Sodium bicarbonate (SB) inhibited the growth of bacteria and yeasts in agar media model systems under certain conditions. Escherichiu coli, Lactobacillus plantanrm, Staphylococcus aureus, and Pseudomonas aeruginosu aerobic plate counts were reduced lO,OOO-fold by 0.12M (1% wk) SB. Saccharomyces cerevisiae and Hansenula wingei were more sensitive; counts were reduced lOO,OOO-fold by 0.06M SB. Potassium bicarbonate was equally inhibitory, but equimolar sodium chloride had no effect, ruling out osmotic-and sodium-mediated mechanisms of inhibition. The bicarbonate ion was identified as the probable cause of SB-mediated inhibition although, in some cases, pH elevation played a significant role.
Toxin production by C. botulinurn type E was studied in cod, whiting, and flounder filets packaged in air-permeable film, vacuum packages and packages flushed with Nz or CO2 during storage at 8'; 12") or 26'C. Cod and whiting filets were flushed with CO2 and stored continuously at 4'C or cycled between 4" or 8' and 26°C. Cod and whiting fillets were flushed with gas mixtures and stored at 8'C or 26'C. Flounder deteriorated rapidly and was rejected by sensory evaluation prior to toxin detection during vacuum or modified atmosphere storage at 12"C and 8'C but after toxin detection at 26°C. Toxin was present either prior to or simultaneously with sensory rejection of cod and whiting fillets for all vacuum or modified atmosphere treatments and temperature regimens.
Recalls and/or outbreaks associated with Salmonella contamination in peanut-containing products were reported over the past several years. There are very limited data available on the prevalence and concentration of Salmonella on raw shelled peanuts in the United States. The objectives of this study were to estimate the prevalence of Salmonella on raw shelled peanuts in the United States and to estimate that concentration of Salmonella. Samples of Runner- and Virginia-type raw shelled peanuts from the 2008, 2009, and 2010 crop years were proportionately sampled from each growing region, based on 2007 production volume. Of 944 raw shelled peanut samples (375 g each), 22 (2.33%) were positive for Salmonella by the VIDAS Salmonella assay. Salmonella serovars identified in this study included Agona, Anatum, Braenderup, Dessau, Hartford, Meleagridis, Muenchen, Rodepoort, Tennessee, and Tornow. The concentration levels of Salmonella in positive samples, as determined by a most-probable-number assay, were <0.03 to 2.4 MPN/g. These data will be useful when designing and validating processes for the reduction or elimination of Salmonella in peanuts and/or peanut-containing products.
The number of commercially available kits and methods for rapid detection of foodborne pathogens continues to increase at a considerable pace, and the diversity of methods and assay formats is reaching a point where it is very difficult even for experts to weigh the advantages and disadvantages of different methods and to decide which methods to choose for a certain testing need. Although a number of documents outline quantitative criteria that can be used to evaluate different detection methods (e.g., exclusivity and inclusivity), a diversity of criteria is typically used by industry to select specific methods that are used for pathogen detection. This article is intended to provide an overall outline of criteria that the food industry can use to evaluate new rapid detection methods, with a specific focus on nucleic acid-based detection methods.
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