The Effect of Nisin on Growth Kinetics from Activated Bacillus cereus Spores in Cooked Rice and in Milk
Abstract:The growth kinetics of germinated cells from activated spores of Bacillus cereus in cooked white rice and in milk were evaluated at different temperatures for control samples and for samples with 25 μg of nisin per ml added. Nisin was applied in the form of Nisaplin (106 IU/g), which contained 25,000 μg of nisin per g. The length of the lag phase for cooked white rice controls was 120 h at 10°C, 8 h at 25°C, and 2.5 h at 33°C. The generation times for cooked rice were 327.7 min at 10°C, 59.0 min at 25°C, and 42.3 min at 33°C; those for milk without nisin were 297.0 min at 20°C, 31.2 min at 30°C, 28.6 min at 35°C, and 33.7 min at 40°C; and those for milk with nisin added were 277.2 min at 20°C, 66.9 min at 30°C, and 66.4 min at 35°C. No development of B. cereus was observed for milk with nisin added at 40°C for 12 h, in which germinated cells decreased by a decimal reduction time (D) of 4.7 h. A temperature of 45°C was shown to be harmful to B. cereus, decreasing the germinated cells in both formulations with D-values of 4.3 to 4.6 h. Similar inhibition of cell growth at 40°C was not observed with lower nisin concentrations.
Document Type: Research Article
Affiliations: 1: Department of Pharmaceutical Technology, School of Pharmaceutical Sciences, University of São Paulo, Rua Antonio de Macedo Soares, 452, São Paulo 04607-000, Brazil 2: Department of Pharmaceutical Technology, School of Pharmaceutical Sciences, University of São Paulo, Rua Antonio de Macedo Soares, 452, São Paulo 04607-000, Brazil
Publication date: 2002-02-01
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