Occurrence of Clostridium spp. in ovine milk and Manchego cheese with late blowing defect: Identification and characterization of isolates

The presence of lactate-fermenting clostridial spores was investigated in 194 samples of raw bulk-tank ovine milk and in 57 Manchego cheeses with late blowing defect collected throughout one year from 55 factories. Spores were detected in 97% of milk samples analysed, with a most probable number (MPN) of 14.5 spores mL−1 and significantly (P < 0.001) higher counts in summer milk. The highest incidence of late blowing defect was also recorded for Manchego cheeses produced in summer. Out of 223 isolates from spoiled cheeses, 78.9%, 10.3%, 9.0% and 1.8% were identified as Clostridium sporogenes, Clostridium beijerinckii, Clostridium tyrobutyricum and Clostridium butyricum, respectively. Among seven bacteriocins produced by lactic acid bacteria, nisin A and Z were the only ones able to inhibit the growth of all Clostridium isolates.