Microbiological safety of traditional and starter-mediated processes for the manufacture of Italian dry sausage.

Microbiological changes occurring during the commercial manufacture of Italian dry sausages (Genoa and salametti) were studied in two urban Canadian centres over a 5 month period. A comparison was made between 6 plants which used bacterial starter cultures and 4 plants where more traditional processes (without starters) were used. A total of 600 samples of raw, fermented and finished products were tested for the presence of coliforms, salmonellae, staphylococci, streptococci, the rate of pH reduction and final water activity (aW). Numbers of total bacteria peaked earlier and were significantly higher in sausages at the fermentation stage produced with starter cultures than in those traditionally manufactured. This corresponded with a more rapid drop in pH of the starter-inoculated products. Staphylococci and streptococci were significantly higher in starter-fermented Genoa sausages at the fermentation stage, but no significant differences were seen in the microbiological content or aW of mature finished sausages manufactured by the two different techniques. Of 128 randomly chosen isolates of coagulase-positive staphylococci, 34.4% were enterotoxin producers and 80% of these produced type A toxin. Enterotoxigenic staphylococci were found in 2 different samples of finished salametti and one sample of finished Genoa made with starter cultures and in one sample of finished Genoa made without added culture. Total numbers of staphylococci in these samples were not greater than 500/g. No correlation between the method of manufacture and presence of enterotoxigenic staphylococci could be made. Five subsamples from one lot of raw Genoa were the only samples positive for Salmonella during this study. Results indicated that low temperature traditional fermentations can yield products which are as safe as those produced by the higher temperature starter-controlled process. One of the most important elements in the traditional process was believed to be the selection and use of raw materials of the highest possible quality.