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During the initial ripening period, yeasts (primarily Debaryomyces hansenii for semi-soft cheeses and additionally Geotrichum candidum for soft cheeses) and coagulase-negative staphylococci (Staphylococcus equorum) are present [3, 21, 26]. Generally, D. hansenii
and staphylococci on cheese surface are assumed to originate from the
cheese brine, which often is not changed or pasteurised between salting
of different batches [2, 3, 42]. For D. hansenii, Petersen et al. [46] showed that the dominating D. hansenii
strain on cheeses of the Danish Danbo type did not originate from the
added ripening culture, but from the dairy housemicrobiota present in
the ripening room. D. hansenii is important during
cheese ripening as it assimilates lactate and produces alkaline
metabolites such as ammonia thereby increasing pH of the cheese surface [23, 46], which enables the growth of the less acid tolerant bacterial microbiota, primarily Gram-positive coryneforms (Brevibacterium spp., Corynebacterium spp. and Microbacterium spp.) [4]. In addition, subpopulations of bacteria such as Gram-positive Marinilactibacillus spp. and Gram-negative Halomonas spp., Vibrio spp. and Proteus spp., and bacteria of the Enterobacteriaceae family have been reported to occur on cheese surfaces [14, 15, 25, 34, 35, 41, 50].
The presence of Gram-negative bacteria was first hypothesised to be
indicative of hygienic problems. However, more recent results have shown
that they produce important cheese flavour compounds and thus might
contribute positively to the cheese ripening process [11].
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