Biochemical changes in Picón Bejes-Tresviso cheese, a Spanish blue-veined variety, during ripening

Microbial quality and presence of moulds in Kuflu cheese

The chemical and microbial qualities, including fungal flora, of 30 samples of Kuflu cheese randomly purchased from different markets in Turkey were investigated. The gross composition of the cheese samples ranged between 37.65-53.65% moisture, 6.21-40.09% fat-in-dry matter, 4.70-10.07% salt-in-moisture and 26.18-44.85% protein. The mean pH value of the cheeses was 6.29+/-0.28 and pH values ranged from 5.52 to 7.22. Variations between the samples in terms of their gross composition suggested a lack of quality standards in cheesemilk, cheesemaking procedure and ripening conditions. The levels of main microbial groups including total mesophilic and coliform bacteria, yeasts and moulds and the presence of some potentially pathogenic microorganisms (E. coli, Salmonella spp. and Staphylococcus aureus) were determined. The high numbers of all microbial groups and presence of potentially pathogenic organisms in the cheese samples suggested that the production and maturation of Kuflu cheese should be improved by better hygiene. Moulds at the cheese surface were isolated and identified. A total of 24 different mould species were detected and the genus most frequently isolated was Penicillium spp. which represented 70.25% of total isolates. Penicillium commune, P. roqueforti and P. verrucosum were the most abundant species in the cheeses sampled. The other dominant fungal groups were Geotrichum candidum, Penicillium expansum and P. chrysogenum. Other genera isolated from the cheese were Acremonium, Alternaria, Aspergillus, Cladosporium, Geotrichum, Mucor, Rhizopus and Trichoderma. The potentially toxigenic species, including some Penicillum spp. and Aspergillus flavus, were also detected.

Diversity of Geotrichum candidum strains isolated from traditional cheesemaking fabrications in France

The diversity of French fungus-ripened cheeses is due partly to the succession of fungi that colonize the cheese during ripening. Geotrichum candidum appears in the early stages of ripening on soft cheeses such as Camembert and semihard cheeses such as St. Nectaire and Reblochon. Its lipases and proteases promote flavor development, and its aminopeptidases reduce bitterness imparted by low-molecular-weight peptides in cheese. We assessed the genetic diversity of G. candidum strains by using random amplification of polymorphic DNA (RAPD)-PCR correlated with phenotypic tests for carbon assimilation and salt tolerance. Strains were isolated from milk, curd, and cheese collected in seven major cheesemaking regions of France. Sixty-four isolates were characterized. We found high genetic diversity of G. candidum even within the same cheesemaking regions. Strains did not group according to region. All of the strains from the Haute-Savoie were able to assimilate lactate as the sole source of carbon, while lactate assimilation varied among strains from the Auvergne. Strains varied in D-mannitol assimilation, and none used citrate as the sole source of carbon. Yeast-like colony morphology predominated in Reblochon, while all of the strains isolated from St. Nectaire were filamentous. The RAPD-PCR technique readily differentiated Geotrichum fragrans isolated from milk and curd in a St. Nectaire cheesemaking facility. This study reveals an enormous diversity of G. candidum that has been empirically selected through the centuries by the cheesemakers of France.