Growth factors affecting gas production and reduction potential of vegetative cell and spore inocula of dairy-related Clostridium species

Cheese late blowing defect caused by the Clostridium growth results in flavour and texture flaws and huge economical losses. The aim of this study was to evaluate simultaneously the influence of pH (6.50, 5.75, 5.00), NaCl (0, 1, 2, 4%) and temperature (10, 12, 15, 20, 37 degrees C) on gas production and reduction potential (Eh) of vegetative cell and spore inocula of dairy related clostridia (Clostridium beijerinckii, C. butyricum, C. sporogenes and C. tyrobutyricum). Clostridia showed a high reduction capacity in milk (E-h7min < -280 mV in 24 h). Spores exposed to harsh environment generated cells less sensitive to adverse conditions. A temperature <= 15 degrees C was effective in preventing the gas formation by vegetative cells for over 70 days, but a combination of temperature <= 15 degrees C, pH <= 5.00 and osmotic stress (NaCl 2%) or a temperature <= 10 degrees C was necessary to avoid spores outgrowth and gas production. Gas production resulting from C. tyrobutyricum spore germination and growth was not affected by acidity and salt concentration at 20 degrees C. Some strains of C. sporogenes were capable of producing gas even at 12 degrees C, pH 5.00 and 1% of NaCl. A ripening temperature below 10 degrees C represents a potential strategy to prevent LBD occurrence.