathogenic fungus colonizing cereal grains, legumes, and tree nuts. This fungus produces significant quantities of aflatoxins which have nephrotoxic, hepatotoxic, teratogenic and immunosuppressive effects on humans. The spatial temperature heterogeneity of A. flavus in infected pistachios was assessed by means of thermal imaging along with the digital RGB imaging analysis. The image analysis in terms of hue angle, exhibited not significant variation of non-infected pistachios compared to the infected ones at the early stages of fungal invasion but it became significantly different 72 h since infection. The fungal growth rate was assessed by comparing the Weibull shape factor of pistachios inoculated with A. flavus against grapes inoculated with A. carbonarius. The latter showed that the first 6 h since inoculation showed similar growth rate (∂β¯/∂t=6.7) while between 6 and 20 h showed lesser but almost double growth rate of the infected grapes (∂β¯grapes/∂t=5.4) against the infected pistachios (∂β¯pistachios/∂t=2.2). Infected pistachios and grapes were both stored at 28 °C and 60% RH, hence, the noted variation in growth rate should be fungus and substrate dependent. The peak of the temporal variation of the Weibull shape factor in pistachios and grapes extends between 15 and 20 h since inoculation, while for the infected grapes it is 71% higher than the one of the infected pistachios, revealing a distinctive fungal growth rate.

Study of Fungi on Stored Maize (Zea mays L.) in Kebbi State, Nigeria

The present study was carried out to determine the fungal species associated with stored Maize from three villages: Sabiyel, Dan warai and Jiga all within Aliero L.G.A. From each village, twenty spike of silo maize were collected, making a total of sixty samples. Fungi were investigated using the standard procedure recommended by the International Commission on Food Mycology (ICFM). Eight fungal species were isolated and identified from the results obtained; Aspergillus niger, Mucor racemosus, Aspergillus fumagatus, Aspergillus terries, Fusarium species, Ceplosporium species, Aspergillus flavus and Penicillium species. Aspergillus niger had the highest mean frequency and percentage 3.00 (16.60%) while the lowest was obtained in Penicillium species 1.67 (9.77%). Jiga village had the highest fungal rate of 87.5% and Sabiyel with the lowest 75% based on locations. In conclusion, it was observed that perishable agricultural food is susceptible to spoilage by fungi, probably because these organisms' spores are easily transmitted via the air, during transportation, harvest, handling, and preservations of these products might lead to spoilage of stored maize grains. There is a need for proper storage techniques, farmers' awareness of the health implications of these fungi, and adequate storage conditions in the study area to reduce contamination of store maize grains by these fungal isolates.

Preliminary study of black aspergilli inhabiting Piper rhizosphere from Eka Karya Botanical Garden, Bedugul Bali

The black aspergilli (Aspergillus section Nigri ) occupy a broad spectrum of habitat, and they are an essential group of species in food mycology, medical mycology, and biotechnology. This study aimed to isolate and identify the black aspergilli inhabiting five samples of Piper rhizosphere collected from Eka Karya Botanical Garden, Bedugul Bali. In this study, 71 strains of black aspergilli were isolated, and 20 strains of them have selected and characterized using morphological, molecular, and phylogenetic analysis. Morphological data results are useful for preliminary identification, but they did not have been totally effective in describing and elucidating 20 selected strains into species level. Further molecular identification and phylogenetic analysis based on ITS rDNA showed that from 20 selected strains, four strains were identified as Aspergillus aculeatus sensu stricto, three strains were identified as Aspergillus japonicus sensu stricto, four strains were identified as Aspergillus niger sensu lato, and nine strains were identified as Aspergillus tubingensis sensu stricto. Preliminary exploration of fungi through isolation and identification was the first step to discover the potential strains that able to produce the promising metabolites and bioactive materials. The study results are expected to be the initial microbial resources and information for screening and utilizing the black aspergilli through bioprospecting.

Development of thermography methodology for early diagnosis of fungal infection in table grapes: The case of Aspergillus carbonarius

Traditional diagnostic methods employed in food mycology are based on macroscopic and microscopic characteristics and culture in appropriate media. The macroscopic methods exhibit limitations in detecting fungal development before the fruiting structures become evident. One of the imaging techniques, which have attracted attention, is infrared thermography which has been used in non-destructive monitoring of physiological status of plants. The filamentous fungus Aspergillus carbonarius is the causal pathogen of sour rot of grapes and produces ochratoxin-A, the most important mycotoxin in grapes. Ochratoxin-A has been shown to be nephrotoxic, hepatotoxic, teratogenic and immunosuppressive properties with a tremendous impact on human health. In order to assess the spatial temperature heterogeneity in A. carbonarius infected table grapes, the average temperature of the berries surface as well as the maximum temperature difference between the infected and non-infected areas of berries’ surface were calculated. The average grape temperature during the development of the fungal mycelium in the berry was significantly lower than that of the healthy one, while the maximum temperature difference increased during the fungal colonization compared to the healthy grapes that stayed constant. The estimated shape factors derived by fitting the temperature data of the thermal images to the Weibull distribution was able to identify healthy from infected berry areas even during the very early stages of A. carbonarius infection.

“Cachaças” (Sugarcane Spirit) Aged Quantitation of Phenolic Compounds, Antibacterial and Antioxidant Activity

The “cacha&ccedila” is currently one of the fastest growing agro-industrial industries in the country as the drink considered as a symbol of Brazilian nationality. This study aimed to quantify the phenolic compounds, evaluate the antioxidant and antibacterial activity of different samples of aged “cacha&ccedila”. The physic-chemical analysis was performed at the Brandy Quality Laboratory of the Federal University of Lavras, and the determination of phenolic compounds was performed by High Performance Liquid Chromatography (HPLC). The antimicrobial activity evaluation was held at the Food Mycology Laboratory through the cavity agar diffusion technique and by steam using the micro-organisms Escherichia coli, Staphylococcus aureus, Salmonella choleraesuis, Listeria monocytogenes and Pseudomonas aeruginosa. The antioxidant activity was evaluated using the DPPH radical sequestering method. The values obtained for the phenolic compounds ranged from 0.41 to 9.69 mg/L, observing the predominance of syringaldehyde, gallic acid and vanillic acid. The phenolic extracts showed a satisfactory antibacterial activity for both Gram-negative and Gram-positive but did not show inhibition against the bacteria Pseudomonas aeruginosa. The antioxidant activity was evidenced by the DPPH test for cacha&ccedilas tested and the “cacha&ccedila” aged in oak barrel showed the highest activity, followed by “cacha&ccedila” aged in jequitiba, amburana and balm barrels.

Aspergillus fijiensis n. sp. isolated from bronchial washings in a human case of bronchiectasis with invasive aspergillosis: the first report

Introduction The black aspergilli (Aspergillus section Nigri) are an important group of species in food mycology, medical mycology and biotechnology. Many species cause food spoilage, but are also used in the fermentation industry. More recently they were shown to pose hazards to human and animal health as producers of ochratoxin A,

Quantification of Geotrichum candidum growth in co-culture with lactic acid bacteria

The growth dynamics of filamentous fungus G. candidum was studied during the co-cultivation with the commercial lactic acid bacteria (LAB) culture Fresco. The experiments were carried out in milk and on the surface of a milk agar at the temperature ranging from 5 to 37°C. Ratkowsky model was used to describe the relationships of the fungal growth rate to the temperature during both, single and co-cultivation with LAB in milk. Simultaneous growth of LAB affected significantly the growth rate of the filamentous fungus. The growth of G. candidum was in average 39% slower in the co-culture than in the single cultivation. LAB pre-inoculated and growing in the solid medium did not show any significant inhibitory effect on the surface growth of G. candidum at all tested temperature. The precise data describing the growth of this cheese yeast-like fungus, G. candidum, may fill a gap in the field of quantitative food mycology and may be used for predicting its behavior in real conditions.

Food mycology - a multifaceted approach to fungi and food

"Food mycology - a multifaceted approach to fungi and food." World Mycotoxin Journal, 1(2), pp. 223–224

Application of neural networks as a non-linear modelling technique in food mycology

Fungal growth leads to spoilage of food and animal feeds and to formation of mycotoxins and potentially allergenic spores. There is a growing interest in modelling microbial growth as an alternative to time-consuming, traditional, microbiological enumeration techniques. Several statistical models have been reported to describe the growth of different micro-organisms however the nature of neural networks, as highly non-linear approximator schemes, considers them as an alternative methodology. The application of neural networks in predictive microbiology is presented in this paper. This technique was used to build up a model of the joint effect of water activity, pH level and temperature to predict the maximum specific growth rate of the ascomycetous fungus Monascus ruber. Neural network and polynomial models were compared against the experimental data using six statistical indices namely, coefficient of determination (R^2), root mean square error (RMSE), mean relative percentage error (MRPE), mean absolute percentage error (MAPE), standard error of prediction (SEP), bias (Bf) and accuracy (Af) factors. Graphical plots were also used for model comparison. The performance of the learning-based systems provide encouraging results while sensitivity analysis showed that from the three environmental factors the most influential on fungal growth was temperature, followed by water activity and pH to a lesser extend. Neural networks offer an alternative and powerful technique to model microbial kinetic parameters and could thus become an additional tool in predictive mycology.

Book Review: Advances in Food Mycology

Book Review: Advances in Food Mycology

Study of a room temperature phosphorescence phenomenon to allow the detection of aflatoxigenic strains in culture media

A novel screening method based on room temperature phosphorescence (RTP) for the visual detection of aflatoxigenic strains from Aspergillus genus is described. Strains were cultured on media widely used in food mycology to which methyl-β-cyclodextrin plus bile salts (0.6% sodium deoxycholate) were added. Aflatoxin production was readily detectable after 3 days of incubation at 28 °C by RTP emission from the mycelium of aflatoxigenic strains observed after exposure to UV light. The method was tested on thirty-two Aspergillus sp. strains. The phosphorescence phenomenon was reproduced in vitro by immobilizing aflatoxin B 1 on ion exchange resin beads.

Advances in Food Mycology

Advances in Food Mycology

The system approach to the identification of aflatoxigenic fungi in foodstuffs and feedstuffs.

Aspergillus flavus, A parasiticus, A nomius, A tamarii andA pseudotamarii are important microorganisms capable of producing aflatoxins and further mycotoxins. Aflatoxigenic Aspergillus species are morphologically similar species belonging to the Aspergillus section Flavi. The aflatoxigenic fungal strains were isolated from foods (cereals, pulses, oilseeds, dried fruit, spices), soil, air and water. Mycological analyses are based on valid standards and recommendations of the International Commission for Food Mycology (ICFM). The identification of isolated aflatoxigenic fungi in foodstuffs and feedstuffs can be proved by using classical mycological cultivation methods, diagnostic nutrient media, chemotaxonomy and molecular biological methods (PCR). The system approach to the identification of aflatoxigenic fungi combines these four methods. Thirty strains of the aflatoxigenic fungi were tested.

The prevalence and control of spoilage yeasts in foods and beverages

Consumers in developed countries have a more critical attitude about what they eat and drink as a consequence of modern life. Food microbiologists are facing a huge challenge regarding food ‘freshness' implicit in the consumer's demand for more natural products. Food with less severe processing, that is additive-free, safer, with satisfactory shelf life and easy to prepare is sought because of higher consciousness about nutrition and health. Besides the development of new methods and preservation concepts, great advances in the fields of chemistry, biochemistry, microbiology, hygiene and food safety have occurred in recent decades. But are such developments properly used to respond to the challenge to food mycology? We will summarize the effects on food of yeast spoilage activity and we will reflect on how this activity can be monitored by food microbiologists.

Detection of Penicillium species in complex food samples using the polymerase chain reaction

Rapid identification of filamentous fungi is becoming increasingly important in food mycology both for monitoring the production process and for the identification of food spoilers. This paper describes the development and trial of two specifie PCR primer sets. A 336 bp fragment from species belonging to Penicillium subgenus Penicillium was amplified by the primers ITS 212d and ITS 549. The other primer set, ITS 183 and ITS 401 specifically identified two species. Penicillium roqueforti and P. carneum, both known as spoilers in the bread industry, by amplification of a 300 bp fragment. The future perspectives of PCR based identification of filamentous fungi in food are discussed.

Electronic nose for microbial quality classification of grains

The odour of grains is in many countries the primary criterion of fitness for consumption. However, smelling of grain for quality grading should be avoided since inhalation of mould spores or toxins may be hazardous to the health and determinations of the off-odours are subjective. An electronic nose, i.e. a gas sensor array combined with a pattern recognition routine might serve as an alternative. We have used an electronic nose consisting of a sensor array with different types of sensors. The signal pattern from the sensors is collected by a computer and further processed by an artificial neural network (ANN) providing the pattern recognition System. Samples of oats. rye and barley with different odours and wheat with different levels of ergosterol, fungal and bacterial colony forming units (cfu) were heated in a chamber and the gas in the chamber was led over the sensory array. The ANN could predict the odour classes of good, mouldy, weakly and strongly musty oats with a high degree of accuracy. The ANN also indicated the percentage of mouldy barley or rye grains in mixtures with fresh grains. In wheat a high degree of correlation between ANN predictions and measured ergosterol as well as with fungal and bacterial cfu was observed. The electronic nose can be developed to provide a simple and fast method for quality classification of grain and is likely to find applications also in other areas of food mycology.

Enumeration of xerophilic yeasts in the presence of xerophilic moulds: a collaborative study

A collaborative study was undertaken to compare the performance of Dichloran 18% Glycerol agar (DG18) with three other media widely used in food mycology, for the enumeration of xerophilic yeasts in the presence of xerophilic moulds. Oxytetracycline Glucose Yeast extract agar, (OGY), Dichloran Rose Bengal Chloramphenicol agar (DRBC) and Malt extract Yeast extract 50% Glucose agar (MY50G) were evaluated. Three reference samples (A, B, C) were prepared using skimmed milk powder inoculated with mixed lyophilized cultures of selected xerophilic yeasts and moulds, at levels around 10 4 to 10 5 CFU/g. Yeast species used were Candida glucosophila, C. versatilis, Zygosaccharomyces ballii and Z. rouxii, together with Eurotium spp. and some other moulds. Collaborators were asked to examine each sample twice, by dilution plating on the four media. Colonies were counted after 3, 5 and 7 days incubation at 25 °C. Fourteen participants from seven laboratories in six countries collaborated in this study. The ability of collaborators to detect and count yeasts after 5 and 7 days on DG18, DRBC and OGY varied depending on the sample. Few participants were able to count yeasts even after 7 days on MY50G. The overall results demonstrated that DG18 incubated 5 days at 25 °C was superior to the other three media tested for the enumeration of xerophilic yeasts in the presence of xerophilic moulds.

Analytical Mycology and Microscopy of Foods

Analytical Mycology and Microscopy of Foods

Food mycology—an emerging discipline

Food mycology—an emerging discipline

Methodological developments in food mycology

Methodological developments in food mycology