The BAB are a group of mainly spoilage bacteria that also belong to
the genus Clostridium, and have been referred to briefly above. This group of microbes is associated with the spoilage, through gas defects, of continental cheeses as a consequence of the fermentation of lactate to acetate, butyrate and hydrogen gas. Interestinglyother Clostridium spp. are the causative agents of “blown pack” spoilage of raw refrigerated vacuum packed meats. These Clostridium spp. are not BAB, and thus are not of concern to the dairy industry and, therefore, will not be discussed further. Clostridium species belonging to this group are also SRCs, and include the species C. butyricum, C. tyrobutyricum, and C. beijerinckii. The ability of some strains of C. butyricum to produce botulinum toxin makes the detection of this group of microbes in milk very important.
BAB contamination of milk and subsequently cheese has been attributed to dairy cow consumption of poor quality silage which has undergone aerobic deterioration, leading to insufficient acidification, and in turn, allowing for Clostridium spore germination and growth. High numbers of BAB spores have been isolated from grass and alfalfa silage, with low spore counts being observed in corn silage. It has been postulated that this is because grass silage is more likely to be contaminated with faeces than silage fermented from other substrates. Moreover, spore counts from silage originating from manure spread grass have been proven to be greater than those from grass fertilised with chemical fertiliser. Thus, the control of BAB spore counts in silage is necessary to in turn prevent the surface contamination of teats and limit BAB spore counts in BTM.