Evaluation of Methods for Determination of Spore-Formers Responsible for the Late Gas-Blowing Defect in Cheese

Abstract

Late gas-blowing is a defect of European specialty cheeses caused by certain spore-forming bacteria of the genus Clostridiurn. Five most probable number methods for detecting spores were evaluated: a modified Weinzirl, NIZO-Ede, Fryer/Halligan, BB-lactate, and the BBlactate with modifications using pure cultures of C. butyricurn, C. sporogenes, and C. tyrobutyricum inoculated into sterile homogenized milk. Tubes containing media of the different methods were incubated for 14 d at 32C for C. butyricum and 37C for C. sporogenes and C. tyrobutyricurn. The modified Weinzirl and NIZO-Ede methods took the longest time to indicate gas formation (blowing) and detected the spore-formers less frequently. The Fryer/Halligan and BBlactate methods, which contain lactate, detected spores quicker. No apparent differences were observed between the Fryer/Halligan and BB-lactate methods.