The aim of this study was to investigate in vitro and model the effect of temperature (T) and water activity (aw) conditions on growth and toxin production by some toxigenic fungi signaled in cheese. Aspergillus versicolor, Penicillium camemberti, P. citrinum, P. crustosum, P. nalgiovense, P. nordicum, P. roqueforti, P. verrucosum were considered they were grown under different T (0–40 °C) and aw (0.78–0.99) regimes. The highest relative growth occurred around 25 °C; all the fungi were very susceptible to aw and 0.99 was optimal for almost all species (except for A. versicolor, awopt = 0.96). The highest toxin production occurred between 15 and 25 °C and 0.96–0.99 aw. Therefore, during grana cheese ripening, managed between 15 and 22 °C, ochratoxin A (OTA), penitrem A (PA), roquefortine-C (ROQ-C) and mycophenolic acid (MPA) are apparently at the highest production risk. Bete and logistic function described fungal growth under different T and aw regimes well, respectively. Bete function described also STC, PA, ROQ-C and OTA production as well as function of T. These models would be very useful as starting point to develop a mechanistic model to predict fungal growth and toxin production during cheese ripening and to help advising the most proper setting of environmental factors to minimize the contamination risk.

The present work aimed to contribute information on the mycobiota associated with ripening grana cheese, with focus on the genus Penicillium as potential mycotoxin producers. Eighteen wheels of grana cheese, aged in different storehouses situated in Northern Italy, were sampled to isolate associated fungi. Penicillium spp. were commonly dominant; morphological observation and gene sequencing were applied to identify Penicillium at species level. P. crustosum and P. solitum were the dominant species. Citrinin and ochratoxin A mycotoxins were analysed and the latter was found in all grana cheese samples. These results confirmed that a polyphasic approach is mandatory for Penicillium identification at species level.

Penicillium and Aspergillus genera, both including mycotoxin producing species, were reported as associated to cheese and cheese working environment, but never studied in an extensive way in Italian grana cheese (Grana Padano and Parmigiano Reggiano). The aim of this work was to address the identification of Aspergilli and Penicillia associated to grana cheese in order to lay down the basis for risk assessment and safe processing for a high quality production. One hundred and four strains belonging to Aspergillus and Penicillium genera were obtained from cheese crust and from ripening room air (with the latter largely dominant), and identified following a polyphasic approach, strongly required for the identification at the species level. Morphological observation was used along with molecular techniques, RAPD-PCR fingerprinting and calmodulin gene sequencing (CaM), the former aimed to limit as much as possible the latter sequencing effort. Seventy four percent of the strains were assigned to Penicillium subgenus Penicillium, section Fasciculata. Main mycotoxin producing species identified were A. flavus, P. crustosum and P. verrucosum, while the dominant species in both air and cheese crust was P. solitum, which has never been so far reported as mycotoxigenic. Results obtained in this study confirmed that mycotoxin contamination is a possible issue to face during grana cheese making.

No abstract

The aim of this work was to study the dynamic profile of mycotoxin producing fungi as well as the accumulation of free and hidden fumonisins along the maize chain. Raw maize was sampled at harvest, at the storehouse and after drying. The study continued on the dried maize bulk along the storage period in a commercial silo, which was sampled during discharge at 6, 7, 8 and 10 months. Finally, the flour obtained after kernel milling and corresponding to the silo discharges was investigated. The sampling approach, designed in agreement with EU regulations and tested for reliability, was used along the maize chain, obtaining very good results. The prevalent fungi found in maize kernels belonged to Fusarium section Liseola. Comparable results, in terms of both fungal incidence and fumonisin contamination, were obtained for the samples collected at harvest and at the storehouse, opening the possibility to adapt the maize chain monitoring to the needs of the farmer/enterprise. A reduction in fungal colony forming units was noticed after drying, supposedly due to the thermal treatment. Very similar amounts of free and hidden fumonisins were detected in raw maize and after drying, confirming the reliability of the sampling approach. During silo storage, up till to 10 months, a significant decrease was recorded for both free and hidden fumonisins. A significant increase in the free-to-total fumonisin ratio was observed moving from stored kernels to commercial flour, suggesting that milling leads to a reduction of the masked fraction. This result, together with the increase of free fumonisins after maize drying, should be considered in future studies. Especially the effect of drying conditions and milling treatments on the fumonisin masking phenomena should be further investigated.