SURVIVAL OF HEATED BACILLUS-COAGULANS SPORES IN A MEDIUM ACIDIFIED WITH LACTIC OR CITRIC-ACID

The influence of the intensity of heat treatments on the capacity of c itric or lactic acid to prevent growth of survivors of Bacillus coagul ans spores after 10 days storage at 35 degrees C was studied. In most cases, the number of survivors during storage decreased. The extent of this spore inactivation depended on the intensity of previous heat tr eatment and the pH of the medium and the acidulant used. The inactivat ing effect of storage was pronounced even at pH values less acidic tha n those used by the canning industry. Citric acid was more effective t han lactic acid on spores given only low heat treatments, but lactic w as more effective against those given more severe heat treatments. The severity of heat treatment required for lactic to be more effective t han citric acid increased with pH of the medium. Heat treatment also r equired increased pH for heated spores to grow. pH 4.6, regardless of acidulant used, was unable to prevent growth of unheated spores but a less acidic pH (pH 5.2) did prevent growth even when spores had been g iven only mild heat treatments (10 s at 100 degrees C). (C) 1997 Elsev ier Science B.V.