Use of the selective agar medium CREAD for monitoring the level of airborne spoilage moulds in cheese production

It was investigated if a selective medium for common cheese spoiling moulds (CREAD) could give more relevant information than a general mould medium in hygienic air-sampling in cheese factories. A total of 126 air-samples were taken in six Nordic cheese factories using the general mould medium DG18 and CREAD. The level and genera of air-borne mould was determined. Identification to species-level was performed for a selection of samples. In five cheese factories the mycobiota was dominated by Penicillium spp. and in one cheese factory by Cladosporium spp. The concentration of air-borne moulds varied between the cheese factories ranging from 1 to 270 cfu/m3 on DG18 with a median value of 17. The number of mould colonies was in general lower at CREAD. Identification indicated that CREAD supported growth of common spoilage moulds for cheese, such as Penicillium palitans and P. commune. The mycobiota on DG18 also consisted of moulds not commonly associated with spoilage of cheese, such as Cladosporium spp., P. brevicompactum and P. chrysogenum. Contamination of cheese with mould is periodically a problem in production of semi-hard cheese and the level of air-borne mould is therefore routinely monitored in cheese factories. A clear correlation between the total number of moulds in air and mould growth on products is not always found. The conclusion from the investigation is that it is recommended to use a selective medium for cheese spoilage moulds, such as CREAD in hygienic monitoring.     

Use of UV photography to identify aflatoxin-producing strains ofAspergillus flavus andA. parasiticus

UV photography in glucose, yeast extract (GY) agar medium was tested as a simple and rapid method for the distinction of afiatoxin-positive from aflatoxin-negative strains ofAspergillus flavus andA. parasiticus. In the UV photographs aflatoxin-producing moulds were identified as grey or black colonies, whereas aflatoxin-non-producing moulds appeared as white colonies. Of the afiatoxin-positive strains detected by the UV photographic method, 10% was confirmed by extraction of the GY agar medium and mould mycelium in chloroform, extracts which were analysed subsequently using thinlayer chromatography. Confirmation of aflatoxigenic strains was achieved by biosynthesis on liquid medium yeast extract sucrose (YES) broth.     

基于颜色特征的含黄曲霉毒素玉米颗粒的检出方法

为快速准确识别出感染黄曲霉毒素的玉米颗粒,基于黄曲霉毒素在365 nm紫外光照射下可发出黄绿色荧光(bright greenish-yellow fluorescence,BGYF)的特性,提出了一种以颜色为特征量的感染毒素颗粒的检出方法。首先针对同一组玉米颗粒样本分别获取其在紫外光和可见光下的2幅图像,对可见光图像进行二值化、颗粒区域填充等预处理操作,得到玉米颗粒的轮廓与位置信息;然后将进行彩色增强后的紫外光图像与预处理后的可见光图像掩膜;最后在掩膜图像中通过RGB模型中G通道下的阈值作为分割参数识别玉米颗粒上的感染区域。结果表明,所提出的识别方法对能够发出荧光的含黄曲霉菌玉米颗粒识别准确率达到84%以上,对含有黄曲霉毒素的正确检出率可达77.8%以上,能够达到区分检测的要求。     

传统干腌火腿中霉菌菌相构成及其安全性评价

对国内外传统干腌火腿中霉菌菌相组成、作用等方面进行了综述,并阐述了传统干腌火腿中霉菌的安全性评价。产毒霉菌的存在会给火腿带来潜在的危险性,因此通过对自然生长的霉菌分离纯化,筛选有益于火腿发色、成熟、产香和外观的菌株作为发酵剂,这是解决传统火腿制品安全性的一条重要途径。     

Spectral analyses of fluorescences in dent maize infected with Aspergillus flavus and Aspergillus parasiticus

Bright greenish yellow (BGYF) and blue white (BWF) fluorescences were associated with Aspergillus flavus and A. parasiticus infected maize. The fluorescences were studied spectrofluorometrically, the BGYF exhibiting a peak wave length between 480–485 nm and the BWF between 440–445 nm. Neither fluorescence varied in maize stored under different moistures and temperatures.

BWF was similar spectrally to the fluorescence of the endosperm of sound kernels but × 5 20 more intense. The spectrum of BWF was similar to Aflatoxin G₁ or a mixture of aflatoxin B₁, B₂, G₁ and G₂ when they were spotted on endosperm tissue. A color reference for BGYF was similar in peak wave length to BGYF. Amsoy soybeans without the seed coat fluoresced with a peak 470–475 nm and the intensity was low compared to BGYF in maize. A fluorescence of maize kernels visually similar to BGYF but not associated with Aspergillus infection or aflatoxin contamination was also investigated. This “false BGY” fluorescence was spectrally similar to the BGYF in infected kernels.     

Several physical properties of aflatoxin-contaminated pistachio nuts: Application of BGY fluorescence for separation of aflatoxin-contaminated nuts

The primary objective was to evaluate and find a proper method for visual identification of aflatoxin-contaminated pistachio nuts. The feasibility of using bright greenish yellow fluorescence (BGYF) in pistachio nut as a discriminating factor for identification of Aspergillus flavus-infested nuts, at harvest and in post-harvest, is investigated. Results show a strong relationship between BGYF and aflatoxin content at harvest. The factors affecting the application of this method in post-harvest stages are also discussed. The relationship between inside-brown kernels and aflatoxin presence is confirmed. At harvest, the brown kernels are a subdivision of fluorescent fraction. The share of different pistachios based on hull types (with sound hull, growth split and early-split) in contamination is studied. The early-split nuts are the most contaminated nuts, growth split nuts are less contaminated, and pistachios with sound hulls are almost clean. The effect of inappropriate handling on the percentage of fluorescent nuts is studied. The percentage of visible mould in samples is observed which shows a good relationship with the presence of BGY fluorescence.     

Use of UV photography to identify aflatoxin-producing strains ofAspergillus flavus andA. parasiticus

UV photography in glucose, yeast extract (GY) agar medium was tested as a simple and rapid method for the distinction of afiatoxin-positive from aflatoxin-negative strains ofAspergillus flavus andA. parasiticus. In the UV photographs aflatoxin-producing moulds were identified as grey or black colonies, whereas aflatoxin-non-producing moulds appeared as white colonies. Of the afiatoxin-positive strains detected by the UV photographic method, 10% was confirmed by extraction of the GY agar medium and mould mycelium in chloroform, extracts which were analysed subsequently using thinlayer chromatography. Confirmation of aflatoxigenic strains was achieved by biosynthesis on liquid medium yeast extract sucrose (YES) broth.     

Screening of tomato purée for excessive mould content by near infrared spectroscopy: A preliminary evaluation

Preliminary experiments demonstrated that near infrared spectroscopy (n. i. r.s.) could be used to measure the amount of mould (Botrytis cinerea or Alternaria tenuissima) added to fresh tomato homogenate. In subsequent work, fresh tomatoes that had been allowed to become mouldy were used to prepare a series of tomato purées containing known quantities of mouldy fruit. N.i.r.s. of the freeze-dried purée was again successful in estimating the amount of contamination as per cent mouldy fruit. Regression analysis selected wavelengths which could be associated with absorption bands of chitin, the major carbohydrate in the cell walls of moulds. It may therefore be possible to utilise n.i.r.s. as a screen for mould in tomato purées if the present success with B. cinerea and A. tenuissima can be extended to the complete range of moulds encountered in tomato products.     

Aspergillus section Flavi and aflatoxins in dried figs and nuts in Algeria

The presence of Aspergillus section Flavi and aflatoxin (AF) contamination was investigated in 112 samples of peanuts, almonds and dried figs collected in Algeria. The occurrence of aflatoxin B1 (AFB1), B2 (AFB2), G1 (AFG1) and G2 (AFG2) in different commodities has been determined with a sensitive method based on high performance liquid chromatography (HPLC) coupled with fluorescence detection with post-column photochemical derivatisation. Analytical results indicated that 28 samples of peanuts, 16 samples of almonds and 26 samples of dried figs contained detectable levels of AFs. A total of 69 samples (61.6%) were contaminated with AFB1 ranging from the limit of quantification to 174 µg kg^?1. AFB2 was found in 12 samples (10.7%) and varied from 0.18 to 193 µg kg^?1. Seven samples revealed AF concentrations lower than the limit of quantification. Eleven peanut and fourteen dried fig samples exceeded the European maximum limits for AFB1.     

浓香型白酒夏冬两季生产车间及大曲中霉菌与放线菌的分离纯化

为研究湖北咸宁浓香型黄鹤楼酒霉菌和放线菌的类型和特点,采用不同的培养基,对夏季和冬季车间样品微生物进行分离纯化及形态鉴别。结果表明,夏季车间空气中分离到15株霉菌,大曲中10株霉菌（104～105 CFU/g）,窖泥中1株霉菌和1株放线菌（102～103 CFU/g）。冬季车间空气中分离到9株霉菌,大曲中9株霉菌（104～105 CFU/g）,窖泥中7株霉菌（103～104 CFU/g）;窖泥霉菌菌落的气丝少,形态与空气及大曲中的主要霉菌差异显著。比较冬季和夏季样品,仅从冬季大曲的曲心和曲皮中分离到青霉,从夏季底泥中分离到一株放线菌,冬季的空气霉菌少于夏季,而冬季窖泥中的霉菌多于夏季。     

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

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

A MICROBIOLOGICAL EVALUATION OF BARLEY MALT PRODUCTION

The development of the microflora of barley malt was examined by direct and dilution plating. At all stages of the malting process mesophilic bacteria predominated. Viable counts of bacteria on green malt were 85–600 times greater than on the original barley, but fell to less than one-half of the original level with kilning. Corresponding increases in yeast and, especially, mould counts during malting were smaller. The yeast-like mould Geotrichum candidum was prominent in green malt. Although counts of yeasts and most moulds were considerably reduced by kilning, Mucor spp. proliferated during kilning.     

Fungal contamination of Kashar cheese in Turkey

Fifty random samples of Kashar cheese were collected from shops in different localities in Erzurum, all contained moulds. Mean count of total surface mould was 3.02 × 10¹⁰/g cheese and that of inner mould was 3.02 × 10³/g cheese. The genera Penicillium, Aspergillus, Mucor, Rhizopus and Geotrichum sp. were isolated from cheese samples. Aflatoxins were not detected in cheese samples. Potassium sorbate inhibited mould growth and sporulation in YES broth. The public health importance and economic significance of fungal contamination, and suggested measure for cheese quality are discussed.     

Immunological detection of moulds in food: relation between antigen production and growth

In a study of Notermans and Heuvelman (Int. J. Food Microbiol. (1985) 2, 247–258) an enzyme linked immunosorbent assay (ELISA) for detection of moulds was described. The ELISA used was based on detection of a heat stable, water extractable and genus specific antigen(s) produced by moulds. The results indicated the possibility of testing food products, whether or not heated, for mould contamination. In this study antigen(s) production by moulds was tested under different growth conditions. It was observed that production of antigen(s) was correlated with mycelium weight. Type of medium, including different fruit juices, did not affect the production of antigen(s). Also no differences between surface culturing and submerged culturing were observed. Both incubation temperature and water activity showed no significant effect on production of antigen(s). Within the genus Penicillium 43 out of 45 species tested produced identical antigen(s) in comparable quantities. The quantity of antigen(s), expressed as minimal detectable quantity of mould mycelium produced, varied from 6–108 ng/ml with an average of 32 ng/ml.     

Image-Based Screening for the Identification of Bright Greenish Yellow Fluorescence on Pistachio Nuts and Cashews

The development of screening methodologies for a rapid identification of crops contaminated with aflatoxin is of great interest to agro-food industry. The objective of this work was to develop an image algorithm able to identify bright greenish yellow fluorescence (BGYF) on pistachio nuts and cashews. Previous researchers established that the presence of BGYF indicates that there is a high probability of aflatoxin contamination. Since BGYF is not a definitive indicator of aflatoxin contamination, samples emitting fluorescence should be removed and tested for aflatoxins by chemical means. This study, conducted in a static way, is an important step towards the development of a new more accurate and automatic aflatoxin screening method based on a vision system. In this work, a total of 352 samples of pistachio nuts and cashews were evaluated, half of which came from lots contaminated with aflatoxin. Two images in the 410–600 nm optical range were acquired for each sample. Imaging algorithms were developed to identify samples with fluorescent stains caused by BGYF. According to the image analysis results, nut samples were classified into two groups: fluorescent stains (FS) and non-fluorescent stains. Both BGYF and non-fluorescent samples were analyzed for aflatoxin. The laboratory analysis results showed a high correlation with the camera classification: pistachios and cashews placed in the FS group by the vision system contained 92 % and 82 % of the total number of nuts contaminated with aflatoxin, respectively. Moreover, a discriminant analysis of reflectance data was carried out in order to select the optimal optical range to detect BGYF, both in pistachio nuts, i.e., 480 and 520 nm, and in cashews, i.e., 440 and 600 nm.     

Effect of selected mould strains on lipolysis in dry fermented sausages

 Several batches of fermented sausages were prepared and inoculated with five strains of moulds belonging to the genera Penicillium and Mucor, selected for their enzymatic activity, and a strain of Penicillium nalgiovense obtained as a commercial starter culture. Control batches were manufactured similary, but without inoculation. Sausages were produced with either artificial or natural casings, and very similar results were obtained with both. The evolution of the different lipidic fractions was monitored, paying special attention to the free fatty acid (FFA) fraction. Two strains presented a high lipolytic activity as indicated by the rise in FFA in comparison to control batches. In conclusion, not all the mould strains contributed to the lipolytic process occurring during sausage ripening and, therefore, not all of these had a positive effect on the final quality of the product. If moulds are to be used for this purpose it is, therefore, necessary to carefully select suitable moulds beforehand. Received: 25 September 1998 / Revised version: 4 February 1999     

春草莓表面霉菌鉴定及其致腐能力研究

目的调查春草莓表面霉菌的总体状况,对主要致腐真菌进行致腐能力和产毒素研究,为草莓的保鲜及食用安全评价提供理论依据。方法对60份春草莓样品进行霉菌检测,分离霉菌采用ITS序列测序方法进行鉴定;利用高效液相色谱法及酶联免疫法对腐烂草莓及真菌发酵液中赭曲霉毒素A(ochratoxin A,OTA)和展青霉素(patulin,PAT)进行检测,对出现率较高的霉菌进行草莓复接试验,判断其致腐能力。结果健康草莓表面的霉菌计数对数值3.5~5.5的占样品总数的83%;毛霉菌属、枝孢菌属和青霉菌属在草莓中出现率较高;由这3类霉菌致草莓腐烂样品和其发酵液均检测不出真菌毒素OTA和PAT,复接试验中毛霉属真菌在36 h在草莓表面形成明显菌斑,72 h可形成明显菌斑而更大面积软腐。结论草莓表面存在大量且多种霉菌,霉菌侵染草莓是导致其腐烂主要诱因,毛霉属霉菌占主要生态位但青霉菌属、枝孢菌属霉菌更易导致其软腐,草莓表面霉菌不会产生真菌毒素而对草莓进行二次污染。     

Mycological condition of maize products.

Maize and maize-related products were investigated in a collaborative study for viable moulds and antigenic extracellular polysaccharides (EPS) produced by Aspergillus and Penicillium species. In addition, the samples were tested for the presence of aflatoxin B1. All maize products, with the exception of the heat processed products, contained viable moulds on an average of (log10 values) 3.3 +/- 0.7 colony-forming units per gram. In most samples a mixed mould flora was present. Species of the genus Fusarium were dominant, followed by Aspergillus, Eurotium and Penicillium. The mould colony count correlated positively with the presence of antigenic extracellular polysaccharides produced by species of Aspergillus and Penicillium. Gamma irradiation did not affect the detection of antigenic extracellular polysaccharides. Aflatoxin B1 was detected in two out of 35 samples; these contained 0.6 and 0.8 microgram/kg. From one of these aflatoxin B1-containing samples, Aspergillus flavus was isolated.     

Chicken fillets subjected to UV‐C and pulsed UV light: Reduction of pathogenic and spoilage bacteria,and changes in sensory quality

We have compared the efficacy of continuous ultraviolet (UV‐C) (254 nm) and pulsed UV light in reducing the viability of Salmonella Enteritidis, Listeria monocytogenes, Staphylococcus aureus, enterohemorrhagic Escherichia coli, Pseudomonas spp., Brochothrix thermospacta, Carnobacterium divergens, and extended‐spectrum β‐lactamase producing E. coli inoculated on chicken fillet surface. Fluences from 0.05 to 3.0 J/cm² (10 mW/cm², from 5 to 300 s) used for UV‐C light resulted in average reductions from 1.1 to 2.8 log cfu/cm². For pulsed UV light, fluences from 1.25 to 18.0 J/cm² gave average reductions from 0.9 to 3.0 log cfu/cm². A small change in the odor characterized as sunburnt and increased concentration of volatile compounds associated with burnt odor posed restrictions on the upper limit of UV treatment, however no sensory changes were observed after cooking the meat. Treatments under modified atmosphere conditions using a UV permeable top film gave similar or slightly lower bacterial reductions.

Practical applications

Ultraviolet (UV) light may be used for decontaminating the surface of food products and reduce viability of pathogenic and spoilage bacteria. Exposure of raw chicken fillet surface to various doses of continuous UV‐C or pulsed UV light proposed in the present work represent alternatives for microbiological improvement of this product. Chicken fillets can be treated in intact packages covered with UV permeable top film, thus avoiding recontamination of the meat. UV‐C light treatment is a low cost strategy with low maintenance, whereas pulsed UV light involves more elaborate equipment, but treatment times are short and less space is required. Both methods can be helpful for producers to manage the safety and quality of chicken fillets.     

Mycoflora and natural occurrence of aflatoxin,cyclopiazonic acid,fumonisin and ochratoxin A in dried figs

Mycoflora, the mycotoxigenic properties of moulds, and natural contamination with mycotoxins such as aflatoxins (AFs), cyclopiazonic acid (CPA), fumonisin B₁ (FB₁) and ochratoxin A (OTA) were investigated in dried figs. Dry fig samples were collected from orchards during the drying stage in the Aegean Region of Turkey. Fungal isolates were identified using morphological, chemical as well as molecular methods. Mycotoxigenic characteristics of moulds were assessed by thin-layer chromatography (TLC) and high-performance liquid chromatography (HPLC). Mycotoxins except CPA (by TLC) were determined by HPLC. All the fig samples were contaminated with moulds and 94.7% contained one or more mycotoxigenic species. The most prevalent moulds present in dried figs belong to the Aspergillus section Nigri members, being 93.9% positive for the samples, followed by Fusarium spp., Aspergillus section Flavi and Penicillium spp. On the other hand, Fusarium spp. had the highest count and the number of fumonisin producing Fusarium was also high. A total of 48% of 115 dried fig samples contained OTA (range?=?0.1–15.3?ng?g^?1), 74.7% of the samples had FB₁ (range?=?0.05–3.65?mg?kg^?1), 10.0% of the samples had aflatoxin (range?=?0.1–763.2?ng?g^?1) and 24.3% of the samples were tentatively identified as being contaminated with CPA (range?=?25–187?ng?g^?1). Dried fig samples were contaminated with one (33.0%), two (47.0%), three (5.2%) and four mycotoxins (3.5%). A total of 11.3% of dried fig samples were not contaminated with any of the four mycotoxins. To the best of our knowledge, CPA and fumonisin have been found for the first time in dried figs.