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

In raw seasoned sausages, coliforms represent one of the most important causes ofspoilage if they can grow to sufficiently high numbers, surviving through the seasoningprocess. The pH-value and the water activity value (aw) are the most importantpreservative 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 withnitrates and nitrites. Generally bacteria belonging to the Enterobacteriaceae family,such as Escherichia coli and Salmonella, do not tolerate high salt levels, but somespecies, such as Serratia rubidea, are very salt-tolerant (up to 10% NaCl) (Zambonelliet al., 1992). Halotolerant strains of Escherichia coli are able to survive and grow evenat very high salt concentrations. It seems that this high osmotic strength is due to theproduction of proline in the cells (Brewer, 2000; Tiecco, 2000). Several species ofSerratia, Proteus, Citrobacter, Hafnia, Enterobacter, Klebsiella and Escherichia coliare able to survive in raw seasoned sausages, and some of them may be able toproduce biogenic amines such as histamine and tyramine.The aim of this work was to study the NaCl tolerance and production of histaminein coliform strains isolated from raw seasoned sausages.[...]