Search

Aims: To evaluate the effect of Botrytis cinerea growth on ochratoxin A (OTA) production by Aspergillus carbonarius and degradation. Methods and Results: OTA-producing A. carbonarius and B. cinerea were grown on grape-like medium at 20°C for 7 days. Radii of colonies were daily recorded and OTA was analysed. In addition, each B. cinerea isolate was inoculated on grape-like synthetic nutrient medium (SNM) paired with each A. carbonarius isolate at a distance of 45 mm. Botrytis cinerea isolates were also grown in OTA-spiked SNM. Growth rates of B. cinerea and A. carbonarius were 20 and 7·5 mm day−1, respectively. The growth of the colonies of each species stopped when they contacted each other in paired cultures. OTA production by A. carbonarius in the contact area was affected by B. cinerea, but no clear trend was observed. All B. cinerea isolates showed to degrade between 24·2% and 26·7% of OTA from spiked SNM. Conclusions: The ecological advantage of B. cinerea, in terms of growth rate, vs. OTA-producing Aspergillus in some wine-growing regions and its ability to degrade OTA may explain the low levels of this toxin in noble wines. Significance and Impact of the Study: At determinate conditions, the presence of B. cinerea in grapes with A. carbonarius may help in reducing OTA accumulation. [ABSTRACT FROM AUTHOR]

Aims: To evaluate the impact of modified atmosphere packaging on in vitro growth of Aspergillus carbonarius and Aspergillus niger, and possible effects on ochratoxin A (OTA) biosynthesis. Methods and Results: Ochratoxigenic isolates belonging to the species A. carbonarius and A. niger were grown on a synthetic grapejuice medium (SNM) and packaged in combinations of controlled O2 (1% and 5%) and CO2 levels (0% and 15%), and in air as a control. Colony diameters were recorded every 3 days up to 21 days, and OTA was analysed after 7, 14 and 21 days. The greatest reductions in mycelial growth rate were observed at 1% O2 followed by 1% O2/15% CO2, whereas 5% O2 stimulated the growth of all isolates. OTA production by A. carbonarius and A. niger isolates was minimized at 1% O2/15% CO2 and 1% O2, respectively, after 7 days of incubation. Maximal OTA accumulation after 7 days was observed for all isolates in the control pack and at 5% O2. Conclusions: Of the atmospheres tested, only 1% O2 combined with 15% CO2 consistently reduced fungal growth and OTA synthesis by A. carbonarius and A. niger. Significance and Impact of the Study: Storage under modified atmospheres is unlikely to be suitable as the sole method for OTA minimization and grape preservation; other inhibitory factors are necessary. [ABSTRACT FROM AUTHOR]

Aims: To examine how UVC affects the different genera of fungi commonly isolated from grapes, with the aim of understanding changes in mycobiota during grape ripening and possible applications for preventing grape decay during storage. Methods and Results: Spores of Aspergillus carbonarius, Aspergillus niger, Cladosporium herbarum, Penicillium janthinellum and Alternaria alternata (between 100–250 spores/plate agar) were UVC irradiated for 0 (control), 10, 20, 30, 60, 300 and 600 s. Plates were incubated at 25°C and colonies were counted daily up to 7 days. Alternaria alternata and Aspergillus carbonarius were the most resistant fungi. Conidial germination in these species was reduced by approx. 25% after 10 s of exposure, compared with greater than 70% reduction for the remaining species tested. Penicillium janthinellum spores were the most susceptible at this wavelength. UVC exposures of 300 s prevented growth of all isolates studied, except for Alternaria alternata. Conclusions: UVC irradiation plays a major role in selecting for particular fungi that dominate the mycobiota of drying grapes. Significance and Impact of the Study: The UVC irradiation of harvested grapes could prevent germination of contaminant fungi during storage or further dehydration. [ABSTRACT FROM AUTHOR]

Aims: To evaluate the effect of preharvest grape pesticides in Aspergillus section Nigri infection in dehydrating grapes and the final ochratoxin A (OTA) content. Additionally, the effect of coinoculation of moulds frequently isolated from grapes and raisins on Aspergillus section Nigri infection was studied. Methods and Results: Fungicide-treated grapes were inoculated with Aspergillus carbonarius, Aspergillus niger aggregate, Eurotium amstelodami and Penicillium janthinellum in different combinations, then dehydrated by reducing aw for 20 days. The percentages of colonized grapes treated with fungicides were, in general, lower, but no differences were observed among fungicides. The untreated grapes always showed higher concentrations of OTA, regardless of the inoculum applied. In general, Chorus was the most effective antifungal treatment in reducing OTA accumulation in grapes during dehydration. Penicillium janthinellum reduced Aspergillus section Nigri colonization and OTA accumulation in grapes during dehydration. Conclusions: The four preharvest fungicides studied reduced the Aspergillus section Nigri growth and OTA production by A. carbonarius during dehydration of grapes. Significance and Impact of the Study: The success of these chemical treatments might depend on the mycobiota composition of grapes. [ABSTRACT FROM AUTHOR]

Aims: To test the ability of Fusarium proliferatum strains isolated from Pinus pinea to synthesize fumonisin B1 (FB1) in pine nuts. Method and Results: Eleven strains were inoculated in moist sterile shelled pine nuts and whole pine nuts, and incubated for 28 days. Moist sterile maize was inoculated in parallel as an optimum substrate for FB1 production by Fusarium species. Conclusions: Six of the strains produced FB1 in shelled pine nuts, and two of them did so in whole pine nuts. Impact and Significance of the Study: F. proliferatum is able to grow and produce FB1 in the husk of pine nuts and the mycotoxin can be found in the nut once shelled. Consequently, FB1 may be an important hazard in pine nuts. [ABSTRACT FROM AUTHOR]

Aims: The aim of this study was to assess the opportunities of Penicillium expansum to develop and produce patulin in apples during cold storage and in the steps prior to processing of apple products. Methods and Results: Two lots of apples var. Golden with different ripeness degree were used. Half of each lot was fungicide treated. Apples were inoculated with P. expansum and stored at 1°C for 6 weeks. The extent of lesions and patulin accumulation both at the end of cold storage and after 3 days at 20°C were assessed. Short storage at 20°C aimed to simulate the transport and storage steps at room temperature before processing. Lesion size significantly increased during the storage at 20°C. An interaction between fungicide treatment and ripeness degree was found; efficiency of fungicide treatment was higher for ripe apples. Although lesions were evident after cold storage, no patulin was detected. Patulin was detected only when fruits were further stored at 20°C. Neither ripeness degree nor fungicide treatment affected patulin accumulation. Conclusions: Cold storage periods of 6 weeks do not lead to patulin accumulation. Significance and Impact of the Study: Shortening preprocessing times at warm temperatures would result into a reduction in patulin content at initial steps of fruits entering the processing plants. [ABSTRACT FROM AUTHOR]

a. valero, s. marín, a.j. ramos and v. sanchis. 2005. To explain the dominance of OTA-producing fungal species in sun-dried grapes for special wine production through an ecophysiological approach. Grapes at different ripening stages, sun-dried grapes and raisins were analysed for fungal presence, and isolates identified. Aspergillus section Nigri incidence in grapes increased with grape maturation. In the ecophysiological study five isolates ( Alternaria alternata, Cladosporium herbarum, Penicillium decumbens, Aspergillus carbonarius, A. niger aggregate and A. section Nigri uniseriate) were inoculated in SNM medium at four aw (0·82–0·97) and incubated at 20, 30 and 40°C for 18 d. Isolates were also inoculated in pairs to evaluate fungal interactions recording their growth rates and indexes of dominance. Aspergillus section Nigri grew in a wider range of temperature and aw, had higher growth rates than the others under most of the conditions tested and showed behaviour usually dominant. The presence of A. section Nigri is predominant in grapes during harvesting and sun-drying period likely because of a better adaptation to hot and humid environment. The duration of the drying period should be reduced as much as possible without compromising the quality of the final product, or drying the grapes in controlled chambers with dry hot air flow. [ABSTRACT FROM AUTHOR]

n. bellí, a.j. ramos, i. coronas, v. sanchis and s. marín. 2005.The effects of water activity (0·90–0·99aw), temperature (15–37°C), and their interaction on growth and ochratoxin A (OTA) production by eight isolates ofAspergillus carbonariuswere investigated on synthetic nutrient medium (SNM) with composition similar to grapes.Growth data were modelled by an multiple linear regression and response surface models were obtained.Aspergillus carbonariusgrew much faster at 30°C than at the other temperature levels tested and its growth rate increased with increasingaw, maximum growth rate being between 0·95 and 0·99aw. In general, isolates grew faster at 35–37°C than at 20°C, although no significant differences were found between these temperatures. OTA accumulation was also favoured by highaw levels, and although it was observed in the whole range of temperatures, maximum amounts were detected at 20°C. No OTA was found at the most unfavourable growth conditions.Optimumaw level for growth seems to correspond with optimum for OTA production, meanwhile the most propitious temperature for the toxin production was below the best one for growth.Prediction ofA. carbonariusgrowth would allow estimating their presence and therefore, the OTA production, as it was found that conditions for the toxin production were more limited than those permitting growth. [ABSTRACT FROM AUTHOR]

a. velluti, v. sanchis, a.j. ramos, c. turon and s. marín. 2004. The effect of five essential oils (oregano, cinnamon, lemongrass, clove and palmarose) on growth rate, zearalenone (ZEA) and deoxynivalenol (DON) production by Fusarium graminearum strains was assessed. The influence of the essential oils was tested on irradiated maize at two concentrations (500 and 1000 mg kg−1), at different water activity ( aw) (0·95 and 0·995) and temperature (20 and 30°C) levels. At 0·995 aw all essential oils tested had an inhibitory effect on growth rate of F. graminearum at both temperatures studied. At this aw level, DON production in general was inhibited by all essential oils at 30°C and, although palmarose and clove were the only essential oils with statistically significant inhibitory effect on ZEA production, an inhibitory trend was observed when cinnamon and oregano oils were added to maize grain. Antifungal and antimycotoxigenic activity of the essential oils assayed was shown to depend on environmental conditions. It is apparent that essential oils should be considered as alternative preharvest natural fungicides. Further investigation on natural maize grain might be useful to study the effectiveness of these essential oils in the presence of natural mycoflora of maize grain. [ABSTRACT FROM AUTHOR]

n. bellí, a.j. ramos, v. sanchis and s. marín. 2003. The objective of this study was to determine the temporal ochratoxin A (OTA) accumulation profile of Aspergillus section Nigri at different water activity ( aw) levels. Two Aspergillus carbonarius and two Aspergillus niger aggregate strains isolated from grapes were tested in vitro for OTA accumulation at 25°C on synthetic nutrient medium, over periods of 20 days at different aw levels. Results were modelled by a multiple linear regression and response surface predictive models were obtained. High levels of aw favoured OTA production by these moulds. Maximum amounts of OTA were found at the earlier growth states (5 days for A. carbonarius and 7–13 days for A. niger aggregate). Provided that A. section Nigri, and mainly A. carbonarius, play the main role in OTA presence in grapes, it would be critical to adjust the harvest and processing time to significantly reduce the chances for OTA accumulation. Ochratoxin A production by A. section Nigri has been shown for the first time to occur optimally after as little as 5 days on a grape-like medium. [ABSTRACT FROM AUTHOR]

Abstract Aims: To investigate the volatile fractions of 16 essential oils for activity against the more common fungi causing spoilage of bakery products, Eurotium amstelodami , E. herbariorum , E. repens , E. rubrum , Aspergillus flavus , A. niger and Penicillium corylophilum . Methods and Results: The study applied 50 μ l of pure essential oils in a sterilized filter paper, were carried out at pH 6 and at different water activity levels (0·80–0·90). First, a wheat flour based agar medium was used, where cinnamon leaf, clove, bay, lemongrass and thyme essential oils where found to totally inhibit all microorganisms tested. These five essential oils were then tested in sponge cake analogues, but the antifungal activity detected was much more limited. Conclusion: Five essential oils showed potential antifungal capacity against all species tested, over a wide range of water availability. Their activity, however, seems to be substrate-dependent. More research is needed to make them work in real bakery products, as in the preliminary study limited effectiveness was found. Significance and Impact of the Study: The potential of the cinnamon leaf, clove, bay, lemongrass and thyme essential oils against species belonging to Eurotium, Aspergillus and Penicillium genus has been demonstrated. [ABSTRACT FROM AUTHOR]