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Byline: T. Paarup (1), Juan Carlos Nieto (2), Carmen Pelaez (1), Juan Ignacio Reguera (2) Keywords: Key wordsaDry-cured ham; Deep spoilage; Serratia liquefaciens; Proteus vulgaris; Enterobacter cloacae Abstract: aThe microbiological and physico-chemical characteristics of dry-cured Spanish 'serrano' hams with deep spoilage were compared to unspoiled hams, and the evolution of similar characteristics was studied during the early curing stages of previously refrigerated or frozen hams. The results suggest a relationship between deep spoilage and the presence of Enterobacteriaceae, caused by insufficient NaCl concentrations during curing. Strains of Serratia liquefaciens, Enterobacter cloacae and Proteus vulgaris, which comprised the most frequently isolated species of enterobacteria from spoiled hams, were therefore characterised in a model system in order to examine their ability to grow in different NaCl concentrations at different temperatures. Strains isolated from normal hams during early curing stages and from the production environment were included for comparison. The results showed that all strains were able to grow in 7% NaCl at 5aadegC, and that strains isolated from spoiled hams did not differ from those isolated from normal hams and from the environment. The NaCl tolerance of strains isolated from spoiled hams was closely linked to incubation temperature, and a reduction in temperature from 5aadegC to 2aadegC reduced the tolerance significantly. Author Affiliation: (1) Instituto del Frio (CSIC), Ciudad Universitaria s/n, E-28040 Madrid, Spain e-mail: tpaarup@if.csic.es, ES (2) Faculty of Food Science and Technology and Chemical Science, University of Burgos, Plaza Misael Banuelos s/n, E-09001 Burgos, Spain, ES Article note: Received: 23 December 1998