Survival of surface ripening cultures during storage and monitoring their development on cheese

AIMS: To study the survival of bacteria isolated from the surface of smear cheese and monitor their development during cheese ripening. METHODS AND RESULTS: The storage of five potential bacterial surface-ripening cheese cultures, Brevibacterium aurantiacum, Corynebacterium casei, Corynebacterium variable, Microbacterium gubbeenense and Staphylococcus saprophyticus, in maximum recovery diluent (MRD), containing 0.85% w/v or 5% w/v NaCl, at 21 or 4 degrees C for 40 days, was investigated. All five strains studied survived well with a maximum decrease of c. 2.5 log(10) CFU ml(-1) after storage for 40 days at 4 degrees C in 0.85% or 5% w/v NaCl. Survival, especially of C. variable, was less at 21 degrees C. The development of defined ripening cultures containing C. casei and Debaryomyces hansenii on two farmhouse cheeses was also evaluated. Using pulsed-field gel electrophoresis (PFGE) for the bacteria and mitochondrial DNA restriction fragment length polymorphism (mtDNA-RFLP) for the yeast, it was shown that the ripening cultures could be re-isolated in high numbers, 10(8) CFU cm(-2) for C. casei and 10(6) CFU cm(-2) for D. hansenii, from the cheese surface after 2.5 weeks of ripening. CONCLUSIONS: Ripening strains of surface ripening cultures can be stored in MRD containing 5% w/v salt at 4 degrees C for at least 40 days. Such cultures are recovered in high numbers from the cheese during ripening. SIGNIFICANCE AND IMPACT OF STUDY: This study has provided a low-cost and efficient way to store bacteria that could be used as ripening cultures for smear cheese. Such cultures can be recovered in high numbers from the cheese surface during ripening.