Behavior of Listeria monocytogenes in the presence of cocoa carrageenan, and sugar in a milk medium incubated with and without agitation
Enhanced growth of Listeria monocytogenes strain V7 in chocolate milk rather than skim milk was further investigated by testing various concentrations of cocoa powder (two types of Dutch-process, designated A and B), cane sugar, and sodium carrageenan in skim milk at 13 and 30 grade centigrade with and without agitated incubation. Increasing sugar concentrations (0, 6.5 and 12.0 percent) were marginally significant (p equal 0.06) in shortening generation times (5.17, 5.07 and 5.05 h, respectively) of the pathogen. Maximum populations attained by the pathogen were greater when cocoa (0.75 percent type A or B) and sugar (6.5 or 12.0 percent) were present. Sugar concentration affected growth of L. monocytogenes in an approximately linear relationship (8.41, 8.67, 8.82 log 10 CFU/ml for 0, 6.5 and 12.0 percent sugar, respectively) except in samples containing only carragenan. In this instance, presence of 6.5 and 12.0 percent sugar resulted in equivalent maximum populations (8.54 and 8.52 log 10 CFU/ml). Three factors enhanced growth of the pathogen at 30 grade centigrade: addition of cocoa, addition of sugar, and agitated rather than quiescent incubation. Without cocoa, generation times of L. monocytogenes were longer (1.04 h) compared to presence of type A (0.87 h) or B (0.90 h) cocoa. L. monocytogenes in agitated samples had shorter (0.82 h) generation times than in quiescent cultures (0.95 h). Highest populations were attained in agitated samples containing sugar and type A (9.21 log 10 CFU/ml) or type B (9.22 log 10 CFU/ml) cocoa compared to lowest populations in quiescent samples of skim milk (8.56 log 10 CFU/ml).
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| Format: | biblioteca |
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Ene
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| Subjects: | CACAO, CACAO EN POLVO, CARRAGENINAS, AZUCAR, LISTERIA MONOCYTOGENES, BACTERIA, AGITACION, BACTERIOSIS, POLUCION, |
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| Summary: | Enhanced growth of Listeria monocytogenes strain V7 in chocolate milk rather than skim milk was further investigated by testing various concentrations of cocoa powder (two types of Dutch-process, designated A and B), cane sugar, and sodium carrageenan in skim milk at 13 and 30 grade centigrade with and without agitated incubation. Increasing sugar concentrations (0, 6.5 and 12.0 percent) were marginally significant (p equal 0.06) in shortening generation times (5.17, 5.07 and 5.05 h, respectively) of the pathogen. Maximum populations attained by the pathogen were greater when cocoa (0.75 percent type A or B) and sugar (6.5 or 12.0 percent) were present. Sugar concentration affected growth of L. monocytogenes in an approximately linear relationship (8.41, 8.67, 8.82 log 10 CFU/ml for 0, 6.5 and 12.0 percent sugar, respectively) except in samples containing only carragenan. In this instance, presence of 6.5 and 12.0 percent sugar resulted in equivalent maximum populations (8.54 and 8.52 log 10 CFU/ml). Three factors enhanced growth of the pathogen at 30 grade centigrade: addition of cocoa, addition of sugar, and agitated rather than quiescent incubation. Without cocoa, generation times of L. monocytogenes were longer (1.04 h) compared to presence of type A (0.87 h) or B (0.90 h) cocoa. L. monocytogenes in agitated samples had shorter (0.82 h) generation times than in quiescent cultures (0.95 h). Highest populations were attained in agitated samples containing sugar and type A (9.21 log 10 CFU/ml) or type B (9.22 log 10 CFU/ml) cocoa compared to lowest populations in quiescent samples of skim milk (8.56 log 10 CFU/ml). |
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