title: Occurrence and behavior of Bacillus cereus in naturally contaminated ricotta salata cheese during refrigerated storage.
abstract: The present study shows the fate of Bacillus cereus in refrigerated ricotta salata cheese during shelf-life. 144 ricotta salata cheese belonging to nine naturally contaminated batches were stored refrigerated and analyzed at 24 h, 30, 60 and 90 days of storage. Total bacterial count, B. cereus spores and vegetative forms, intrinsic properties and composition were determined. The presence of spores was sporadic while the prevalence and the level of B. cereus vegetative cells decreased respectively from 83.3 % to 4.65 ± 0.74 cfu g(-1) at the beginning of the observation period to 33.3 % and 1.99 ± 0.55 cfu g(-1) after 90 days. No information is currently available on the fate of B. cereus in ricotta salata. The production process of ricotta salata includes steps such as whey heating followed by slow cooling of clots, which expose to the risk of spore germination and successive growth to levels compatible with toxins production. The prolonged refrigerated storage was not favorable to sporulation, explaining the successive death of vegetative cells. The present study demonstrate the potential risk of food poisoning as consequence of pre-formed emetic toxins in ricotta salata. Food safety of ricotta salata relies on the rapid refrigeration of the product during critical phases for cereulide production.
authors.affiliation: Department of Veterinary Medicine, University of Sassari, Via Vienna 2, 07100, Sassari, Italy. Electronic address: cspanu@uniss.it.
authors.forename: Carlo
authors.initials: C
authors.lastname: Spanu
authors.affiliation: Department of Veterinary Medicine, University of Sassari, Via Vienna 2, 07100, Sassari, Italy.
authors.forename: Christian
authors.initials: C
authors.lastname: Scarano
authors.affiliation: Department of Veterinary Medicine, University of Sassari, Via Vienna 2, 07100, Sassari, Italy.
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Spanu
authors.affiliation: Department of Veterinary Medicine, University of Sassari, Via Vienna 2, 07100, Sassari, Italy.
authors.forename: Carlo
authors.initials: C
authors.lastname: Pala
authors.affiliation: Department of Veterinary Medicine, University of Sassari, Via Vienna 2, 07100, Sassari, Italy.
authors.forename: Daniele
authors.initials: D
authors.lastname: Casti
authors.affiliation: Department of Veterinary Medicine, University of Sassari, Via Vienna 2, 07100, Sassari, Italy.
authors.forename: Sonia
authors.initials: S
authors.lastname: Lamon
authors.affiliation: Department of Veterinary Medicine, University of Sassari, Via Vienna 2, 07100, Sassari, Italy.
authors.forename: Francesca
authors.initials: F
authors.lastname: Cossu
authors.affiliation: Department of Veterinary Medicine, University of Sassari, Via Vienna 2, 07100, Sassari, Italy.
authors.forename: Michela
authors.initials: M
authors.lastname: Ibba
authors.affiliation: Cooperativa Allevatori Ovini Formaggi Soc. Coop. Agricola, Loc. "Perda Lada" Fenosu, 09170, Oristano, Italy.
authors.forename: Gavino
authors.initials: G
authors.lastname: Nieddu
authors.affiliation: Department of Veterinary Medicine, University of Sassari, Via Vienna 2, 07100, Sassari, Italy.
authors.forename: Enrico P L
authors.initials: EP
authors.lastname: De Santis
mesh_terms: D001409:Bacillus cereus / Q000254:growth & development* / Q000502:physiology; D002611:Cheese / Q000382:microbiology*; D047630:Depsipeptides / Q000378:metabolism; D005506:Food Contamination; D005516:Food Microbiology; D061353:Food Storage; D005517:Foodborne Diseases; D012034:Refrigeration
chemical_list: D047630:Depsipeptides; C089294:cereulide
keywords: Bacillus cereus; Sheep's milk; Whey cheese