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Effect of storage at 4 and 10C on growth of listeria monocytogenes in and on Queso Fresco

Leggett, L. N., Tomasula, P. M., Van Hekken, D. L., Porto-Fett, A. C. S., Shoyer, B., Renye, J. A., Luchansky, J. B., Farkye, N.
Journal of food safety 2012 v.32 no.2 pp. 236-245
good manufacturing practices, cheesemaking, fresh cheeses, texture, salt content, monitoring, spoilage, models, manufacturing, storage temperature, pH, population density, water content, Listeria monocytogenes, safety assessment, anti-infective agents, food safety, pasteurized milk, bacteria
A five-strain rifampicin - resistant Listeria monocytogenes cocktail (ca. 3.0 loglOCFU/g) was introduced as a post-pasteurization contaminant in Queso Fresco (QF) that was manufactured using a commercial make procedure. L. monocytogenes was either inoculated into (IN) the curds before slicing or on (ON) the slices (52 to 66 g), individually vacuum - packaged and stored at 4C and IOC. Growth was monitored for up to 35 days. Gompertz analyses showed no differences in lag time (LT) because of temperature but growth rate (GR) and generation time (GT) were faster at IOC than 4C. After 20 days for both the IN and ON treatments, the maximum population density was 7.80 + 0.17 regardless of storage temperature. These results indicate that QF manufacture must be conducted using Good Manufacturing Practices and under hygienic conditions and that the use of antimicrobials and/or or post-processing interventions are necessary to prevent L. monocytogenes growth.