IDENTIFICATION OF CLOSTRIDIUM-TYROBUTYRICUM AS THE CAUSATIVE AGENT OFLATE BLOWING IN CHEESE BY SPECIES-SPECIFIC PCR AMPLIFICATION

Butyric acid fermentation, the late-blowing defect in cheese, caused b y the outgrowth of clostridial spores present in raw milk, can create considerable loss of product, especially in the production of semihard cheeses like Gouda cheese, but also in grana and Gruyere cheeses, To demonstrate the causative relationship between Clostridium tyrobutyric um and late blowing in cheese, many cheesemaking experiments were perf ormed to provoke this defect by using spores from several strains of t he major dairy-related clostridia, A method of PCR amplification of a part of the 16S rRNA gene in combination with hybridization with speci es-specific DNA probes was developed to allow the specific detection o f clostridial sequences in DNAs extracted from cheeses, The sensitivit y was increased by using nested PCR, Late blowing was provoked in expe rimental cheeses with 28 of the 32 C, tyrobutyricum strains tested, wh ereas experimental cheeses made with spores from C, beijerinckii, C, b utyricum, and C, sporogenes showed no signs of butyric acid fermentati on, In all experimental and commercial cheeses with obvious signs of l ate blowing, DNA from C, tyrobbutyricum was detected; in some cheeses, signals for C, beijerinckii were also found, It was concluded that on ly C, tyrobutyricum strains are able to cause butyric acid fermentatio n in cheese.