Microbial contamination of luncheon meat sliced and packaged at supermarkets in Porto Alegre, Brazil

Ano: 2011 | Volume: 39 | Número: 1

Autores: Vanessa Mottin, Elisa Fisch, Marisa Cardoso

Palavras-chave: ready-to-eat (rte) foods, luncheon meat, listeria, coliforms

Resumo Inglês:

Background: Ready-to-eat (RTE) foods are considered a high risk food group, since they are often consumed without a
cooking step. Luncheon meat, a RTE food widely consumed in Brazil, is traditionally produced as industrially vacuumpackaged
loaves and afterwards is sliced and re-packaged at retail stores. Since this practice may pose an additional hazard of
contamination, the purpose of this study was to evaluate total coliform counts (TCC), coagulase-positive staphylococci
counts (CPS), and the occurrence of Escherichia coli and Listeria sp. in luncheon meat samples sliced and packaged at
supermarkets.
Materials, Methods & Results: Three supermarket stores belonging to either regional or national chains located in Porto Alegre
were intentionally chosen, and luncheon meat samples were purchased from the same sampled stores weekly during a 20-week
period. In each sampling event, five store-packaged luncheon meat samples were obtained and analyzed. Individual samples (25
g) were homogenized, decimally diluted in buffered peptone water and submitted to TCC in Violet Red Bile Agar. Thermotolerant
coliform (FC) were confirmed in EC broth incubated at 45°C. Confirmed tubes were streaked on McConkey agar and submitted
to E.coli identification. Isolation and enumeration of coagulase-positive staphylococci (CPS) were performed on Baird-Parker
agar. The presence of Listeria sp. was tested in pooled samples submitted to pre-enrichment in University of Vermont (UVM)
Listeria Enrichment broth, followed by incubation in Fraser broth and isolation on tryptose agar with nalidixic acid and Palcam
agar. TCC mean varied from 1.2 log10 CFU.g-1 (store B) to 5.5 log10 CFU.g-1 (store C), while CPS mean counts were similar (0.63; 0.65
and 0.86 log10 CFU.g-1) for samples purchased at the three stores. Considering Brazilian standards for FCC, in stores A (n=6) and
C (n=8) samples considered unsafe (above 3log. g-1) were found, while all samples purchased at store B are considered sound
according to that standard. Moreover, three samples from each store (A and C) confirmed for the presence of E. coli. Samples
contaminated with Listeria sp. (n=16) were also found. Listeria monocytogenes was isolated from six samples, and was found
in all sampled supermarkets. A trend of Listeria sp. isolation frequency in samples with higher TCC was observed.
Discussion: The results demonstrated that bacteria may be introduced in luncheon meat during the slicing and packaging at
supermarkets. Our data are in accordance with other reports that indicate slicing as a critical control point of contamination and
transfer of pathogen, including L. monocytogenes, to foods during processing. Differences observed on extend of product
contamination may have resulted from variable levels of cleanliness during handling and slicing procedures at the three
supermarkets. Specifically, the cleaning of equipment surfaces represents a challenge for sanitation programs, since most
equipment is not hygienically designed and must be unassembled prior to sanitization procedures. This fact may lead to the
decrease of cleaning and disinfection frequency and to the hazard of biofilm formation. In conclusion, luncheon meat sliced and
packaged in supermarkets may pose a hazard to the consumers, and the adoption of more rigorous disinfection protocols for
equipment and surfaces in contact with ready-to-eat foods in these stores is advisable.