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Comparison of Methods for the Isolation of Salmonella Species from Lactic Casein
Author(s) -
POELMA PAUL L.,
ANDREWS WALLACE H.,
WILSON CLYDE R.
Publication year - 1981
Publication title -
journal of food science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.772
H-Index - 150
eISSN - 1750-3841
pISSN - 0022-1147
DOI - 10.1111/j.1365-2621.1981.tb15352.x
Subject(s) - lactose , casein , salmonella , food science , chemistry , incubation , isolation (microbiology) , lactic acid , rennet , bacteria , chromatography , incubation period , microbiology and biotechnology , biology , biochemistry , genetics
The efficiency of eight pre‐enrichment media (lactose broth, two modifications of lactose broth (added NaHCO 3 or added NaHCO 3 and brilliant green dye), lauryl tryptose broth, nutrient broth, buffered peptone water, trypticase soy broth, and chemically defined M‐9 medium) for recovering three Salmonella serotypes from casein was determined. Lowest Salmonella most probable numbers (MPNs) in artificially inoculated casein were found when samples were pre‐enriched in either modification of lactose broth. None of the other media consistently gave the highest Salmonella MPNs. When 35 and 43°C incubation temperatures were compared during the pre‐enrichment and selective enrichment stages of the isolation procedures, highest MPN values were obtained when 35°C was used throughout the analytical procedure. Blended casein homogenates required adjustment to pH 6.8 ± 0.2 for optimal recovery of Salmonella. Lactose broth used under these conditions of incubation temperature and pH adjustment generally resulted in methods sensitive enough to recover one Salmonella cell per gram of four types of casein (lactic, rennet, acid, and sodium caseinate).