Moulds contaminants on Norwegian dry-cured meat products.

Dry-cured meat production has a long tradition in Norway. However, uncontrolled mould growth on the surface of the dry-cured meat products is causing significant quality problems. As some moulds are mycotoxigenic, their growth on the dry-cured meat products could also pose a serious health risk. Such quality problems and potential health risks can be better handled if the types of moulds growing on the products are known. In total, 161 samples were collected from the ripening and packaging stages of production with the aim of identifying moulds contaminating smoked and unsmoked Norwegian dry-cured meat products. Moulds were isolated either by transferring aerial mycelium of each visible mould colonies on the products or by directly plating pieces of meat on suitable agar media. The isolates were identified at a species level by a polyphasic approach. In total, 264 isolates belonging to 20 species and four fungal genera were identified. The genus Penicillium covered 88.3% of the total isolates. This genus contributed to the isolates of smoked and unsmoked products by 91% and 84% respectively. Penicillium nalgiovense was the dominant species isolated from both smoked and unsmoked products and covered 38% of the total isolates. Penicillium solitum and P. commune were the next most frequently isolated species with a contribution of 13% and 10% respectively. Species of Cladosporium and Eurotium contributed to the total isolates by 6% and 4.9% respectively. Smoking seems to affect the growth of these dominating species differently. An increase in the isolation frequency of P. nalgiovense accompanied by the reduction in the occurrence of P. solitum, P. commune and species of Cladosporium was observed on smoked products. The survey showed that the species of Penicillium are associated with Norwegian dry-cured meat products in general. Penicillium nalgiovense, the dominating mould species, is a potential producer of penicillin and its presence could represent a threat to allergic consumers.

Yeast diversity and dynamics in the production processes of Norwegian dry-cured meat products.

This study investigate the diversity and dynamics of yeasts in the production processes of one unsmoked and two smoked dry-cured meat products of a Norwegian dry-cured meat production facility. A longitudinal observational study was performed to collect 642 samples from the meat, production materials, room installations and indoor and outdoor air of the production facility. Nutrient rich agar media were used to isolate the yeasts. Morphologically different isolates were re-cultivated in their pure culture forms. Both classical and molecular methods were employed for species identification. Totally, 401 yeast isolates belonging to 10 species of the following six genera were identified: Debaryomyces, Candida, Rhodotorula, Rhodosporidium, Cryptococcus and Sporidiobolus. Debaryomyces hansenii and Candida zeylanoides were dominant and contributed by 63.0% and 26.4% respectively to the total isolates recovered from both smoked and unsmoked products. The yeast diversity was higher at the pre-salting production processes with C. zeylanoides being the dominant. Later at the post-salting stages, D. hansenii occurred frequently. Laboratory studies showed that D. hansenii was more tolerant to sodium chloride and nitrite than C. zeylanoides. Smoking seems to have a killing or a temporary growth inhibiting effect on yeasts that extend to the start of the drying process. Yeasts were isolated only from 31.1% of the environmental samples. They belonged to six different species of which five of them were isolated from the meat samples too. Debaryomyces hansenii and Rhodotorula glutinis were dominant with a 62.6% and 22.0% contribution respectively. As none of the air samples contained D. hansenii, the production materials and room installations used in the production processes were believed to be the sources of contamination. The dominance of D. hansenii late in the production process replacing C. zeylanoides should be considered as a positive change both for the quality and safety of the products, as C. zeylanoides has been documented as an emerging pathogen.

Biofilm formation and the presence of the intercellular adhesion locus ica among staphylococci from food and food processing environments.

In clinical staphylococci, the presence of the ica genes and biofilm formation are considered important for virulence. Biofilm formation may also be of importance for survival and virulence in food-related staphylococci. In the present work, staphylococci from the food industry were found to differ greatly in their abilities to form biofilms on polystyrene. A total of 7 and 21 of 144 food-related strains were found to be strong and weak biofilm formers, respectively. Glucose and sodium chloride stimulated biofilm formation. The biofilm-forming strains belonged to nine different coagulase-negative species of Staphylococcus. The icaA gene of the intercellular adhesion locus was detected by Southern blotting and hybridization in 38 of 67 food-related strains tested. The presence of icaA was positively correlated with strong biofilm formation. The icaA gene was partly sequenced for 22 food-related strains from nine different species of Staphylococcus, and their icaA genes were found to have DNA similarities to previously sequenced icaA genes of 69 to 100%. Northern blot analysis indicated that the expression of the ica genes was higher in strong biofilm formers than that seen with strains not forming biofilms. Biofilm formation on polystyrene was positively correlated with biofilm formation on stainless steel and with resistance to quaternary ammonium compounds, a group of disinfectants.