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A new procedure for surface contamination of food products using absorbent paper
Author(s) -
Tucci Patrizia,
Sperandii Anna Franca,
Salini Romolo,
Centorotola Gabriella,
Neri Diana,
Iannetti Luigi,
Migliorati Giacomo,
Pomilio Francesco
Publication year - 2018
Publication title -
journal of food safety
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.427
H-Index - 43
eISSN - 1745-4565
pISSN - 0149-6085
DOI - 10.1111/jfs.12461
Subject(s) - contamination , listeria monocytogenes , homogeneous , food science , homogeneity (statistics) , environmental science , suspension (topology) , pulp and paper industry , mathematics , chemistry , biology , bacteria , engineering , ecology , genetics , statistics , pure mathematics , combinatorics , homotopy
Abstract A new method was developed for artificial contamination of food products during challenge test studies, in products where superficial contamination is needed. Rinds of Gorgonzola cheese wheels were divided into quarters and then squares with 12 cm of side and contaminated with absorbent paper soaked with a bacterial suspension of Listeria monocytogenes left in contact with the surface of the blue‐veined cheese, in order to achieve homogenous contamination of the whole surface. To verify the performance of the method of contamination, after 24 hr L. monocytogenes was enumerated to evaluate surface contamination. With the method described, an average concentration of about 5 log 10 cfu/cm 2 or MPN/cm 2 was obtained starting from a contaminated suspension of 8 log 10 cfu/ml. The homogeneity of the contamination was demonstrated by the application of statistical tests. Practical applications Challenge tests are carried out to simulate contaminations as they happen during the processing and aging of cheeses, cured meats or ready‐to‐eat foods, for cross contamination studies, for applications of predictive microbiology, and to evaluate potential dragging of bacteria during the cutting of slices. In all cases, the inoculum should be applied on the product using the appropriate technique, in order to mimic natural contamination. This study reports a new method of contamination that allows the achievement of homogeneous microbial distribution on the whole flat surface of foods, using absorbent paper soaked with a bacterial suspension of Listeria monocytogenes . It was tested in the framework of challenge tests aimed to quantify the dragging of bacteria from Gorgonzola cheese rinds to paste during different processing steps. The procedure could be, however, profitably used also in other food products, when uniform surface contamination is required.