Exposure of Listeria monocytogenes to a solution of sodium propionate (8% w/v) for 60 min caused 87% of the population to be injured. Injury was evidenced by inability of the bacterium to tolerate 6% sodium chloride in tryptose agar as compared to ability to grow on tryptose agar with no added salt. Injured cells were allowed to repair in tryptose broth and the repair process was studied by addition to tryptose broth of sublethal amounts of metabolic or synthetic inhibitors. Repair of injured cells did not require electron transport or synthesis of cell wall components, mRNA or protein. No changes which may have occurred in the cell membrane of injured cells, allowed leakage of proteins or nucleotides into the medium. Exogenous cation salts enhanced the rate of recovery of injured cells. The specific activity of lactic dehydrogenase was reduced in propionate-injured L. monocytogenes.

Colony Count, Microbial↗

PubMedDate not supplied

Rapid reverse phase liquid chromatographic determination of aflatoxin M1 in milk.

A rapid, economical, and reliable liquid chromatographic (LC) method is described for determination of aflatoxin M1 in milk. The method includes an improved AOAC extraction procedure, cleanup of the extract on a silica cartridge, and LC quantitation. Alternatively, a rapid column cleanup procedure can be used. Milk artificially spiked with aflatoxin M1 at 0.05, 0.1, and 0.5 ppb was analyzed using both new approaches as well as an AOAC method coupled with LC for quantitation of the toxin. Recovery of aflatoxin M1 by the first approach of the new method ranged between 93.4 and 99.1%, and for the alternative procedure between 92.4 and 96.8%. The AOAC method gave lower recovery (85.6-90.7%) of toxin, but the results from this method had a somewhat smaller standard deviation for replicate analyses than did results of the new method.

Aflatoxin M1↗

PubMedDate not supplied

Degradation of rubratoxin by Penicillium rubrum.

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Mycotoxins↗