Assessment of safe enterococci as bioprotective cultures in low-acid fermented sausages combined with high hydrostatic pressure

Abstract

Three bacteriocinogenic, non-aminogenic and non-virulent Enterococcus strains (Enterococcus faecium CTC8005, Enterococcus devriesei CTC8006 and Enterococcus casseliflavus CTC8003) were used as starter cultures in low-acid fermented sausages to assess their competitiveness and their bioprotective potential against Listeria monocytogenes and Staphylococcus aureus. The inoculated strains were successfully monitored by RAPD-PCR. All the strains were able to grow, survive and dominate the endogenous enterococci population and avoided the growth of Enterobacteriaceae. E. devriesei CTC8006 and E. faecium CTC8005 particularly inhibited the growth of L. monocytogenes during the whole ripening process. S. aureus was not affected by the inoculated bacteriocinogenic enterococci strains. The application of high hydrostatic pressure (HHP) treatment (600 MPa for 5 min) at the end of ripening (day 21) produced an immediate reduction in the counts of Enterobacteriaceae to levels <1 log cfu/g and promoted a decrease of 1-log unit in the counts of S. aureus. E. faecium CTC8005, which reduced the counts of L. monocytogenes ca. 2 log cfu/g immediately after stuffing and in combination with HHP treatment promoted a further reduction of 1 log cfu/g in the pathogen counts. The combination of E. faecium CTC8005 and HHP was the most efficient antilisterial approach.