Debaryomyces hansenii strains differ in their production of flavor compounds in a cheese-surface model.

Flavor production among 12 strains of Debaryomyces hansenii when grown on a simple cheese model mimicking a cheese surface was investigated by dynamic headspace sampling followed by gas chromatography-mass spectrometry. The present study confirmed that D. hansenii possess the ability to produce important cheese flavor compounds, primarily branched-chain aldehydes and alcohols, and thus important for the final cheese flavor. Quantification of representative aldehydes (2-Methylpropanal, 3-Methylbutanal) and alcohols (2-Methyl-1-propanol, 3-Methyl-1-butanol, and 3-Methyl-3-buten-1-ol) showed that the investigated D. hansenii strains varied significantly with respect to production of these flavor compounds. Contrary to the alcohols (2-Methyl-1-propanol, 3-Methyl-1-butanol, and 3-Methyl-3-buten-1-ol), the aldehydes (2-Methylpropanal, 3-Methylbutanal) were produced by the D. hansenii strains in concentrations higher than their sensory threshold values, and thus seemed more important than alcohols for cheese flavor. These results show that D. hansenii strains may have potential to be applied as cultures for increasing the nutty/malty flavor of cheese due to their production of aldehydes. However, due to large strain variations, production of flavor compounds has to be taken into consideration for selection of D. hansenii strains as starter cultures for cheese production.

Simultaneous determination of ochratoxin A, mycophenolic acid and fumonisin B(2) in meat products.

Here we present a method for simultaneous determination of the fungal metabolites mycophenolic acid, ochratoxin A (OTA) and fumonisin B(2) (FB(2)) in meat products. Extraction was performed with water-acetonitrile, followed by acetone-induced precipitation of salts and proteins. Purification and identification of analytes was performed by mixed-mode reversed-phase anion-exchange chromatography in direct ion-exchange mode, followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) detection. Quantification was based on isotope dilution with fully (13)C-labelled FB(2) and OTA, and matrix-spiked calibration curves. Fermented sausages inoculated with an OTA- and FB(2)-producing strain of Aspergillus niger were analysed, but no analytes were detected. Analysis of 22 retail products showed one Parma meat with a very high level of OTA contamination (56-158 microg/kg) that clearly exceeded the Italian regulatory limit of 1 microg/kg. This sample and uninfected control samples were subsequently reanalysed, and the high OTA content was verified by two other techniques: (i) LC-time-of-flight MS confirmed the accurate mass as well as chlorine isotope pattern; and (ii) sample methylation in methanol-BF(3) and subsequent LC-MS/MS provided indirect confirmation by detection of the OTA methyl ester. In the contaminated Parma ham, the high OTA level most likely originated from growth of Penicillium nordicum on the meat.

Determination of mycophenolic acid in meat products using mixed mode reversed phase-anion exchange clean-up and liquid chromatography-high-resolution mass spectrometry.

A method for determination of mycophenolic acid (MPA) in dry-cured ham, fermented sausage and liver pâté is described. MPA was extracted from meat with bicarbonate-acetonitrile, further cleaned-up by mixed mode reversed phase-anion exchange and detected using a LC-MS system with electrospray ionisation-time-of-flight detection. The limit of detection was 4 microg/kg in sausage and 6 microg/kg in ham and pâté. The method was successfully used for quantification of MPA in dry-cured ham and liver pâté artificially inoculated with Penicillium brevicompactum. Levels ranged from 190 microg/kg in centre to 11 mg/kg in surface of ham and from 150 microg/kg in bottom to 14 mg/kg in surface of pâté.

Mycobiota in the processing areas of two different meat products.

Mould growth is not accepted on most types of North European meat products and is considered as both an economic and aesthetic problem for the producers. In order to determine the mycobiota in processing areas of fermented sausage and liver pâté, filamentous fungi were isolated from air, equipment and raw materials in the processing areas of two fermented sausage processing plants and two liver pâté processing plants. A total of 336 samples were examined. The diversity of filamentous fungi in the processing areas was high; at least 17 different genera were identified. The main isolated genera were identified as Aspergillus, Botrytis, Cladosporium, Epicoccum, Eurotium, Penicillium, Phaeoacremonium and Phoma. Of these, Penicillium and Eurotium were the most important for contamination of fermented sausage, whereas Penicillium and Cladosporium were most important for liver pâté. Cladosporium was isolated more frequently in the processing plants examined in the autumn than in the spring. The seasonal variation indicates that outdoor air is an important source for this contamination. Eurotium was isolated frequently at one of the fermented sausage plants. Penicillium was isolated frequently at all four processing plants and was in addition found on moulded meat products. Sixteen Penicillium species were identified. The most frequently isolated were P. brevicompactum and the closely related P. bialowiezense, P. solitum, P. palitans, P. fagi and a new, not described species named P. "milanense" (ined.; Frisvad, 2007 personal com.). Isolation of a new species illustrates that the mycobiota in the processing areas of North European meat products has not yet been intensively investigated. Several mycotoxin producing species were isolated; the most prevalent were P. brevicompactum/P. bialowiezense and P. palitans. A screening for secondary metabolites showed that isolates of these species consistently produced mycophenolic acid and cyclopiazonic acid, respectively. Presence of these toxinogenic species in the processing areas implies a risk of mycotoxin contamination of the products if they are or has been subjected to mould growth. The ochratoxin A producing species P. nordicum and P. verrucosum were not isolated during the study. It was concluded that Penicillium species are the most important contaminants of the meat products because of their high prevalence in the production environment, their presence on meat products and their toxinogenic properties.