Effect of NaCl concentration on the survival and growth of coliforms in raw seasoned sausages

摘要

In raw seasoned sausages, coliforms represent one of the most important causes of spoilage if they can grow to sufficiently high numbers, surviving through the seasoning process. The pH-value and the water activity value (a_w) are the most important preservative factors for slowing and then stopping the growth of these spoiling bacteria. As the seasoning process develops, the sausages become increasingly dehydrated, and the lower the water content of the products the higher is the NaCl concentration. In seasoned sausages the antimicrobial effect of NaCl acts in combination with nitrates and nitrites. Generally bacteria belonging to the Enterobacteriaceae family, such as Escheiichia coll and Salmonella, do not tolerate high salt levels, but some species, such as Serratia rubidea, are very salt-tolerant (up to 10% NaCl) (Zambonelli et al., 1992). Halotolerant strains of Escherichia coli are able to survive and grow even at very high salt concentrations. It seems that this high osmotic strength is due to the production of proline in the cells (Brewer, 2000; Tiecco, 2000). Several species of Serratia, Proteus, Citrobacter, Hafnia, Enterobacter, Klebsiella and Escherichia coli are able to survive in raw seasoned sausages, and some of them may be able to produce biogenic amines such as histamine and tyramine. The aim of this work was to study the NaCl tolerance and production of histamine in coliform strains isolated from raw seasoned sausages.