Stability and safety of traditional Greek salami -- a microbiological ecology study

Abstract

The microbiological and physicochemical changes which occurred during the industrial fermentation and ripening of four batches of Greek dry salami manufactured without starter cultures were followed. Moderated dehydration rates, monitored by slowly decreasing relative humidity from 94 to 90% during fermentation, prevented the production of insufficiently acidified batches by maintaining microbial activity for longer when the natural inoculum was low. The terminal pH values (5.0-5.2) and water contents (27.7-30.3%) of the sausages were narrowly ranged. Fermentation was governed by an active (> 10(8) cfu g(-1)) lactic flora, consisting of 'wild' strains of Lactobacillus sake. Gram-negative bacteria and aerobic sporeformers decreased below 10(2) and l0(3) cfu g(-1), respectively, while yeasts did not significantly increase during ripening and were below 10(5) cfu g(-1) in the ripened product. Sausages were substantially free of sulfite-reducing clostridia and coagulase-positive staphylococci during the whole process. Listeria spp., occurred in the fresh sausage mix, but disappeared from all batches at the latest by the end of fermentation. Enterococci exceeded 10(5) cfu g(-1) during the first days and remained at this level during ripening. Novobiocin-resistant staphylococci matching Staphylococcus saprophyticus (mainly) and S. xylosus dominated Micrococcaceae populations, ranged between 10(5) and 10(6) cfu g(-1). This is the first report of such a large contribution from S. saprophyticus to the production of dry salami of good quality. It is concluded that to keep or improve the traditional 'sensory type' of Greek salamis, suitable strains of L. sake, S. xylosus and possibly nitrate-reducing S. saprophyticus should be selected and validated as starter cultures in experimentally inoculated salamis.