Staphylococcus aureus Growth and Enterotoxin Production during the Manufacture of Uncooked, Semihard Cheese from Cows' Raw Milk

Authors: Delbes, Celine¹; Alomar, Jomaa¹; Chougui, Nadia¹; Martin, Jean-François²; Montel, Marie-Christine¹

Source: Journal of Food Protection®, Volume 69, Number 9, September 2006 , pp. 2161-2167(7)

Publisher: International Association for Food Protection

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Abstract:

Staphylococcus aureus growth and enterotoxin production during the manufacture of model Saint-Nectaire, Registered Designation of Origin Saint-Nectaire, and Registered Designation of Origin Salers cheeses, three types of uncooked, semihard, raw milk cheese, were investigated. Coagulase-positive staphylococci (SC⁺) grew rapidly during the first 6 h. Between 6 and 24 h, counts increased by less than 0.5 log CFU/ml. Raw milk counts ranged from undetectable (<10 CFU/ml) to 3.03 log CFU/ml. Maximal levels reached in cheese on day 1 ranged from 2.82 to 6.84 log CFU/g. The level of SC⁺ after 24 h was mainly influenced by the milk baseline SC⁺ level (correlation coefficient, r > 0.80) but pH at 6 h influenced the SC growth observed between 6 and 24 h (r > 0.70). Thus, the initial level of SC⁺ in raw milk should be maintained below 100 CFU/ml and best below 40 CFU/ml. To limit growth, acidification should be managed to obtain pH values around or below 5.8 at 6 h in Saint-Nectaire cheeses and around or below 6.3 at 6 h in Salers cheeses. Enterotoxins were only detected in two Salers cheeses whose SC⁺ counts on day 1 were 5.55 log CFU/g and 5.06 log CFU/g, respectively, and whose pH values at 6 h were high (approximately 6.6 and 6.5, respectively).

Document Type: Research article

Affiliations: 1: INRA, Unité de Recherches Fromagères, Aurillac, F-15000 France 2: INRA, Unité de Recherche Maladies Métaboliques et Micronutriments, Saint-Gènes-Champanelle, F-63122 France

Publication date: 2006-09-01

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First published in 1937, the Journal of Food Protection^®, is a refereed monthly publication. Each issue contains scientific research and authoritative review articles reporting on a variety of topics in food science pertaining to food safety and quality. The Journal is internationally recognized as the leading publication in the field of food microbiology with a readership exceeding 11,000 scientists from 70 countries. The Journal of Food Protection^® is indexed in Index Medicus, Current Contents, BIOSIS, PubMed, Medline, and many others.

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Staphylococcus aureus Growth and Enterotoxin Production during the Manufacture of Uncooked, Semihard Cheese from Cows' Raw Milk

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