Variability of microbial contamination of edible snail meat depending on species and place of their collection

摘要

The objective of the research was to determine the microbiological status of raw and frozen (cooked) snail meat obtained from both free-living and farmed edible snails. The research material comprised meat samples (10 g each) collected from three snail species, i.e. Roman snail (Helix pomatia - HP), small brown garden snail (Cornu aspersum aspersum - CAA) and large brown garden snail (Cornu aspersum maxima - CAM). Roman snails were collected in their natural environment in Greater Poland Voivodeship (region A: HPA) and Lower Silesian Voivodeship (region B: HPB). The Cornu genus snails were obtained from two different heliciculture farms in Greater Poland Voivodeship (farm A: CAA(A) and CAM(A)) and Lower Silesian Voivodeship (farm B: CAA(B) and CAM(B)). In both farms, snails were maintained under the mixed rearing system. Raw meat samples, taken from the edible portion of snails, that is, the foot with the collar and a fragment of the mantle, were obtained after the snails had been sacrificed in the laboratory. Frozen meat samples came from a snail meat processing facility. The samples were analyzed to determine the total aerobic bacterial count and the counts of Enterobacteriaceae, Escherichia coli, Enterococcus, Staphylococcus, Pseudomonas and Aeromonas, as well as psychotropic and proteolytic bacteria counts. Proteolytic bacteria were counted according to appropriate methodology, whereas the counts of other groups of microorganisms were obtained in accordance with the Polish Standards. Bacterial contamination levels (expressed as log cfu/g) were analyzed using the Statistica software (version 10.0). All values are presented as means and standard deviations. The total aerobic bacteria counts for HPA, HPB, CAA(A), CAM(A), CAA(B) and CAM(B) samples were, respectively, 5.78, 5.10, 6.00, 6.55, 5.12 and 5.21 log cfu/g in the case of raw meat, and 4.59, 4.75, 4.60, 5.13, 4.25 and 4.68 log cfu/g in the case of frozen meat. It was found that bacteria from the Enterobacteriaceae family were prevalent in both raw and frozen snail meat. The percentage of contaminated samples oscillated between 73.3% (HPB and CAM(B)) and 96.7% (CAA(A) and CAA(B)) for raw meat and between 20% (CAA(A)) and 100% (CAM(A)) for frozen meat. The quantitative contamination of raw meat with Enterobacteriaceae varied from 2.54 (HPB) to 4.75 log cfu/g (CAA(A)) and was higher by 1.0 to almost 2.0 log in farm snail meat as compared to Roman snail meat. The quantitative contamination of frozen meat was lower, ranging from 0.5 (HPA, CAA(A) and CAM(A)) to 1.65 log cfu/g (CAM(B)). All samples of raw and frozen snail meat were free from E. coli (contamination below 1 log cfu/g).