Citrinin-producing capacity of Penicillium expansum strains from apple packinghouses of Lerida (Spain)

Multifunctional chitosan/grape seed extract/silver nanoparticle composite for food packaging application

Food-borne fungi present significant hazards to food preservation and human health. Oxidation causes spoilage and the inedibility of the fruit. However, traditional packaging films without antimicrobial or antioxidant activities do not satisfy the active packaging requirements. Films with antimicrobial and antioxidant activities are urgently required. In this study, silver nanoparticles (AgNPs) were synthesized from fruit waste grape seed extracts (GSE). The antimicrobial and antioxidant activities of GSE-silver nanoparticles (GSE-AgNPs) and AgNPs (average size 20 nm) stabilized by polyvinyl pyrrolidone (PVP-AgNPs) were evaluated in vitro. The effect of chitosan (CS)-coated GSE-AgNPs and PVP-AgNPs on the postharvest quality of grape was studied during storage at 20 °C for 5 days. The results confirmed that grapes treated with CS and GSE-AgNPs showed significantly reduced decay percentage, weight loss, and maintained titratable acidity at high levels compared with those of untreated fruit and fruit treated with PVP-AgNPs. Moreover, CS and GSE-AgNPs significantly inhibited the total mold count during storage. Our results suggest that CS coating enriched with GSE-AgNPs has the potential to preserve the quality and extend the shelf life of grapes.

Investigation of patulin and citrinin in grape must and wine from grapes naturally contaminated by strains of Penicillium expansum

Twenty three strains of Penicillium expansum, as a predominant species, were isolated from 23 (92%) out of 25 grape samples of 17 different grape varieties. The results of the identification of P. expansum strains were confirmed by a PCR method. Most of the isolates of P. expansum (21/23, 91%), when tested for toxigenicity, were bi-toxigenic: they produced citrinin (CIT) and particularly high amounts of patulin (PAT). A validated UPLC-MS/MS method for the determination of PAT and CIT was applied. The limits of quantification (LOQ) for PAT and CIT in grape must and toxigenicity testing samples were 100 and 2 ng/g, respectively. The results of PAT and CIT quantification in 23 grape must samples demonstrated the occurrence of PAT in 10 (43%) grape must samples (mean: 171 ng/g; median: 50 ng/g; and range: 143-644 ng/g) and the occurrence of CIT in two (9%) grape must samples (mean: 1 ng/g; median: 1 ng/g; and range: 2.5-3.5 ng/g). This is the first report on the natural occurrence of CIT in grape must. A validated HPLC-UV-VIS method for the determination of PAT in wine samples was applied, and concentrations in all 23 wine samples were below the LOQ (<10 ng/g).

Oxidative stress induces the biosynthesis of citrinin by Penicillium verrucosum at the expense of ochratoxin

Penicillium verrucosum is a fungus that can produce ochratoxin A and citrinin, two structurally related nephrotoxic mycotoxins. P. verrucosum usually occurs on wheat but can occasionally also be found in NaCl rich habitats such as salted cheeses or olives, indicating that this fungus can adapt to different environments. The ratio of ochratoxin A to citrinin produced by P. verrucosum is shifted to one of either mycotoxin at the expense of the other dependent on the environmental conditions. High NaCl concentrations shift secondary metabolite biosynthesis towards ochratoxin A production. P. verrucosum copes with NaCl stress by increased ochratoxin A biosynthesis, ensuring chloride homeostasis. Ochratoxin A carries chlorine in its molecule and can excrete chlorine from the cell. It was further shown that the regulation of ochratoxin A by high NaCl conditions is mediated by the HOG MAP kinase signal transduction pathway. Here it is shown that high oxidative stress conditions, evoked for example by increasing concentrations of Cu(2+) cations in the growth medium, shift secondary metabolite biosynthesis of P. verrucosum from ochratoxin A to citrinin. The production of citrinin normalizes the oxidative status of the fungal cell under oxidative stress conditions leading to an adaptation to these environmental conditions and protects against increased oxidative stress caused by increased Cu(2+) concentrations. Moreover citrinin also protects against light of short wavelength, which may also increase the oxidative status of the environment. The biosynthesis of citrinin is apparently regulated by a cAMP/PKA signaling pathway, because increasing amounts of external cAMP reduce citrinin biosynthesis in a concentration dependent manner. These conditions lead to the cross-regulation of the ochratoxin A/citrinin secondary metabolite pair and support the adaptation of P. verrucosum to different environments.

Production of lipase free of citrinin by Penicillium citrinum

Lipase (Glycerol ester hydrolase E.G. 3.1.1.3) from a Brazilian strain of Penicillium citrinum free of the mycotoxin citrinin has been investigated. Citrinin production was inhibited by using culture medium containing olive oil, soybean oil and corn oil as carbon sources. Potassium concentration and pH play an important role in citrinin production. Potassium concentration lower than 30 mM and pH below 4.5 inhibited the mycotoxin production. P. citrinum produced lipase free of extraneous proteins and citrinin when cultured using, as nitrogen source, ammonium sulphate (lipase activity of 7.88 U/mg) and yeast extract (lipase activity of 4.95 U/mg) with olive oil as carbon source. This data is relevant to the larger scale production of lipases for food technology applications, from Penicillium citrinum.

Contamination by moulds of grape berries in Slovakia

This paper describes the first map, albeit partial, of toxigenic fungi re-isolated from grape berries collected in three out of the six most important Slovakia winemaking areas in two different periods of the harvest year 2008. Low temperatures and high relative humidity during July 2008 favoured the development of grape fungal diseases that cause rots such as Plasmopara, Uncinula, Botrytis, Metasphaeria, Elsinoë, and Saccharomycetes. In the analysed samples, the following genera of toxigenic fungi were identified in the range of 1-4%: Aspergillus, Alternaria, Cladosporium, Epicoccum, Fusarium, Penicillium, Rhizopus, Ulocladium, and Trichoderma Trichothecium, while the genera Aspergillus, Alternaria, Fusarium, and Penicillium were in the range 11-29%. A. niger, A. carbonarius, some strains of A. carbonarius-with 'crystals' and strains of A. uvarum-uniseriate were identified; these species are considered ochratoxigenic (able to produce variable amounts of toxins). In addition, a non-ochratoxigenic strain of A. ibericus and a Fusarium strain able to biosynthesize small amount of fumonisins, beauvericin, and enniatins were identified. P. expansum, able to produce citrinin, represents 29.7%, of the Penicillium genus together with P. verrucosum, P. glabrum, P. citrinum, and P. crustosum. An analysis for the identification and quantification of the main toxins: ochratoxin A, fumonisins, beauvericin, enniatins, and fusaproliferin was performed on grape samples; it was consistent with the results of the mycological analysis. Toxigenic fungi should be checked throughout the years and their occurrence compared with all environmental factors to avoid health risks.

Production of mycotoxins by Penicillium expansum inoculated into apples

We investigated the production of mycotoxins in apple fruits inoculated with spores of 40 strains of apple blue mold, Penicillium expansum. Patulin and citrinin contents in the extracts from apples stored at 25 degrees C for 12 days after inoculation were determined by high-performance liquid chromatography (HPLC) analysis with UV and fluorescence detection. Patulin and citrinin were produced by 90% (36) and 80% (32) of the 40 strains, indicating that P. expansum is a consistent producer of these mycotoxins. The patulin content in the extracts was substantially higher than the citrinin content. Other mycotoxins whose production in pure culture has been reported were simultaneously detected with high-resolution liquid chromatography-mass spectrometry (LC-MS) analysis with the positive ion mode of electrospray ionization. Along with patulin and citrinin, expansolides A and B were identified based on the HPLC and LC-MS spectral data and detected in 88% (35) of the extracts. The results indicate that P. expansum is a consistent producer of expansolides A and B in rotten areas of apple fruits. The findings raise the possibility that products from decayed apples might contain expansolides A and B in addition to patulin and citrinin.

Penicillium expansum: consistent production of patulin, chaetoglobosins, and other secondary metabolites in culture and their natural occurrence in fruit products

Penicillium expansum is known for its destructive rot and patulin production in apple juice. According to the literature, P. expansum can, among other compounds, produce citrinin, ochratoxin A, patulin, penitrem A, and rubratoxin B. In this study the qualitative production of metabolites was examined using TLC (260 isolates), HPLC (85 isolates), and MS (22 isolates). The results showed that none of the 260 isolates produced ochratoxin A, penitrem A, or rubratoxin B. However, chaetoglobosin A and communesin B were produced consistently by all 260 isolates. Patulin and roquefortine C were produced by 98% of the isolates. Expansolides A/B and citrinin were detected in 91 and 85% of the isolates, respectively. Chaetoglobosins and communesins were detected in naturally infected juices and potato pulp, whereas neither patulin nor citrinin was found. Because most P. expansum isolates produce patulin, citrinin, chaetoglobosins, communesins, roquefortine C, and expansolides A and B, foods contaminated with this fungus should ideally be examined for chaetoglobosin A as well as patulin.

Mycotoxins in fruits, fruit juices, and dried fruits

This review gives an overview of the presence of mycotoxins in fruits. Although several mycotoxins occur in nature, very few (aflatoxins, ochratoxin A, patulin, Alternaria toxins) are regularly found in fruits. It has been shown that the presence of fungi on fruits is not necessarily associated with mycotoxin contamination. The formation of mycotoxins depends more on endogenous and environmental factors than fungal growth does. Mycotoxins may remain in fruits even when the fungal mycelium has been removed. Depending on the fruit and the mycotoxin, the diffusion of mycotoxins into the sound tissues of fruits may occur. The influence of the selection and storage of fruits and the influence of different processing steps involved in the production of fruit juices and dried fruits on possible mycotoxin contamination is described. It is shown that the careful selection, washing, and sorting of fruits is the most important factor in the reduction of mycotoxin contamination during the production of fruit juices. The processing of fruits does not result in the complete removal of mycotoxins.

Co-occurrence of patulin and citrinin in Portuguese apples with rotten spots

Patulin and citrinin are mycotoxins produced by certain fungi mainly belonging to Penicillium and Aspergillus and may be detected in mouldy fruits and fruit products. The data presented here refer to the simultaneous occurrence of patulin and citrinin in 351 samples of seven different varieties of apples with small rotten areas (Casanova, Golden Delicious, Red Delicious, Reineta, Richared, Rome Beauty, Starking). A rapid multidetection thin layer chromatography (TLC) method was used. The minimum detectable concentrations of patulin and citrinin were 120-130 and 15-20 microg kg(-1) respectively. The percentage contamination with patulin only was higher (68.6%) than that with citrinin only (3.9%). Patulin and citrinin (19.6%) were also detected simultaneously. The highest mean patulin content was 80.50 mg kg(-1) for the Richared variety, but the mean level of citrinin was lower. The lowest mean contaminations of patulin were found in Rome Beauty, Red Delicious and Reineta, ranging from 3.06 to 5.37 mg kg(-1). All analysed apples varieties had low citrinin contamination, ranging from 0.32 to 0.92 mg kg(-1). These findings indicate that there may be a risk of human exposure to patulin through the consumption of juices and jams manufactured with apples with small rotten areas.

Mycotoxin production by Penicillium expansum on blackcurrant and cherry juice

The production of mycotoxins and other secondary metabolites by Penicillium expansum on blackcurrant and cherry juice has been studied at 10 degrees C and 25 degrees C under storage imitated conditions. P. expansum was able to synthesize extracellular patulin under all conditions, and together with extracellular chaetoglobosin A when unlimited oxygen was available. Patulin, the chaetoglobosins A and C, the communesins A and B and the expansolides A and B could be detected intracellularly depending on the conditions. The metabolites were detected using thin-layer chromatography and high-performance liquid chromatography with diode array detection by comparison to standards. A method to detect the expansolides A and B by TLC was developed.

Mechanism of citrinin-induced dysfunction of mitochondria. V. Effect on the homeostasis of the reactive oxygen species

The effects of citrinin in the maintenance of the homeostasis of the reactive oxygen species in rat liver cells were evaluated. Citrinin (CTN) modifies the antioxidant enzymatic defences of cells through the inhibition of GSSG-reductase and transhydrogenase. No effect was observed on GSH-peroxidase, catalase, glucose 6-phosphate and 6 phosphogluconate dehydrogenases, and superoxide dismutase. The mycotoxin increased the generation of reactive oxygen species, stimulating the production of the superoxide anion in the respiratory chain. The results suggest that oxidative stress is an important mechanism, side by side with other effects previously shown, in the establishment of the cytotoxicity and cellular death provoked by CTN in several tissues.

Moulds in food spoilage

There is an increasing knowledge and understanding of the role played by moulds in food spoilage. Especially the discovery of mycotoxin production in foods has highlighted the importance of moulds in food quality. It is, however, only within the last 5-10 years that major progresses have been made towards the prevention of spoilage caused by moulds. This is due to recent international agreements on taxonomy and analytical methods for foodborne moulds, which has led to the discovery, that a specific, very limited funga (= mycobiota) is responsible for the spoilage of each kind of food. This is called the associated or critical funga and has been shown to consist of less than ten species. In this paper the associated funga is described for the following foods: citrus and pomaceous fruit, potato and yam tubers, onions, rye, wheat, rye bread, cheese and fermented sausage and whenever possible the selective principle of the food is discussed. In the description only references which are using the new taxonomy and mycological methods have been used. The individual fungas are very different from each other, which again means that the potential appearance of a specific mycotoxin is restricted to a limited number of foods. The important mycotoxin pattern of each food is described including toxins which originate from 'carry over'. For some foods examples are also given on spoilage of sensoric properties due to moulds. Finally, preventive action against the growth of the associated funga is described for some of the foods and it is concluded that optimization of the prevention and control of moulds in foods must be based on knowledge of the associated funga.