The Behaviour of a Food Poisoning Strain of <i>Clostridium welchii</i> in Beef

Abstract

S ummary : An inoculum of 10 5 spores of Clostridium welchii F2985/50 in meat survived steaming at 100° for 5 h, the number being reduced sevenfold for every hour of steaming. They also survived for at least 6 months in frozen meat stored at ‐5° and ‐20°, whereas vegetative cells died more rapidly at ‐5° than at ‐20°. In beef stored for 13 days at 1°, 5°, 10° and 15° there was no multiplication but a slow destruction of vegetative cells, but there was little change in the spore count. Slow multiplication occurred at 20° but at 25° and 37° growth was rapid. Only about 3% of the spores germinated without prior heat shock, so the majority failed to germinate in raw meat stored at any temperature, but did so once the meat had been heated. In meat which had been heated and allowed to cool almost all of the spores had lost their heat resistance. It was found that the minimal growth temperature was related to pH and medium, so that meat with a pH higher than that used in these experiments (pH 5°7–5°8) would probably have a lower minimal growth temperature for these organisms and would thus be more susceptible to spoilage.