Microbiological and physico-chemical characterisation of deep spoilage in Spanish dry-cured hams and characterisation of isolated Enterobacteriaceae with regard to salt and temperature tolerance

The microbiological and physico-chemical characteristics of dry-cured Spani sh "serrano" hams with deep spoilage were compared to unspoiled hams, and t he evolution of similar characteristics was studied during the early curing stages of previously refrigerated or frozen hams. The results suggest a re lationship between deep spoilage and the presence of Enterobacteriaceae, ca used by insufficient NaCl concentrations during curing. Strains of Serratia liquefaciens, Enterobacter cloacae and Proteus vulgaris, which comprised t he most frequently isolated species of enterobacteria from spoiled hams, we re therefore characterised in a model system in order to examine their abil ity to grow in different NaCl concentrations at different temperatures. Str ains isolated from normal hams during early curing stages and from the prod uction environment were included for comparison. The results showed that al l strains were able to grow in 7% NaCl at 5 degrees C, and that strains iso lated from spoiled hams did not differ from those isolated from normal hams and from the environment. The NaCl tolerance of strains isolated from spoi led hams was closely linked to incubation temperature, and a reduction in t emperature from 5 degrees C to 2 degrees C reduced the tolerance significan tly.