Development of defined surface starter cultures for the ripening of smear cheeses

For the surface ripened smear cheese varieties it is still general practice to use the mature smear of aged cheeses for the treatment of young cheeses (old-young smearing). The associated hygienic problems are obvious; saprophytic or pathogenic bacteria as well as moulds can become part of the house microflora and can persist over long periods of time by this in-house contamination cycle. This paper summarises studies of the past 8 years aiming to establish defined surface starters for the the ripening of Tilsit-type smear cheeses performed in the microbiology department of the Federal Dairy Research Center, Kiel, Germany and currently in a cooperative EU project (FAIR programme, CT98-4220, 1999-2001). Growth on cheese (lab scale) of the five strain minimal starter developed is now comparable to that of atypical old-young smear "starter". A complete smear layer is developed within 4-7 days. It consists of the yeast Debaryomyces hansenii, and the bacteria Brevibacterium linens, Arthrobacter nicotianae, Corynebacterium ammoniagenes, and Staphylococcus equorum. When defined starters were tested on pilot scale, a too weak sulphury volatile flavour was observed compared to the old-young smeared control cheeses. Some of the key sulphur components (methanethiol and derivatives), some alcohols and aldehydes were produced at lower levels by the defined starters. The development of typical light-brown cheese colour (so-called "red smear") was attributed to the interactions between yellow-pigmented Arthrobacter spp. and proteolytic bacteria. The orange pigments of B. linens and staphylococci were found to be of lesser importance. The role of Corynebacterium species which show fast growth, is still not clear. An impact of this predominant part of the smear flora on aroma- and colour development can be expected. However, clear effects were not observed in experiments in model systems. (C) 2002 Elsevier Science Ltd. All rights reserved.