The surface flora of bacterial smear-ripened cheeses from cow's and goat'smilk

Debaryomyces vees hansenii was found to be the predominant yeast in all sta ges of ripening in several studies on semi-hard Tilsit cheese, soft Chaumes cheese and semi-hard goat's cheese. 75-95% of the bacterial flora was made up of coryneform bacteria. Brevibacterium linens was found at 0-15%. Yello w pigmented coryneform isolates (1-30%) belonged to Arthrobacter nicotianae . Non pathogenic staphylococci (mainly Staphylococcus equorum) were found a t 5-15% of the total flora. Model systems were used to study the microbial interactions for growth, colour and aroma development within the surface fl ora to be able to formulate a defined starter culture. Commercially available surface starters do not reflect the microbial compos ition of the cheese surface. Too much emphasis is put on B. linens because of the orange pigmentation. New results showed that the red-brown or orange pigments are most likely due to the yellow pigmented Arthrobacter sp. in t he surface flora. The mechanisms of developing the different shades of red are not yet understood. B. linens may be more important for aroma developme nt, due to a highly efficient sulfur metabolism which also affects colour d evelopment. The importance of commercial S, xylosus is not clear since S. e quorum was predominant instead, on all cheese varieties analysed. Brines we re determined to be a natural reservoir for salt-tolerant S. equorum. The s uccessful use of a defined 5-strain starter (D. hansenii, B. linens, A. nic otianae, Corynebacterium ammoniagenes and S. sciuri) for Tilsit cheese ripe ning was demonstrated on a 10 kg scale. Further improvement is currently be ing tested within an EU funded project. (C) 2001 Elsevier Science Ltd. All rights reserved.