Survival of Listeria monocytogenes in Galotyri, a traditional Greek soft acid-curd cheese, stored aerobically at 4 degrees C and 12 degrees C

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Survival of Listeria monocytogenes in Galotyri, a traditional Greek soft acid-curd cheese, stored aerobically at 4 degrees C and 12 degrees C (EN)

Rogga, K. J. (EN)

Πανεπιστήμιο Ιωαννίνων. Σχολή Θετικών Επιστημών. Τμήμα Χημείας (EL)
Rogga, K. J. (EN)

Galotyri is a traditional Greek soft acid-curd cheese, which is made from ewes' or goats' milk and is consumed fresh. Because cheese processing may allow Listeria monocytogenes post-process contamination, this study evaluated survival of the pathogen in fresh cheese during storage. Portions (0.5 kg) of two commercial types (<2% salt) of Galotyri, one artisan (pH 4.0+/-0.1) and the other industrial (pH 3.8+/-0.1), were inoculated with ca. 3 or 7 log cfu g(-1) of a five-strain cocktail of L. monocytogenes and stored aerobically at 4degreesC and 12degreesC. After 3 days, average declines of pathogen's populations (PALCAM agar) were 1.3-1.6 and 3.7-4.6 log cfu g(-1) in cheese samples for the low and high inocula, respectively. These declines were independent (P>0.05) of the cheese type or the storage temperature. From day 3, however, declines shifted to small or minimal to result in 1.4-1.8 log cfu g(-1) of survivors at 28 days of storage of all cheeses at 4degreesC, indicating a strong "tailing" independent of initial level of contamination. Low (1.2-1.7 log cfu g(-1)) survival of L. monocytogenes also occurred in cheeses at 12degreesC for 14 days, which were prone to surface yeast spoilage. When ca. 3 log cfu g(-1) of L. monocytogenes were inoculated in laboratory scale prepared Galotyri of pH congruent to4.4 and congruent to3 % salt, the pathogen died off at 14 and 21 days at 12degreesC and 4degreesC, respectively, in artisan type cheeses fermented with the natural starter. In contrast, the pathogen survived for 28 days in cheeses fermented with the industrial starter. These results indicate that L. monocytogenes cannot grow but may survive during retail storage of Galotyri despite its low pH of or slightly below 4.0. Although contamination of Galotyri with L. monocytogenes may be expected low (< 100 cfu g(-1)) in practice, that long-term survival of the pathogen in commercial cheeses was shown to be unaffected by the artificial contamination level (3 or 7 logs) and the storage temperature (4degreesC or 12degreesC), which should be a concern. (C) 2004 Elsevier Ltd. All rights reserved. (EN)

listeria monocytogenes (EN)

International Dairy Journal (EN)

Αγγλική γλώσσα


Elsevier (EN)

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